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Mediterranean winter rainfall in phase with African monsoon during past 1.36 million
years
Bernd Wagner1*†, Hendrik Vogel2†, Alexander Francke1,3, Tobias Friedrich4, Timme
Donders5, Jack H. Lacey6, Melanie J. Leng6,7, Eleonora Regattieri8,9, Laura Sadori10, Thomas
Wilke11, Giovanni Zanchetta8, Christian Albrecht11, Adele Bertini12, Nathalie CombourieuNebout13, Aleksandra Cvetkoska5, 11, Biagio Giaccio14, Andon Grazhdani15, Torsten Hauffe11,
Jens Holtvoeth16, Sebastien Joannin17, Elena Jovanovska11, Janna Just1,18, Katerina Kouli19,
Ilias Kousis20, Andreas Koutsodendris20, Sebastian Krastel21, Niklas Leicher1, Zlatko
Levkov22, Katja Lindhorst21, Alessia Masi10, Martin Melles1, Anna M. Mercuri23, Sebastien
Nomade24, Norbert Nowaczyk25, Konstantinos Panagiotopoulos1, Odile Peyron17, Jane M.
Reed26, Leonardo Sagnotti27, Gaia Sinopoli10, Björn Stelbrink11, Roberto Sulpizio28, 29, Axel
Timmermann30,31, Slavica Tofilovska22, Paola Torri32, Friederike Wagner-Cremer5, Thomas
Wonik33, Xiaosen Zhang34
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Institute of Geology and Mineralogy, University of Cologne, Cologne, Germany.
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16
2
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20
4
International Pacific Research Center, University of Hawaii at Manoa, Honolulu, Hawaii,
USA.
23
6
Institute of Geological Sciences & Oeschger Centre for Climate Change Research,
University of Bern, Bern, Switzerland.
School of Earth, Atmospheric, and Life Science, University of Wollongong, Wollongong,
Australia.
Palaeoecology, Department of Physical Geography, Utrecht University, Utrecht, The
Netherlands.
National Environmental Isotope Facility, British Geological Survey, Nottingham, UK.
24
25
7
26
8
29
10
27
28
Centre for Environmental Geochemistry, School of Biosciences, University of Nottingham,
UK.
Dipartimento di Scienze della Terra, University of Pisa, Pisa, Italy.
9
Institute of Earth Sciences and Earth Resources-Italian National Research Council (IGGCNR), Pisa, Italy.
Dipartimento di Biologia Ambientale, Università di Roma "La Sapienza", Rome, Italy.
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31
11
32
12
35
14
Istituto di Geologia Ambientale e Geoingegneria – CNR, Rome, Italy.
Department of Animal Ecology & Systematics, Justus Liebig University Giessen, Giessen,
Germany.
Dipartimento di Scienze della Terra, Università di Firenze, Firenze, Italy.
13
33
34
CNRS UMR 7194, Muséum National d’Histoire Naturelle, Institut de Paléontologie
Humaine, Paris, France.
15
Faculty of Geology and Mineralogy, University of Tirana, Albania.
37
16
School of Chemistry, University of Bristol, Bristol, UK.
40
18
36
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39
17
CNRS UMR 5554, Institut des Sciences de l’Evolution de Montpellier, Université de
Montpellier, Montpellier, France.
Fachbereich Geowissenschaften, Universität Bremen, Bremen, Germany.
1
19
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42
Faculty of Geology and Geoenvironment, National and Kapodistrian University of Athens,
Athens, Greece.
45
21
Institute of Geosciences, Christian-Albrechts-Universität zu Kiel, Kiel, Germany.
46
22
University Ss Cyril and Methodius, Institute of Biology, Skopje, FYROM.
49
50
24
53
26
43
44
20
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48
23
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25
Paleoenvironmental Dynamics Group, Institute of Earth Sciences, Heidelberg University,
Heidelberg, Germany.
Dipartimento di Scienze della Vita, Laboratorio di Palinologia e Paleobotanica, Università
di Modena e Reggio Emilia, Modena, Italy.
Laboratoire des Sciences du Climat et de l’Environnement, UMR 8212, CEA/CNRS/UVSQ
et Université Paris-Saclay, Gif-Sur-Yvette, France.
Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Potsdam,
Germany.
The Department of Geography, Geology and Environment, University of Hull, Hull, UK.
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27
Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy.
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28
Dipartimento di Scienze della Terra e Geoambientali, University of Bari, Bari, Italy.
29
IDPA-CNR, Milan, Italy.
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30
Center for Climate Physics, Institute for Basic Science, Busan, South Korea
58
31
Pusan National University, Busan, South Korea
61
33
Leibniz Institute for Applied Geophysics (LIAG), Hannover, Germany.
62
34
Institute of Loess Plateau, Shanxi University, Taiyuan, China.
64
*Correspondence to: wagnerb@uni-koeln.de.
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† these authors contributed equally to this work.
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63
32
Dipartimento di Scienze della Vita, Laboratorio di Palinologia e Paleobotanica, Università
di Modena e Reggio Emilia, Modena, Italy.
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2
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Precipitation is a key factor for socioeconomic development in densely populated and summer
70
difficult to project accurately. While current climate model simulations indicate a progressive
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well constrained1. Only a few continental proxy records capable of capturing hydroclimate
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underlying orbital geometries, necessary to validate climate model data on Quaternary time
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transient climate model hind cast, to show that high winter precipitation anomalies occur
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activity. While this is counter-intuitive at first sight, our data suggest that increased sea-
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pressure systems entering the Mediterranean during phases characterized by low continental
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dry regions such as the Mediterranean realm. Seasonal and regional changes are critical, but
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summer drying over the next century, precipitation changes during winter months are less
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change cover multiple Northern Hemisphere summer insolation maxima2,3 with different
75
scales. Here we use a 1.36 million year proxy time series from Lake Ohrid, coupled to a long
77
during phases with strong seasonal contrast in insolation and high African summer monsoon
79
surface temperatures amplify local cyclogenesis while also refuelling North Atlantic low
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ice volume and high atmospheric CO2 concentrations. Comparison with modern reanalysis
83
to those driving the reconstructed precipitation increases. Our extended record covers multiple
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performance.
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data shows that current drivers of rainfall amount in the Mediterranean share some similarities
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insolation maxima and therefore is an important benchmark for testing climate-model
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Mediterranean climates are characterized by strong seasonal contrasts between dry and warm
summers, and wet and mild winters. The amount and temporal extent of precipitation during
the winter half-year (October through March) determines the prevailing type of vegetation
and water availability for agrarian land-use in the Mediterranean borderlands. In recent
decades, reduction of winter precipitation has become a regular phenomenon in this region,
3
93
with anthropogenic greenhouse gas (GHG) and aerosol forcing identified as potential
95
Pathway (RCP) 4.5 and 8.5 scenarios, predict a progressive summer drying over the next
97
well constrained, with different simulation runs showing trends both towards wetter and drier
99
current modelling approaches are useful for decision makers5,6.
94
contributors4. Current climate model simulations, using the Representative Concentration
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century1. Precipitation changes during the Northern Hemisphere (NH) winter months are less
98
conditions. The uncertainty in winter precipitation projections limits the extent to which
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Long-term, empirical baseline data are helpful to constrain uncertainties in climate
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modelling proxy records. Proxy records and modelling experiments suggest that enhanced
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intertropical convergence zone (ITCZ) and increase in African monsoon strength during
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winter insolation (NHWI) minima2,7,8,9. However, most continental records that are capable of
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orbital geometries. In fact, the majority of records are limited to the Holocene10,11, yet the
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interglacials, due to lower eccentricity. Terrestrial proxy time series covering multiple NHSI
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Mediterranean Sea provide continuity throughout the Plio-Pleistocene and capture cessations
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layers12,13. While multiple factors contribute to sapropel formation, increased freshwater
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considered the most important14,15. Hence, the Mediterranean sapropel record is thought to be
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a direct indicator of precipitation in, and runoff from, the entirety of the Mediterranean realm.
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precipitation in the Mediterranean region is in phase with the northward shift of the
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precession minima causingNorthern Hemisphere summer insolation (NHSI) maxima and
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capturing hydroclimate change do not cover multiple NHSI maxima with different underlying
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Early Holocene NHSI maximum was relatively weak compared to most other Quaternary
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maxima from the Mediterranean region are scarce2,3. Sediment records from the
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of deep-water ventilation associated with the formation of prominent, organic-rich sapropel
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input, particularly from the African continent during NHSI-forced monsoon maxima, is
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an excellent indicator of the relative timing of increased African monsoon strength rather than
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Reconstructed precipitation increases in the northern Mediterranean borderlands during
4
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sapropel formation have been interpreted to be a product both of intensified summer and
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stronger wintertime storm tracks2 or air-sea temperature difference, and locally induced
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Alternatively, conceptual models based on proxy time series have suggested increases in the
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winter precipitation15,16. Modelling experiments explain increased winter precipitation by
convective precipitation that dominate freshwater budget changes on obliquity time scales17.
frequency and intensity of low-pressure systems evolving in the Mediterranean region, mostly
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during fall and early winter7,8,16. Hence, a well-dated proxy record covering multiple glacial-
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addressing long-standing questions regarding the underlying mechanisms, timing, and
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concentration, orbital geometries, continental ice sheet volume and extent).
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Myr sedimentary record from Lake Ohrid (Fig. 1, Extended Data Fig. 1). Climate variations at
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We compare our sedimentary proxy time series with transient climate simulation data and
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variability and seasonality, as well as phase relationships to orbital forcing.
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primarily fed by an extensive karst aquifer system, which supplies ions (mainly Ca2+ and
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m-long composite sediment succession from the lake centre, comprised of fine-grained hemi-
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with no evidence of unconformities or erosion surfaces. Independent age control from 16
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Fig. 2, Extended Data Table 1, Extended Data Table 2) provides a robust chronological
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interglacial cycles and being sensitive to changes in Mediterranean hydroclimate is key to
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amplitude of precipitation variability under different climate boundary conditions (GHG
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Here, we assess precipitation variability in a continuous, independently dated 1.36
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this site represent broader climate variability across the northern Mediterranean borderlands18.
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prominent monsoon records, to provide a mechanistic understanding of precipitation
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Lake Ohrid is of tectonic origin and 293 m deep. The lake is hydrologically open and
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HCO3-) to the lake and filters particulate matter19. Scientific drilling in 2013 resulted in a 584-
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pelagic muds in the upper 447 m18,20. Sedimentation is thought to have been uninterrupted,
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interspersed tephra layers in combination with magnetostratigraphy (Fig. 1, Extended Data
5
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framework. This framework allows us to match changes in orbital parameters with our proxy
146
spans the last 1.36 Myr (Fig. 1).
148
excluding pine (AP-P), deciduous oaks), and hydrological variability (total inorganic carbon
150
precessional (~21 ka) component (Fig. 2; Extended Data Figs 3, 4, and 5). During periods of
152
hydrological and vegetation proxy data (Fig. 2). We interpret these peaks in TIC (mainly from
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activity of, and ion supply from, the karst aquifers combined with higher aquatic productivity
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data to refine the age-depth relationships. The data demonstrate that the Lake Ohrid record
Indicators for detrital input (quartz, potassium), catchment vegetation (arboreal pollen
(TIC), Ca/K, δ18Ocalcite, δ13Ccalcite) show clear orbital-scale cyclicity, also characterized by a
151
global ice volume minima and NHSI maxima, we observe prominent peaks in the
153
endogenic calcite) and Ca/K (a proxy for the concentration of calcite) to result from enhanced
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due to warmer conditions19. Pollen show a simultaneous increase in vegetation cover,
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particularly deciduous oaks, during early phases of interglacials. Deciduous oaks benefit from
158
suggest greater soil development, while lower δ18Ocalcite (Extended Data Fig. 3) indicate more
160
suggest higher temperatures along with maxima in annual precipitation amount and potential
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a limited length of the summer dry season21. Lower δ13Ccalcite values during these periods
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positive precipitation/evaporation (P/E) balance18. Thus, aquatic and terrestrial datasets
161
shorter summer aridity during interglacials (Extended Data Fig. 4).
163
Lake Ohrid record in a regional context, we analysed climate data time series derived from a
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To provide a better understanding of the observed precipitation variability from the
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transient 784 kyr simulation using the earth system model LOVECLIM22,23 (Extended Data
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period 1979–2017. Temperature time series of the 5°x5° Lake Ohrid grid cell simulated by
168
(Extended Data Fig. 3), such as the LR04 benthic oxygen isotope stack24 (r=–0.8737 or
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Fig. 6) as well as NOAA reanalysis precipitation data of the Lake Ohrid region for the time
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the LOVECLIM earth system model closely resemble records of first-order global ice volume
6
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r2=0.76 based on 1000-year averages of both data sets). The close match to changes in the
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amount of detrital siliciclastics and tree pollen (AP-P) confirms the sensitivity of the Lake
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highest amplitudes in precipitation time series occur during phases of reduced ice volume,
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simulated precipitation and our precipitation proxy time series (r2=0.38) and the persistence of
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response recorded at Lake Ohrid also captures changes in regional hydroclimate back to 1.36
171
Ohrid record to global-scale climate fluctuations (Fig. 2; Extended Data Figs 3 and 4). The
173
with prominent peaks during NHSI maxima. The significant positive relationship between
175
the relationship with the orbital parameters (Extended Data Fig. 4) suggest that the local
177
Ma (Fig. 2).
179
monsoon systems during precession minima and NHSI maxima is a prominent example of
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Seen both in paleo records and in climate model simulations, the intensification of NH
180
orbitally-forced changes in precipitation variability14,15,25. Iconic records of monsoon strength,
182
foraminifera oxygen isotope records14,15,27, show a positive phase relationship with Lake
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northward displacement of atmospheric circulation systems, including the position of the
186
subsidence over, and persistence of, high-pressure systems in the Mediterranean region,
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Reduced NHWI has highest impact on tropical and subtropical latitudes2 and leads to low
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Furthermore, this cooling results in a reduced meridional temperature gradient leading to a
192
relationship between the Lake Ohrid precipitation record (Fig. 2, Extended Data Figs 3 and 4)
194
region when NHWI is low.
181
such as the Chinese speleothem26, eastern Mediterranean sapropel12,13,26 and planktonic
183
Ohrid hydrological proxy time series (Fig. 2). Strengthening of NH monsoons results from a
185
Hadley cells and the ITCZ during NH summer. The shift of the Hadley cell amplifies
187
leading to warmer and drier summers17, and higher sea-surface temperatures (SST)16,28.
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latitude cooling and a southward shift of the ITCZ and the NH Hadley and Ferrel cells.
191
weakening of the westerlies based on the thermal wind relationship. The observed
193
and the monsoon archives suggests increased precipitation during the winter half-year for this
7
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The Lake Ohrid record, in combination with the transient simulation time series and
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the NOAA reanalysis data, may provide fundamental insights into the mechanisms invoked
198
last 39 years show high precipitation anomalies (defined as above two standard deviations) to
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atmospheric pattern associated with these precipitation events exhibits a trough in the Gulf of
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by orbital forcing on Mediterranean precipitation. The monthly NOAA reanalysis data of the
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occur between the months of September and December (Extended Data Fig. 7a,b). The
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Genoa region (Extended Data Fig. 7c), pointing to either increased cyclogenesis over or
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advection of North Atlantic low pressure into the western Mediterranean region.
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agreement with the reanalysis data; the model, however, underestimates the annual mean
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The annual cycle of simulated Lake Ohrid precipitation in LOVECLIM is in good
precipitation (Extended Data Fig. 8b). Maxima in our simulated precipitation time series
(defined as above two standard deviations) indicate a positive anomaly from September to
207
November (SON) in agreement with the reanalysis data (Fig. 3, Extended Data Fig. 8b).
209
both the NOAA and LOVECLIM data show pronounced troughs in the central Mediterranean
211
observations support previous modelling experiments suggesting that weakened atmospheric
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increased contrast between warm SST and lower continental air temperatures17, fuel
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at the beginning of the fall, when the stronger thermal inertia of the sea relative to the land
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in the NH atmospheric circulation cells during the winter half-year, which also favours a more
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lead to increased winter rainfall in the Mediterranean mid-latitudes.
208
Despite important differences in the geographical expansion of geopotential height anomalies,
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area and an increase of rainfall during winter half-year in our focus region (Fig. 3). Our
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stratification and reduced hemispheric temperature contrasts2, in combination with an
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precipitation increase in the Mediterranean. Such a preconditioning is particularly pronounced
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promotes local cyclogenesis17,29. Local cyclogenesis in combination with the southward shift
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southerly trajectory for storm tracks across the North Atlantic and into the Mediterranean2,
8
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Owing to the significant positive correlation between the simulation and our proxy
221
time series (Extended Data Fig. 4), in terms of timing and amplitude, we infer that this
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similar to the NH summer monsoon records, we observe a strong influence of NHSI and a
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series, suggesting persistence of the mechanism during different climate boundary conditions.
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sapropel records (Fig. 2) indicates a strong coherence of African summer monsoon strength
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mechanism primarily controlled precipitation at Lake Ohrid for the last 1.36 Myr. Indeed,
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reduced winter temperature contrast in the NH throughout the entirety of our multiproxy time
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The positive phase relationship between the Lake Ohrid precipitation proxy time series and
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and widespread Mediterranean winter half-year precipitation. Some peaks in our precipitation
proxy time series, which are not represented by sapropel layers (Fig. 2), may indicate lower
monsoon strength and reduced runoff from the African continent or that the general setting
required for sapropel deposition and preservation was not established in the Mediterranean
Sea during these periods15. During colder and drier glacial periods3 with increased global ice
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volume, lower atmospheric CO2 concentrations, and stronger mid-latitude westerlies,
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the sensitivity simulations conducted to disentangle the individual effects of orbital forcing,
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insolation forcing on precipitation appears suppressed in our record. This is in agreement with
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NH ice sheets, and CO2 on Lake Ohrid precipitation (Extended Data Fig. 6).
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also exerts a strong control on precipitation variability in the Mediterranean mid-latitudes
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well-constrained information on precipitation maxima during phases of lower
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equivalence of the past regional key drivers of precipitation extremes to those produced by
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simulation uncertainties and makes these results also relevant to predictions for the future
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Precessional forcing on insolation is not only the key driver of the NH monsoons, it
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during the Quaternary. Lake Ohrid sediment cores record highly resolved and chronologically
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intrahemispheric temperature contrast and peak SST’s over the last 1.36 Myr. The apparent
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continued anthropogenic increase of atmospheric GHG concentrations may help to reduce
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evolution of Mediterranean climate.
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30. Laskar, J. et al. A long-term numerical solution for the insolation quantities of the earth.
Astron. Astrophys. 428, 261−285 (2004). doi:10.1051/0004-6361:20041335
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340
13
341
Acknowledgments: The Hydrobiological Institute in Ohrid (S. Trajanovski and G. Kostoski)
343
logistic support for site surveys and the scientific drilling campaign. Drilling was carried out
345
Skinner provided logistic and technical advice prior and during drilling operation. The
347
project was funded by the International Continental Scientific Drilling Program (ICDP), the
349
University of Cologne, the British Geological Survey, the INGV and CNR (both Italy), and
351
tephra, which was 40Ar/39Ar dated with funding from LEFE "INTERMED" grant (CNRS-
342
and the Hydrometeorological Institute in Tirana (M. Sanxhaku and B. Lushaj) provided
344
by Drilling, Observation and Sampling of the Earth’s Continental Crust (DOSECC). A.
346
Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOPSCO) drilling
348
German Ministry of Higher Education and Research, the German Research Foundation, the
350
the governments of the republics of North Macedonia and Albania. V. Scao collected the V5
352
INSU) to S. Nomade.
354
Author Contributions: B Wagner and H Vogel designed the study and contributed equally.
356
conceived major scientific ideas of this study. A Francke (sedimentology, chronology), T
358
and L Sadori (palynology) contributed and oversaw key datasets used in the study. They
353
355
BW initiated and coordinated the SCOPSCO drilling project and drilling campaign. HV
357
Friedrich (LOVECLIM modelling), T Donders (palynology), J Lacey (isotope geochemistry),
359
360
361
362
coordinated together with F Cremer-Wagner, M Leng, E Regattieri, T Wilke and G Zanchetta
discussion and interpretations of proxy data groups and model results. Specific data were
provided by A Bertini (pollen, MIS 19–21, MIS 25–28, MIS 42–43), N Combourieu-Nebout
(pollen, MIS 1–4, MIS 8, MIS 14–15), B Giaccio (tephrostratigraphy), S Joannin (pollen,
363
MIS 1–4, MIS 13–16, MIS 30), J Just (paleomagnetic data), K Kouli (pollen, MIS 6–8, MIS
365
Koutsodendris (pollen, MIS 11–12, MIS 15), N Leicher (tephrostratigraphy), A Masi (pollen,
364
10, MIS 16–19, MIS 28–30, MIS 33), I Kousis (pollen, MIS 11–12, MIS 15), A
14
366
MIS 5–6, MIS 20–25, MIS 31–32), A M Mercuri (pollen, MIS 6, MIS 34), S Nomade
368
MIS 35–43), O Peyron (pollen, MIS 1–4, MIS 13–16, MIS 30), L Sagnotti (paleomagnetic
370
6, MIS 34). S Krastel, K Lindhorst, and T Wonik coordinated the seismic survey of Lake
372
correlation. A Grazhdani, M Melles, J Reed, and Z Levkov contributed to the conception of
374
micropaleontological and organic geochemistry data, which confirmed that the sediment
376
provided model infrastructure and resources. All authors contributed to the discussion and
377
interpretation of the data and provided comments and suggestions to the manuscript.
378
379
Author Information: Reprints and permissions information is available at
367
(tephrochronology), N Nowaczyk (paleomagnetic data), K Panagiotopoulos (pollen, MIS 7–8,
369
data), G Sinopoli (pollen, MIS 5–6), R Sulpizio (tephrostratigraphy) and P Torri (pollen MIS
371
Ohrid, the selection of the coring location and the geophysical measurements needed for core
373
the work. A Cvetkoska, J Holtvoeth, E Jovanvoska, S Tofilovska, and X Zhang provided
375
succession from the DEEP site covers the entire history of Lake Ohrid. A Timmermann
380
www.nature.com/reprints. Authors declare no competing interests. Correspondence and
381
requests for materials should be addressed to wagnerb@uni-koeln.de. Data are available in
383
https://doi.pangaea.de/10.1594/PANGAEA.896848. Data used for LOVECLIM are available
382
the main text, in the supplementary materials and in the Pangaea database at
384
at https://climatedata.ibs.re.kr/grav/data/loveclim-784k.
386
Figure legends:
388
is based on tephrostratigraphic correlation of 16 tephra layers to their radiometrically dated
385
387
Fig. 1. Chronology and location of the Lake Ohrid DEEP site record. (a) The age model
389
proximal deposits (red, first-order tie points) (b) tuning of total organic carbon (TOC) minima
390
in the DEEP site record vs. inflection points in insolation and winter season length (blue,
15
391
second-order tie points), and cross evaluation of two paleomagnetic age reversals (a; dashed
393
247 meters composite depth (mcd) of the record20 (see Methods). For the ages and errors of
395
±2,000 years. (c) The insert shows the location of Lake Ohrid and the approximate position of
397
Fig. 2. Lake Ohrid precipitation indicators and global monsoon records for the last 1.4
399
interval/oxidized sapropel, violet = ghost sapropel)12,13,27; (b) Chinese Speleostack δ18O 26 in
392
lines). The age model was calculated following the methodological approach for the upper
394
the tephra layers, see Extended Data Table 1. The tuning points (green) include an error of
396
the intertropical convergence zone (ITCZ) in summer and winter.
398
million years. (a) Eastern Mediterranean (EM) Sapropel ages (green = sapropel, red = red
400
‰ relative to VPDB; (c) Medstack δ18O planktonic28 in ‰ relative to VPDB; SST=sea-
402
relative to VPDB; (e) Lake Ohrid deciduous oaks pollen percentage; (f) Lake Ohrid total
404
between the tropic of cancer and the arctic circle30; (h) annual mean precipitation amount for
406
excluding Pinus pollen (AP-P) percentages. Tenaghi Philippon arboreal pollen (AP)
401
surface temperature, SSS=sea-surface salinity; (d) Lake Ohrid δ13C endogenic calcite in ‰
403
inorganic carbon (TIC) concentrations; (g) Northern Hemisphere winter insolation difference
405
the Lake Ohrid grid cell from the LOVECLIM simulation; (i) Lake Ohrid arboreal pollen
407
percentages3 (k) and LR04 benthic δ18O stack25 in ‰ relative to VPDB with odd numbers for
409
radiometrically dated tephra layers, blue and white diamonds the position of reversals of
411
Fig. 3. Simulated Lake Ohrid precipitation and atmospheric anomaly pattern associated
413
cell. Data based on 1,000-year averages. Dashed line indicates two standard deviations above
415
Methods for details on the model simulations. (b) Composite anomalies of September-
408
interglacials (l) are shown for comparison. Red and white diamonds indicate the position of
410
Earth’s magnetic field in the Lake Ohrid sediment record.
412
with precipitation maxima. (a) Simulated precipitation (cm yr-1) for the Lake Ohrid grid
414
the mean. Red shading highlights precipitation values exceeding two standard deviations. See
16
416
417
November (SON), 800 hPa geopotential height (m, shading) and wind (m s-1, vectors)
associated with precipitation maxima shown in (a).
418
419
420
421
422
17
423
Methods:
424
Lake and lake hydrology
426
climate zone with average monthly air temperature ranging from +26°C during summer to -
428
yr-1 with increasing altitude and occurs primarily during winter months31. The lake is ~30 km
425
Lake Ohrid (41°02’N, 20°43’E, 693 m a.s.l.; Fig. 1c) is located in the sub-Mediterranean
427
1°C during winter. Precipitation in the Lake Ohrid watershed increases from 698 to 1,194 mm
429
long, ~15 km wide, and has a maximum water depth of 293 m (Extended Data Fig. 1).
431
water input. Due to an oligotrophic state, bottom waters remain partly oxygenated for several
430
Sublacustrine karst springs (55%), direct precipitation, and river inflow (45%) constitute the
432
years, although the lake is oligomictic and a complete overturn occurs only every few years at
433
present32.
434
435
Sediment cores
437
Deep Lake Drilling System (DLDS) of Drilling, Observation and Sampling of the Earth’s
439
interdisciplinary Scientific Collaboration on Past Speciation Conditions in Lake Ohrid
441
Program (ICDP). The composite sediment record is based on 6 parallel boreholes that reached
443
99.8%. Small gaps occur between 204.719 and 204.804 mcd (8.5 cm) and between 447.89
mcd, and between 55 and 50 mcd. Subsampling in the upper 447.12 mcd excluded mass
436
Sediment cores from the Lake Ohrid DEEP site were recovered in spring 2013, using the
438
Continental Crust (DOSECC) and within the framework of the multinational and
440
(SCOPSCO) project that was co-sponsored by the International Continental Scientific Drilling
442
a terminal depth of 568 m33. Sediment recovery from 0 to 456.1 m composite depth (mcd) is
444
and 448.19 mcd (30 cm)33. Mass movement deposits (<3 cm) occur between 117 and 107
445
446
movement and tephra deposits.
447
448
Scanning-X-ray fluorescence (XRF) analysis
18
449
Scanning-XRF analysis was performed at the University of Cologne, Germany, on split core
451
Analytics) equipped with an energy dispersive silicon drift detector and a Cr-tube set to 30
453
integrated in Q-spec (Cox Analytics).
455
Elemental analysis
457
following freeze-drying and homogenization at the University of Cologne. For total carbon
459
sample material was dispersed in 10 ml deionized water. TC was determined at combustion of
461
100 and a DIMATOC 200 (DIMATEC Corp., Germany). The total organic carbon (TOC)
450
surfaces at 2.5 mm increments and 10 s dwell time using an ITRAX XRF core scanner (Cox
452
kV/30 mA. Raw data were processed and element-specific photon energy peaks were
454
456
Elemental analysis was performed on 16-cm-spaced samples (2794 samples, ~480 yr)
458
(TC) and total inorganic carbon (TIC) measurements, an aliquot of 40 mg of the homogenized
460
900°C and TIC was measured after treatment with 40% H3PO4 at 160°C using a DIMATOC
462
content was calculated as the difference between TC and TIC.
464
Fourier Transform Infrared Spectroscopy (FTIRS)
466
32 cm (1462 samples, ~1,000 yr). Measurements were performed using a Bruker Vertex 70
468
and a HTS-XT accessory unit (multisampler) in an air-conditioned laboratory at the
463
465
Relative concentration changes for quartz were assessed using FTIRS, on samples spaced at
467
equipped with a lN2-cooled MCT (mercury-cadmium-telluride) detector, a KBr beam splitter,
469
University of Bern, Switzerland. For this purpose, 11 mg of each sample and 500 mg of oven-
470
471
dried spectroscopic grade KBr (Uvasol®, Merck Corp.) were homogenized and scanned 64
times at a resolution of 4 cm-1 (reciprocal centimetres) for the wavenumber range from 3,750
472
to 520 cm-1 in diffuse reflectance mode. Data processing encompassed a linear baseline
474
zero (3,750 and 2,210–2,200 cm-1). Peak areas diagnostic for symmetric stretching of SiO4 in
473
correction to remove baseline shifts and tilts by setting two points of the recorded spectrum to
19
quartz (778 and 798 cm−1), and representative for relative abundance34,35 were integrated
475
476
using the OPUS (Bruker Corp.) software package.
477
478
Palynology processing and analysis
480
following processing, identification, and counting approaches as described in36. Dry sediment
479
Pollen analysis was carried out on sediment samples spaced at 64 cm (697 samples, ~2000 yr)
481
(1.0–1.5 g) samples were treated with cold HCl (37%vol), cold HF (40%vol), and hot NaOH
482
483
(10%vol) to dissolve carbonates, silicates, and humic acids, respectively. Glycerin-mounted
residues were analysed by transmitted light microscopy to a mean of ~533 (incl. Pinus) and
484
~250 (excl. Pinus) grains/sample. Relative abundances are based on the total terrestrial pollen
486
taxon36. Deciduous oak abundances represent the combined percentages of Quercus robur and
485
sum excl. Pinus due to overrepresentation and potential long-distance transport of this
487
Q. cerris types37, which is commonly used as an indicator for mid-elevation, relatively humid
488
forest across the Mediterranean38,39,40,41.
489
490
Isotope analysis
492
16 cm through zones of higher TIC (>0.5%), comprising a total of 1309 sediment samples.
494
sediment and oxidize reactive organic material. Potential biogenic carbonate was removed by
496
to a fine powder in an agate mortar. CO2 was evolved from 10 mg CaCO3 powders by
491
Oxygen and carbon isotopes were analysed on bulk carbonate (calcite)42 in samples spaced at
493
The samples were immersed in 5% NaClO solution for 24 h to gently disaggregate the
495
sieving and the <64 μm fraction washed with deionized water, dried at 40°C, and then ground
497
reaction with anhydrous H3PO4 overnight inside a vacuum at a constant temperature of 25°C.
498
The liberated CO2 was cryogenically purified under vacuum and collected for analysis on a
500
standard delta notation (δ18Ocalcite and δ13Ccalcite, respectively) in per mille (‰) calculated to
499
VG Optima dual inlet mass spectrometer. Oxygen and carbon isotope values are reported in
20
501
the Vienna Pee Dee Belemnite (VPDB) scale using a within-run laboratory standard (MCS)
502
503
standard was <0.1‰ (±1σ) for δ18O and δ13C.
504
505
Magnetostratigraphic analyses
507
demagnetization (10 steps up to 100 mT) was measured on ~900 discrete cube (6.3 cm3)
509
GeoForschungsZentrum, Potsdam, Germany, using a 2G Enterprises cryogenic
511
principle component analysis (PCA) after removal of low-coercivity magnetic overprints.
calibrated against international NBS standards. Analytical reproducibility for the within-run
506
Remanent magnetization in its natural state (NRM) and after step-wise alternating field
508
samples with an average 48-cm-spacing at the Paleomagnetic Laboratory at the
510
magnetometer. Paleomagnetic directions (declination and inclination) were calculated using
512
After identification of geomagnetic polarity transitions, ~500 additional samples were taken at
513
2 to 3-cm-spacing across these transitions for high-resolution analysis at the Istituto Nazionale
514
di Geofisica e Vulcanologia, Rome, Italy, using the same analytical set up and routine as in
516
overprints the primary paleomagnetic signal43, paleomagnetic transitions are faithfully
515
517
Potsdam. As glacial intervals of the core contain diagenetically formed greigite, which
preserved only in interglacial intervals, at the base of the Jaramillo sub-Chron (373.8 mcd)
518
and at the Matuyama/Brunhes (M/B) boundary (287.6 mcd).
520
Tephrostratigraphic analysis
522
mcd of the record44,45,46. Two additional tephra layers from the lower (>247 mcd) part of the
524
based on geochemical fingerprinting of single glass shards using Wavelength Dispersive
519
521
Eleven tephra and three cryptotephra layers have successfully been identified in the upper 247
523
DEEP site record are introduced here. The tephrostratigraphic correlation of these tephras is
525
Electron Microprobe Analysis (WDS-EPMA) as described in 44.
21
526
40
Ar/39Ar dating was performed at the LSCE facility (CEA, UVSQ and University
527
Paris-Saclay). V5 tephra (=OH-DP-2669 layer) was collected in Montalbano-Jonico
529
fraction 0.6-1.0 mm, were extracted from V5 and irradiated for 2 h in the Cd-lined, in-core
528
530
531
532
533
(Southern Italy, N40°17’32.8’’; E16°33’27.4’’). Twenty pristine sanidine crystals, of the
CLICIT facility of the Oregon State University TRIGA reactor (Irradiation CO 001).
Subsequently, 14 crystals were individually loaded in a copper sample holder and put into a
double vacuum Cleartran window. Each crystal was individually fused using a Synrad CO2
laser at 10-15% of nominal power (~50 W). The extracted gas was purified for 10 min by two
534
hot GP 110 and two GP 10 getters (ZrAl). Ar isotopes (36Ar, 37Ar, 38Ar, 39Ar and 40Ar) were
536
217 SEV SEN coupled to an ion counter. Neutron fluence J for each sample is calculated
538
the total decay constant of 48. J-values computed from standard grains is 0.00053220 ±
540
analytical period, and was relative to a 40Ar/36Ar ratio of 298.56 49.
542
boundaries comprising up to 500 µm large platy glass shards and minor elongated
544
position between the M/B boundary (287.6 mcd) and OH-DP-2060 (Tufo di Bagni Albula,
535
analysed by mass spectrometry using a VG5400 equipped with an electron multiplier Balzers
537
using co-irradiated Alder Creek Sanidine (ACs-2) standard with an age of 1.1891Ma 47 and
539
541
543
0.00000160. Mass discrimination was estimated by analysis of air pipette throughout the
Tephra OH-DP-2669 is a 2.5 cm thick, yellowish layer with sharp upper and lower
micropumices. Its distinct trachytic composition (Extended Data Fig. 2) and the stratigraphic
545
524.84 ka 44; Extended Data Table1) narrow potential tephrostratigraphic equivalents. Tephra
547
with a similar trachytic composition50,51 for this interval (Extended Data Fig. 2, Extended
549
majority of the SC1-35.30/SUL2-1 and OH-DP-2669 analyses correlate well with the more
551
field of the less evolved group V5a (Extended Data Fig. 2, Extended Data Table 2). Tephra
546
layer SC1-35.30/SUL2-1 from the Sulmona basin in the Italian Apennines is the only tephra
548
Data Table 2). SC1-35.30/SUL2-1 was correlated with tephra V5 from the MJS 52,53. The
550
evolved group of V5 (V5b: SiO2 >63% wt.; CaO <1.5% wt.). Only few analyses plot in the
22
552
layer SUL2-1 and V5 were 40Ar/39Ar dated at 722.8±2.4 ka50 and 719.5±12.6 ka53,
554
The previous proposed correlation of SUL2-1/V5 with the Parmenide ash found in the
556
Parmenide ash (710±5 ka) 54,55,56 and the differences in the geochemical data to OH-DP-2669
558
Tephra OH-DP-2898 is a ~0.8 cm thick, whitish-yellowish band of lenses comprising
553
respectively.
555
Crotone basin50,52 is not considered here due to a slightly younger 40Ar/39Ar age of the
557
(Extended Data Fig. 2, Extended Data Table 2).
559
fine-grained glass shards with a high degree of vesicularity and a phonolitic composition
561
indicative for interglacial conditions20. The comparison of OH-DP-2898 glass composition
560
(Extended Data Fig. 2). It is located ~2 m below the M/B boundary, in calcareous sediments
562
with those of Sulmona tephra SUL2-19, -20, -25, -29 and -31 in a similar
564
tephra close to the M7B transition, SUL2-22, -23, and -27, have a composition similar to OH-
566
(Extended Data Fig. 2, Extended Data Table 2). SUL2-27 is geochemically indistinguishable
568
geochemically indistinguishable from OH-DP-2898 and shares a similar stratigraphic position
570
OH-DP-2898 with tephra V4 from the MJS is not possible due to differences in the
572
age of 773.9±1.3 ka of V4 52, quasi-synchronous position during the 10Be peak or M/B
563
magnetostratigraphic position exclude a correlation (Extended Data Fig. 2). Other Sulmona
565
DP-2898, but SUL2-23 has slightly lower alkali and higher CaO, FeO, TiO2 concentrations
567
from OH-DP-2898, but deposited in glacial sediments of the MIS 20 57. SUL2-22 is also
569
below the M/B boundary58,59 and at the transition from MIS 20 to MIS 19 57. A correlation of
571
compositional range (Extended Data Fig. 2, Extended Data Table 2) and a younger 40Ar/39Ar
573
transition60. Also a correlation of OH-DP-2898/SUL2-22 with tephra V3 of the MJS
575
Data Fig. 2, Extended Data Table 2) and deposition of V3 during glacial conditions of MIS 20
577
climatostratigraphic position 55,61,62, but differs geochemically from OH-DP-2898/SUL2-22.
574
(801.2±19.5 ka) is excluded due to differences in the geochemical composition (Extended
576
60
. The Pitagora ash from the Crotone basin is found in a similar magneto- and
23
578
Therefore, we regard a correlation of OH-DP-2898 with SUL2-22 as most robustly and use its
579
40
581
(Extended Data Table 1). This update includes the Campanian Ignimbrite (Y-5/OH-DP-
583
from the Sulmona section64. The tephrostratigraphy of the Fucino record65 improved and
585
of TF-17, correlated to OH-DP-0624, yielded a much more precise age of 158.8 ± 3.0 ka,
580
582
Ar/39Ar age of 791.9±1.9 ka 58 for our chronology.
In addition to the new tephra correlations, we updated ages for the upper tephra layers
0169)63 and tephra layers OH-DP-0404/POP2 and OH-DP-0435/X-6, based on new results
584
reassessed the correlations established for OH-DP-0617 and OH-DP-0624 44. 40Ar/39Ar dating
586
which replaced the age of Vico B/OH-DP-0617 (162±6 ka)66.
588
provided a new chronological tie-point at 410±2 ka 67. The previously established correlation
587
589
Furthermore, the correlation of cryptotephra OH-DP-1700.6 with the Vico β eruption45
of tephra layer OH-DP-1955 with tephra layer SC-5 from the Mercure basin44 was rejected in
590
the light of its large uncertainty (±10.9 ka) and the new tephrostratigraphic data.
592
DP-2669, by updating the value of the atmospheric Ar-composition (40Ar/36Ar: 298.5 instead
594
Data Table 1) using the decay constant of 48 and an age of 1.1891 Ma for the ACs-2 flux
596
undistinguishable within uncertainty and thus used for our chronology. All other 40Ar/39Ar
597
598
ACs-2 (1.1891 Ma) and Fish Canyon sanidines (FCs) ages of 28.294 Ma.
599
600
Chronology
602
of the DEEP site sediment succession down to 447.12 mcd uses tephrochronological data44,45,
591
593
595
Reassessment of the raw Ar-isotope data of SC1-35.30/SUL2-1, the equivalent to OH-
of 295.5 originally) and removing xenocrysts58 yielded a new age of 715.02±5.4 ka (Extended
standard47. Our new 40Ar/39Ar age of V5 (716.2±5.4 ka; MSWD = 0.8, P = 0.7) is
used were recalculated using the software ArAR68 with a given decay constant and age for
601
Following the methodological approach for the upper 247 mcd of the record20, the chronology
603
46
as 1st-order tie points and tuning of climate-sensitive proxy data (TOC; ~480 yr resolution)
24
604
against orbital parameters as 2nd-order tie points considering that maxima in TIC represent
606
DEEP site since the penultimate glacial period (Y-5, X-6, P-11, and A11/12) occur at depths
608
passages in March correspond to the inflection points of increasing local summer insolation
610
equinoxes) at the latitude of Lake Ohrid (41°N; Fig. 1). Increasing summer insolation
612
organic matter (OM) supply to the sediments. An extended winter season improves lake-water
614
Thus, minima in TOC result from moderate OM supply to the sediments and improved
616
resolution in the DEEP site record used for tuning purposes.
618
cryptotephra layers and 66 2nd-order tie points obtained from orbital tuning were cross
605
607
609
interglacial periods19,20. Some chronologically well-constrained tephra layers deposited at the
where TOC shows minima at times of the perihelion passage in March20. These perihelion
(21st June) and winter-season length (number of days between the September and March
611
promotes high summer temperatures, primary productivity in the water column and increases
613
mixing which enhances oxidation of OM in the water column and the surface sediments20.
615
oxidation of OM at the sediment surface and are due to their available high temporal
617
The independent chronological information obtained from the 16 tephra and
619
evaluated by the two paleomagnetic age constraints (base of the Jaramillo sub-Chron and
621
considering overall uniform (mem.strength=60, mem.mean=0.9, thick=80 cm) sedimentation
620
Matuyama/Brunhes M/B; Fig. 1). The age model was calculated using Bacon 2.2 69,
622
rates (acc.shape=1.5, acc. mean=20) at the DEEP site33. An error of ±2,000 years was applied
623
to the 2nd-order tie points to account for tuning inaccuracy. The 95% confidence intervals of
624
ages for specific depths produced by the Bacon Bayesian age modelling average at ±5,500
626
447.12 m of the DEEP site record covers the last 1.364 Myr, continuously.
628
Cave speleothem record70 and found agreement within errors of the chronologies. Arboreal
625
627
years with a maximum of ±10,680 years. The resulting chronology implies that the upper
We20 evaluated the DEEP site’s chronology against the 0-160 ka U/Th dated Soreq
25
629
pollen (AP) percentages in the DEEP site record are also in agreement with those from the
630
orbitally-tuned Tenaghi Philippon record3 back to 1.364 Ma (Fig. 2).
632
Model simulations and forcing
634
impacts of orbital forcing, Northern Hemisphere (NH) ice sheets, and variations in
631
633
Transient simulations with the Earth system model LOVECLIM were conducted to study the
635
atmospheric greenhouse gases (GHGs) on glacial-interglacial climate change.
637
atmospheric component of LOVECLIM is the spectral T21, three-level model ECBilt72 based
639
ice component of LOVECLIM consists of a free-surface Ocean General Circulation Model
641
Atmosphere and ocean components are coupled through the exchange of freshwater and heat
636
LOVECLIM is a coupled ocean-atmosphere-sea ice-vegetation model71. The
638
on quasi-geostrophic equations extended by estimates of ageostrophic terms. The ocean-sea
640
with a 3°x3° horizontal resolution coupled to a dynamic-thermodynamic sea-ice model73.
642
fluxes. The vegetation model VECODE74 computes the evolution of terrestrial vegetation
644
The transient simulations of the last 784,000 years were forced by time-dependent
643
cover based on annual mean surface temperature and precipitation.
645
boundary conditions for orbital parameters, atmospheric GHG concentrations, NH ice sheet
647
calculated according to76. Atmospheric GHG concentrations were prescribed according to
646
orography, and albedo following the methodology described in75. The orbital forcing was
648
reconstructions from EPICA Dome C for CO277 as well as CH4 and N2O78. Orbital forcing and
649
atmospheric GHG concentrations were updated every model year. The effects of NH ice
651
with an acceleration factor of 5, which compresses 784,000 forcing years into 156,000 model
653
model simulation is an updated version of the one presented in75 and uses a higher climate
650
652
sheets on albedo and land topography were prescribed according to79. The forcing was applied
years. This acceleration factor is appropriate for quickly equilibrating surface variables. The
26
654
sensitivity resulting in a better representation of the glacial-interglacial surface temperature
655
amplitude23.
657
described above (Extended Data Fig. 6). The sensitivity simulations cover the last four glacial
659
ice sheets and orbital parameters to glacial-interglacial climate change. The first sensitivity
661
atmospheric GHG concentrations. The “GHG effect” can then be calculated as the difference
663
simulation uses transient forcing as described above but constant PI NH ice sheets (extent and
665
simulation and this simulation. Two simulations were designed to study the role of orbital
667
used. However, one simulation was run under constant PI atmospheric CO2 concentration of
656
Four sensitivity simulations were conducted in addition to the full-forcing simulation
658
cycles (408,000 years) and aim at exploring the individual effects of atmospheric GHGs, NH
660
simulation uses transient forcing as described above but constant preindustrial (PI)
662
between the simulation using the full forcing and this simulation. The second sensitivity
664
albedo). The “NH ice sheet effect” is calculated as the difference between the full-forcing
666
forcing under warm and cold climate. For both simulations, transient orbital parameters are
668
280 ppm, whereas the second simulation uses a constant atmospheric CO2 concentration of
669
200 ppm resulting in a colder background climate.
671
Data analysis
673
deciduous oak pollen percentage data, a wavelet power spectrum was computed for the
675
interpolation) at 0.3 kyr (TIC) and 1.0 kyr (pollen), and subsequently submitted to continuous
677
approach by 81. Results of the CWT show persistent presence of 100 kyr and ~21 kyr orbital
670
672
To assess the temporal evolution of dominant periodicities in the DEEP site TIC and
674
respective time series. The time series were resampled at regular intervals (linear
676
wavelet transform (CWT, Morlet window) using PAST v.3.21 software80 following the
678
frequencies, and a clear presence of 41 kyr in the early half of the pollen record. Relative to
27
679
the pollen, the CWT results of the TIC show a more pronounced 100 kyr cyclicity over the
680
entire record, and less pronounced 21 kyr signals.
682
maxima against precession forcing, the bandpass-filtered 18–25 kyr component of the proxy
684
Partial least squares regression (PLSR) was used to test the correlation of TIC and
681
To quantitatively test the observed correlation between deciduous oak and TIC
683
data was regressed against precession based on the La2004 orbital solution30.
685
deciduous oaks as predictive variables with LOVECLIM temperature and precipitation output
687
filtered using a frequency centred at 0.05 and a bandwidth of 0.02 prior to multivariate
686
data. PLSR was performed using SIMCA 14 (Sartorius Stedim Biotech). All datasets were
688
statistical analysis to accommodate for slight age offsets between proxy and simulation data.
690
Methods and Extended Data files references:
689
691
31. Popovska, C. & Bonacci, O. Basic data on the hydrology of Lakes Ohrid and Prespa.
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33. Wagner, B. et al. The SCOPSCO drilling project recovers more than 1.2 million years of
698
34. Farmer, V. C. The infrared spectra of minerals, edited by: V. C. Farmer, Mineralogical
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35. Chukanov, N. V. Infrared Spectra of Mineral Species. Springer, Dordrecht, Heidelberg,
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705
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877
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Data Availability
881
database at https://doi.pangaea.de/10.1594/PANGAEA.896848. Data used for LOVECLIM
880
Data are available in the main text, in the supplementary materials and in the Pangaea
882
are available at https://climatedata.ibs.re.kr/grav/data/loveclim-784k.
884
Code Availability
886
the IBS Center for Climate Physics: https://climatedata.ibs.re.kr/grav/data/loveclim-784k.
883
885
Model data produced by the LOVECLIM simulations are available through the data centre of
887
Additional data are available upon request made to Tobias Friedrich (tobiasf@hawaii.edu).
889
Extended Data Legends
888
36
890
Extended Data Figure 1 | Map of Lake Ohrid and its surrounding area. Geology,
891
topography, and bathymetry compiled from19,82 and geological maps of Albania and North
893
of 293 m. The water depth at the DEEP drill site is 240 m.
895
Extended Data Figure 2 | Correlation of tephra layers at the DEEP site with tephra
897
Al2O3, (c) CaO vs. TiO2, (d) Na2O vs. K2O, and (e) total alkali vs. silica (TAS) diagram86
892
894
Macedonia. The lake is located at an altitude of 693 m a.s.l. and has a maximum water depth
896
layers found in mid-distal records. Bi-oxide plots of (a) CaO vs. FeOtotal, (b) CaO vs.
898
show the correlation of OH-DP-2669 with the tephra layers SC1-35.30/SUL2-1/V5 and the
900
CaO vs. TiO2, (i) Na2O vs. K2O, and (k) TAS diagram show the correlation of OH-DP-2898
Error bars of the Parmenide Ash refer to 54.Tephra ages, geochemical data, tephrostratigraphic
899
differences to the Parmenide ash. Bi-oxide plots of (f) CaO vs. FeOtotal, (g) CaO vs. Al2O3, (h)
901
with tephra SUL2-22 and the differences to SUL2-23, -27, -31, V4, V3, and the Pitagora ash.
902
903
discussion and references are provided in Extended Data Tables 1 and 2 and in Methods.
904
905
Extended Data Figure 3 | Lake Ohrid LOVECLIM simulation data and sedimentary
907
for the Lake Ohrid grid cell from the LOVECLIM simulation; (b) simulated precipitation
909
organic carbon (TOC) concentrations; (d) Lake Ohrid δ13C endogenic calcite in ‰ relative to
911
sedimentary quartz content; (g) Lake Ohrid K intensities in kilo counts and displayed using a
913
mean; (i) Lake Ohrid Ca intensities in kilo counts and displayed using a 11 pt running mean;
906
paleoclimate and paleoenvironment proxies. (a) Simulated surface-air temperature (SAT)
908
amount for the Lake Ohrid grid cell from the LOVECLIM simulation; (c) Lake Ohrid total
910
VPDB; (e) Lake Ohrid δ18O endogenic calcite in ‰ relative to VPDB; (f) Lake Ohrid relative
912
914
915
11pt running mean; (h) Lake Ohrid ratio of Ca/K intensities displayed using a 11 pt running
(k) Lake Ohrid total inorganic carbon (TIC) concentrations; (l) Lake Ohrid deciduous oaks
pollen percentages; (m) Lake Ohrid arboreal pollen excluding Pinus pollen (AP-P)
37
916
percentages; red and white diamonds indicate the position of radiometrically dated tephra
918
Ohrid sediment record. (b), (d), (e), (K), (l) and (m) are from Fig. 2.
920
Extended Data Figure 4 | Data analysis. Continuous wavelet transform results for
922
Ohrid DEEP where colour represents the signal amplitude at a given time and spectral period
924
test according to 81) against a red-noise background spectrum with autocorrelation coefficient
926
in PAST (80 based on 83). Thick grey line indicates the “cone of influence” outside of which
928
pass-filtered 18-25 ky component of (c) % TIC and (d) the % deciduous oak against
917
919
layers, blue and white diamonds the position of reversals of Earth’s magnetic field in the Lake
921
percentages of total inorganic carbon (TIC; a) and deciduous oak pollen (b) time series from
923
(yellow highest, red lowest power). Black contour is the 5% significance level (chi-squared
925
of 0.95, estimated through an autoregressive–moving-average (ARMA) model implemented
927
boundary effects can influence the results. Least squares regression (red line) between band
929
precession at 1 ky resolution. Blue lines indicate 95% bootstrapped (n=1999) confidence
931
response (steeper slope) of the deciduous oaks. Partial least squares regression (PLSR) using
933
precipitation output data as observations. PLSR was performed using SIMCA 14 (Sartorius
935
of 0.02 prior to multivariate statistical analysis to accommodate for slight offsets in age
937
correlations of simulated temperatures (e) and of simulated precipitation (f) data to proxy
939
compared to temperature.
930
intervals. Results show significant negative relationships for both proxies, with a stronger
932
TIC and deciduous oaks as predictive variables and LOVECLIM (e) temperature and (f)
934
Stedim Biotech). All datasets were filtered using a frequency centred at 0.05 and a bandwidth
936
differences between proxy and simulation data. Results show highly significant positive
938
data, with a higher sensitivity of TIC and deciduous oaks towards changes in precipitation
940
38
941
Extended Data Figure 5 | Lake Ohrid precipitation indicators and global monsoon
943
based on Soreq Cave speleothem δ18O data and U/Th chronology84; (b) simulated
945
Ohrid deciduous oaks pollen percentage; (d) Lake Ohrid total inorganic carbon (TIC)
942
944
records during MIS 5. (a) Ages of sapropels and humid phases in the Eastern Mediterranean
precipitation amount for the Lake Ohrid grid cell from the LOVECLIM simulation; (c) Lake
946
concentrations; (e) Chinese Speleostack δ18O 25 in ‰ relative to VPDB; red and white
948
record. The chronology of the MIS 5 interval in the Lake Ohrid DEEP site record is based on
947
diamonds indicate the position of radiometrically dated tephra layers in the Lake Ohrid
949
85
951
Extended Data Figure 6 | Simulated Lake Ohrid precipitation for full-forcing run and
953
(black) and a simulation using only orbital forcing under a warm background climate (red).
955
climate (blue). (c) Black line as in (a) and a simulation using full-forcing except for a constant
950
.
952
sensitivity simulations. (a) Lake Ohrid precipitation (cm yr-1) for full-forcing simulation
954
(b) Black line as in (a) and a simulation using only orbital forcing under a cold background
956
preindustrial NH ice sheet. (d) Black line as in (a) and a simulation using full-forcing except
958
only cover the last 408 kyr. Please see Methods for details on the sensitivity simulations.
960
Extended Data Figure 7 | NOAA reanalysis data for the Mediterranean region. (a)
962
monthly means. Dashed line indicates two standard deviations above the mean. (b) Composite
964
maxima shown in (a) and referring to the months shown in (c). (c) Monthly distribution of
957
959
961
for constant preindustrial GHG concentrations. Please note that the sensitivity simulations
Reconstructed precipitation (cm yr-1) for the Lake Ohrid reanalysis grid cell. Data based on
963
anomalies of 850 hPa geopotential height (m) associated with Lake Ohrid precipitation
965
precipitation maxima shown in (a).
966
39
967
Extended Data Figure 8 |. Mean seasonal cycle of Lake Ohrid precipitation - model
969
precipitation (cm yr-1) for all model years (green) and model years with annual-mean
968
simulation and NOAA reanalysis data. (a) Mean seasonal cycle of simulated Lake Ohrid
970
precipitation exceeding two standard deviations (magenta). Please see also Fig. 3a. (b) Mean
(blue) and simulated for the 1–0 kyr period (red). The annual means were removed for better
971
seasonal cycle of Lake Ohrid precipitation (cm yr-1) derived from NOAA reanalysis data
972
973
comparison and are provided in the panel.
974
975
Extended Data Table 1 | Selected tephra layers from Lake Ohrid and their correlation
976
with tephra layers of other records. 40Ar/39Ar ages from literature were recalculated using a
978
(FCs) at 28.294 Ma73. Tephra ages in bold are used for age-depth modelling in Fig. 1. Age
979
uncertainties are provided according to the original reference (Reference age).
980
981
Extended Data Table 2 | Average compositions of OH-DP-2669 and OH-DP-2898 and
983
SC1-35.50 from 50; V5, V4, V3, Pitagora ash from 52 and the Parmenide ash from 54. x̅ =
977
982
984
decay constant73 and Alder Creek sanidine (ACs-2) at 1.1891 Ma74 or Fish Canyon sanidine
potential equivalent correlations. Data of SUL2-1, SUL2-22, SUL2-23, SUL2-27 from 51;
mean; S = standard deviation; n= number of analysis.
985
40
986
987
Fig. 1
988
989
41
Fig. 2
EM
Sapropels
a
Speleostack
b
-10
+
SE Asian
monsoon strength
-
-8
-6
δ13Ccalcite (VPDB ‰)
0
2
2
L. Ohrid
-2
c
d
0
20
0
+
temp./
karst
runoff
-
TIC (%wt)
L. Ohrid
8
4
f
insolation
difference
g
260
LOVECLIM
270
30
+
simulated
precipitation
-
h
20
100
60
40
0
100
k
5
1
l
4
50
7
9
11
13
15
17
19
23
3
27
0
31
25
21
29
33
35
37
39 41
43
45
5
0
200
400
600
Age (ka)
42
800
1,000
1,200
1,400
AP (%)
LR04
20
T. Philippon
δ18Obenthic (VPDB ‰)
+
tree
cover
-
L. Ohrid
80
i
AP-Pinus (%)
precipitation (cm yr-1)
higher
N. Hemisphere
winter insol.
250
Tropics - Arctic (W m-2)
0
lower
L. Ohrid
40
e
deciduous oaks (%)
60
+
soil
moisture
-
992
993
994
Medstack
+(-)
SST
(SSS)
-(+)
δ18Oplanktonic (VPDB ‰)
δ18O(VPDB ‰)
990
991
ice
volume
+
Fig. 3
Lake Ohrid
annual-mean
precipitation (cm yr -1)
995
996
40.0
36.0
32.0
28.0
24.0
20.0
16.0
(a)
100
0
200
300
400
Age (ka)
500
700
600
60°N
(b)
50°N
11
40°N
2
30°N
20°N
-7
-16
1 m s-1
GPH-anomaly and wind-anomaly (800 hPa, SON) for precipitation above 2xSTD
10°N
997
20
30°W
15°W
0°
15°E
43
30°E
45°E
60°E
-25
m