Eight tree-ring chronologies from coastal sites along the Gulf of Alaska (GOA) are used to develo... more Eight tree-ring chronologies from coastal sites along the Gulf of Alaska (GOA) are used to develop a 227-year (1762–1988) reconstruction of spring/summer (March–September) coastal land temperatures for the region. This reconstruction explains 35% of the variance in the instrumental temperature data. The tree-ring records and reconstruction reflect the documented 1976 transition from cold to warm conditions in the North Pacific
Decadal-scale oscillatory modes of atmosphere-ocean variability have recently been identified in ... more Decadal-scale oscillatory modes of atmosphere-ocean variability have recently been identified in instrumental studies of the Pacific sector. The regime shift around 1976 is one example of such a fluctuation, which has been shown to have significantly impacted climate and the environment along the western Americas. The length of meteorological data for the Pacific and western Americas critically limits analyses of such decadal-scale climate variability. Here we present reconstructions of the annual Pacific Decadal Oscillation (PDO) index based on western North American tree-ring records which account for up to 53% of the instrumental variance and extend as far back as AD 1700. The PDO reconstructions indicate that decadal-scale climatic shifts have occurred prior to the period of instrumental record. Evaluation of temperature and precipitation-sensitive tree-ring series from the northeast Pacific as well as these reconstructions reveals evidence for a shift towards less pronounced interdecadal variability after about the middle 1800s. Our analyses also suggest that sites from both the northeast Pacific coast as well as the subtropical Americas need to be included in proxy data sets used to reconstruct the PDO.
Tree ring, ice core and glacial geologic histories for the past several centuries offer an opport... more Tree ring, ice core and glacial geologic histories for the past several centuries offer an opportunity to characterize climate variability and to identify the key climate parameters forcing glacier expansion in Kamchatka over the past 400 years. A newly developed larch ring-width chronology (AD 1632-2004) is presented that is sensitive to past summer temperature variability. Individual low growth years in the larch record are associated with several known and proposed volcanic events from the Northern Hemisphere. The comparison of ring width minima and those of Melt Feature Index of Ushkovsky ice core helps confirm a 1-3 year dating accuracy~for this ice core series over the late 18th to 20th centuries. Decadal variations of low summer temperatures (tree-ring record) and high annual precipitation (ice core record) are broadly consistent with intervals of positive mass balances measured and estimated at several glaciers in 20th century, and with moraine building. According to the tree-ring data the 1860s-1880s were the longest coldest interval in the last 350 years. The latest part of this period (1880s) coincided with the positive anomaly in accumulation. This coincidence led to a positive mass balance, which is most likely responsible for glacier advances and moraine deposition of the end of 19th-early 20th centuries. As well as in some other high latitude regions (Spitsbergen, Polar Urals, Franz Jozef Land etc.) in Kamchatka these advances marked the last millennium glacial maximum. In full agreement with subsequent summer warming trend, inferred both from instrumental and tree ring data, glacier advances since 1880s have been less extensive. The late 18th century glacier expansion coincides with the inferred summer temperature decrease recorded by the ring width chronology. However, both the advance and the summer temperature decrease were less prominent that in the end of 19th century. Comparisons of the glacier history in Kamchatka with records from Alaska and the Canadian Rockies suggests broadly consistent intervals of glacier expansion and inferred summer cooling during solar irradiance minima.
The Maunder Minimum interval (from the mid-1600s-early 1700s) is believed to have been one of the... more The Maunder Minimum interval (from the mid-1600s-early 1700s) is believed to have been one of the coldest periods of the past thousand years in the Northern Hemisphere. A maximum latewood density temperature reconstruction for the Wrangell Mountains, southern Alaska (1593-1992) provides information on regional temperature change during the Maunder Minimum and other periods of severe cold over the past four centuries. The Wrangell density record, which reflects warm season (July-September) temperatures, shows an overall cooling over the Maunder Minimum period with annual values reaching as low as -1.8oC below the long-term mean. Ring widths, which can integrate annual as well as summer conditions, also show pronounced cooling at the Wrangell site during this time, as do Arctic and hemispheric-scale temperature reconstructions based on tree rings and other proxy data. Maximum ages of glacial advance based on kill dates from overrun logs (which reflect cooler temperatures) coincide temporally with the cooling seen in the density and ring width records. In contrast, a recent modeling study indicates that during this period there was cold season (November-April) warming over much of Alaska, but cooling over other northern continental regions, as a result of decreased solar irradiance initiating low Arctic Oscillation index conditions. The influence of other forcings on Alaskan climate, the absence of ocean dynamical feedbacks in the model, and the different seasonality represented by the model and the trees may be some of the possible explanations for the different model and proxy results.
ABSTRACT A top priority in climate research is obtaining broad-extent and long-term data to suppo... more ABSTRACT A top priority in climate research is obtaining broad-extent and long-term data to support analyses of historical patterns and trends, and for model development and evaluation. Along with directly measured climate data from the present and recent past, it is important to obtain estimates of long past climate variations spanning multiple centuries and millennia. Dendroclimatic Studies at the North American Tree Line presents an overview of the current state of dendroclimatology, its contributions over the past few decades, and its future potential. The material included is not useful not only to those who generate tree-ring records of past climate-dendroclimatologists, but also to users of their results-climatologists, hydrologists, ecologists and archeologists. In summary, this book: Sheds light on recent and future climate trends by assessing long term past climatic variations from tree rings Is a timely coverage of a crucial topic in climate science portraying recent warming trends which are of serious concern today Features well-reputed scientists highlighting new advanced methodologies to reconstruct past climate change Models the tree growth environmental response
ABSTRACT A new ring-width record from the eastern flanks of the Eastern Sakhalin Range, Sakhalin ... more ABSTRACT A new ring-width record from the eastern flanks of the Eastern Sakhalin Range, Sakhalin Island, Russian Federation is significantly correlated with summer temperatures and allows for the reconstruction of May–July average temperatures for the past 400 years. The reconstruction explains 37 % of the variance in May–July temperatures and shows a strong cooling between 1680 and 1710 CE coincident with the Maunder solar minimum and in agreement with other independent tree-ring reconstructions and glacier histories from sites along the margin of the Sea of Okhotsk. While recent decades are among the warmest in the record they are rivaled by periods centered on 1650 and 1850 CE. Warming in the observational record and the reconstruction is consistent with the influence of the declining strength of the Siberian High and loss of sea ice over the same interval. Decadal (17–25 year) variability persists throughout the reconstruction. At interannual timescales the Sakhalin reconstruction is most strongly correlated with local and central North Pacific sea surface temperatures over the past 120 years, whereas at decadal timescales there is an additional association with Asian land surface temperatures.
Many paleoclimate and landscape change studies in the American Midwest have focused on the Late G... more Many paleoclimate and landscape change studies in the American Midwest have focused on the Late Glacial and early Holocene time periods (~16–11ka), but little work has addressed landscape change in this area between the Last Glacial Maximum and the Late Glacial (~22–16ka). Sediment cores were collected from 29 new lake and bog sites in Ohio and Indiana to address this
ABSTRACT Glacier mass-balance reconstructions provide a means of placing relatively short observa... more ABSTRACT Glacier mass-balance reconstructions provide a means of placing relatively short observational records into a longer-term context. In western North America, mass-balance records span four to five decades and capture a relatively narrow window of glacial behavior over an interval that was dominated by warming and ablation. We use temperature- and moisture-sensitive tree-ring series to reconstruct annual mass balance for six glaciers in the Pacific Northwest and Alaska. Mass-balance models rely on the climatic sensitivity of tree-ring chronologies and teleconnection patterns in the North Pacific. The reconstructions extend through the mid to latter portions of the Little Ice Age (LIA) and explore the role of climate variability in forcing mass balance across multiple environmental gradients. Synchronous positive mass-balance intervals coincide with regional moraine building and solar minima, whereas differences in LIA glacier behavior are related to synoptic climate forcing. Secular warming in the late 19th century to present corresponds with the only multi-decadal intervals of negative mass balance in all glacier reconstructions. This suggests that contemporary retreat in western North America is unique with respect to the last several centuries and that regional patterns of glacier variability are now dominated by global climate forcing.
Eight tree-ring chronologies from coastal sites along the Gulf of Alaska (GOA) are used to develo... more Eight tree-ring chronologies from coastal sites along the Gulf of Alaska (GOA) are used to develop a 227-year (1762–1988) reconstruction of spring/summer (March–September) coastal land temperatures for the region. This reconstruction explains 35% of the variance in the instrumental temperature data. The tree-ring records and reconstruction reflect the documented 1976 transition from cold to warm conditions in the North Pacific
Decadal-scale oscillatory modes of atmosphere-ocean variability have recently been identified in ... more Decadal-scale oscillatory modes of atmosphere-ocean variability have recently been identified in instrumental studies of the Pacific sector. The regime shift around 1976 is one example of such a fluctuation, which has been shown to have significantly impacted climate and the environment along the western Americas. The length of meteorological data for the Pacific and western Americas critically limits analyses of such decadal-scale climate variability. Here we present reconstructions of the annual Pacific Decadal Oscillation (PDO) index based on western North American tree-ring records which account for up to 53% of the instrumental variance and extend as far back as AD 1700. The PDO reconstructions indicate that decadal-scale climatic shifts have occurred prior to the period of instrumental record. Evaluation of temperature and precipitation-sensitive tree-ring series from the northeast Pacific as well as these reconstructions reveals evidence for a shift towards less pronounced interdecadal variability after about the middle 1800s. Our analyses also suggest that sites from both the northeast Pacific coast as well as the subtropical Americas need to be included in proxy data sets used to reconstruct the PDO.
Tree ring, ice core and glacial geologic histories for the past several centuries offer an opport... more Tree ring, ice core and glacial geologic histories for the past several centuries offer an opportunity to characterize climate variability and to identify the key climate parameters forcing glacier expansion in Kamchatka over the past 400 years. A newly developed larch ring-width chronology (AD 1632-2004) is presented that is sensitive to past summer temperature variability. Individual low growth years in the larch record are associated with several known and proposed volcanic events from the Northern Hemisphere. The comparison of ring width minima and those of Melt Feature Index of Ushkovsky ice core helps confirm a 1-3 year dating accuracy~for this ice core series over the late 18th to 20th centuries. Decadal variations of low summer temperatures (tree-ring record) and high annual precipitation (ice core record) are broadly consistent with intervals of positive mass balances measured and estimated at several glaciers in 20th century, and with moraine building. According to the tree-ring data the 1860s-1880s were the longest coldest interval in the last 350 years. The latest part of this period (1880s) coincided with the positive anomaly in accumulation. This coincidence led to a positive mass balance, which is most likely responsible for glacier advances and moraine deposition of the end of 19th-early 20th centuries. As well as in some other high latitude regions (Spitsbergen, Polar Urals, Franz Jozef Land etc.) in Kamchatka these advances marked the last millennium glacial maximum. In full agreement with subsequent summer warming trend, inferred both from instrumental and tree ring data, glacier advances since 1880s have been less extensive. The late 18th century glacier expansion coincides with the inferred summer temperature decrease recorded by the ring width chronology. However, both the advance and the summer temperature decrease were less prominent that in the end of 19th century. Comparisons of the glacier history in Kamchatka with records from Alaska and the Canadian Rockies suggests broadly consistent intervals of glacier expansion and inferred summer cooling during solar irradiance minima.
The Maunder Minimum interval (from the mid-1600s-early 1700s) is believed to have been one of the... more The Maunder Minimum interval (from the mid-1600s-early 1700s) is believed to have been one of the coldest periods of the past thousand years in the Northern Hemisphere. A maximum latewood density temperature reconstruction for the Wrangell Mountains, southern Alaska (1593-1992) provides information on regional temperature change during the Maunder Minimum and other periods of severe cold over the past four centuries. The Wrangell density record, which reflects warm season (July-September) temperatures, shows an overall cooling over the Maunder Minimum period with annual values reaching as low as -1.8oC below the long-term mean. Ring widths, which can integrate annual as well as summer conditions, also show pronounced cooling at the Wrangell site during this time, as do Arctic and hemispheric-scale temperature reconstructions based on tree rings and other proxy data. Maximum ages of glacial advance based on kill dates from overrun logs (which reflect cooler temperatures) coincide temporally with the cooling seen in the density and ring width records. In contrast, a recent modeling study indicates that during this period there was cold season (November-April) warming over much of Alaska, but cooling over other northern continental regions, as a result of decreased solar irradiance initiating low Arctic Oscillation index conditions. The influence of other forcings on Alaskan climate, the absence of ocean dynamical feedbacks in the model, and the different seasonality represented by the model and the trees may be some of the possible explanations for the different model and proxy results.
ABSTRACT A top priority in climate research is obtaining broad-extent and long-term data to suppo... more ABSTRACT A top priority in climate research is obtaining broad-extent and long-term data to support analyses of historical patterns and trends, and for model development and evaluation. Along with directly measured climate data from the present and recent past, it is important to obtain estimates of long past climate variations spanning multiple centuries and millennia. Dendroclimatic Studies at the North American Tree Line presents an overview of the current state of dendroclimatology, its contributions over the past few decades, and its future potential. The material included is not useful not only to those who generate tree-ring records of past climate-dendroclimatologists, but also to users of their results-climatologists, hydrologists, ecologists and archeologists. In summary, this book: Sheds light on recent and future climate trends by assessing long term past climatic variations from tree rings Is a timely coverage of a crucial topic in climate science portraying recent warming trends which are of serious concern today Features well-reputed scientists highlighting new advanced methodologies to reconstruct past climate change Models the tree growth environmental response
ABSTRACT A new ring-width record from the eastern flanks of the Eastern Sakhalin Range, Sakhalin ... more ABSTRACT A new ring-width record from the eastern flanks of the Eastern Sakhalin Range, Sakhalin Island, Russian Federation is significantly correlated with summer temperatures and allows for the reconstruction of May–July average temperatures for the past 400 years. The reconstruction explains 37 % of the variance in May–July temperatures and shows a strong cooling between 1680 and 1710 CE coincident with the Maunder solar minimum and in agreement with other independent tree-ring reconstructions and glacier histories from sites along the margin of the Sea of Okhotsk. While recent decades are among the warmest in the record they are rivaled by periods centered on 1650 and 1850 CE. Warming in the observational record and the reconstruction is consistent with the influence of the declining strength of the Siberian High and loss of sea ice over the same interval. Decadal (17–25 year) variability persists throughout the reconstruction. At interannual timescales the Sakhalin reconstruction is most strongly correlated with local and central North Pacific sea surface temperatures over the past 120 years, whereas at decadal timescales there is an additional association with Asian land surface temperatures.
Many paleoclimate and landscape change studies in the American Midwest have focused on the Late G... more Many paleoclimate and landscape change studies in the American Midwest have focused on the Late Glacial and early Holocene time periods (~16–11ka), but little work has addressed landscape change in this area between the Last Glacial Maximum and the Late Glacial (~22–16ka). Sediment cores were collected from 29 new lake and bog sites in Ohio and Indiana to address this
ABSTRACT Glacier mass-balance reconstructions provide a means of placing relatively short observa... more ABSTRACT Glacier mass-balance reconstructions provide a means of placing relatively short observational records into a longer-term context. In western North America, mass-balance records span four to five decades and capture a relatively narrow window of glacial behavior over an interval that was dominated by warming and ablation. We use temperature- and moisture-sensitive tree-ring series to reconstruct annual mass balance for six glaciers in the Pacific Northwest and Alaska. Mass-balance models rely on the climatic sensitivity of tree-ring chronologies and teleconnection patterns in the North Pacific. The reconstructions extend through the mid to latter portions of the Little Ice Age (LIA) and explore the role of climate variability in forcing mass balance across multiple environmental gradients. Synchronous positive mass-balance intervals coincide with regional moraine building and solar minima, whereas differences in LIA glacier behavior are related to synoptic climate forcing. Secular warming in the late 19th century to present corresponds with the only multi-decadal intervals of negative mass balance in all glacier reconstructions. This suggests that contemporary retreat in western North America is unique with respect to the last several centuries and that regional patterns of glacier variability are now dominated by global climate forcing.
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