We present a new measurement of air shower muons made during atmospheric ascent of the High Energ... more We present a new measurement of air shower muons made during atmospheric ascent of the High Energy Antimatter Telescope balloon experiment. The muon charge ratio mu+ / mu- is presented as a function of atmospheric depth in the momentum interval 0.3-0.9 GeV/c. The differential mu- momentum spectra are presented between 0.3 and about 50 GeV/c at atmospheric depths between 13 and 960 g/cm^2. We compare our measurements with other recent data and with Monte Carlo calculations of the same type as those used in predicting atmospheric neutrino fluxes. We find that our measured mu- fluxes are smaller than the predictions by as much as 70% at shallow atmospheric depths, by about 20% at the depth of shower maximum, and are in good agreement with the predictions at greater depths. We explore the consequences of this on the question of atmospheric neutrino production.
Recent trends and changes in the observed river discharge into Hudson, James, and Ungava Bays (HJ... more Recent trends and changes in the observed river discharge into Hudson, James, and Ungava Bays (HJUBs) for the period 1964-1994 will be presented. Forty-two rivers with outlets into these bays contribute on average 700 cubic kilometers (= 0.02 sverdrups) of freshwater to the Arctic Ocean. River discharge attains a mean annual peak of 4.2 cubic kilometers per day on average each 17 June for the system as a whole, whereas the minimum of 0.6 cubic kilometers occurs on average each 3 April. The Nelson River supplies as much as 30% of the daily discharge for the entire system during winter, but diminishes in relative importance during spring and summer. Runoff rates per contributing area are highest (lowest) on the eastern (western) shores of Hudson and James Bays. Linear trend analyses reveal decreasing discharge in 38 out of the 42 rivers over the 31-year period. By 1994, the total annual freshwater discharge into the Arctic Ocean diminished by 110 cubic kilometers from its values in 1964, equivalent to a reduction of 0.0035 sverdrups. The annual peak discharge rates associated with snowmelt advanced by 16 days between 1964 and 1994 and has diminished slightly in intensity. There is a direct correlation between the time of this hydrological event and the latitude of a river's mouth; the timing of the peak discharge rates varies by 5 days for each degree of latitude. Continental snowmelt induces a seasonal pulse of freshwater from HJUBs that is tracked along its path into the Labrador Current and that coincides with ocean salinity anomalies on the inner Newfoundland Shelf. The talk will end with a discussion on the implications of a changing freshwater regime in HJUBs.
Trends and variability in the 1964-2007 annual streamflow for 45 rivers spanning 5.2 × 106 km2 of... more Trends and variability in the 1964-2007 annual streamflow for 45 rivers spanning 5.2 × 106 km2 of northern Canada are investigated. Discharge averages 1153 km3 yr-1 with a standard deviation of 71.4 km3 yr-1 and coefficient of variation (CVQ) of 6.2% over the 44-year period. A trend analysis reveals a recent (1989-2007) 15.5% increase in the annual flows owing to much-above average values recorded over the past decade. Trends in CVQ computed from 11-year moving windows of annual streamflows exhibit spatially coherent signals with increasing variability across most of northern Canada, excluding some rivers with outlets to the Labrador Sea and eastern James Bay. For the period of interest, 46% and 30% of the available gauged area and river discharge, respectively, experienced detectable increases in variability. This provides observational evidence of an intensifying hydrological cycle in northern Canada, consistent with other regions of the pan-Arctic domain.
We present a new measurement of air shower muons made during atmospheric ascent of the High Energ... more We present a new measurement of air shower muons made during atmospheric ascent of the High Energy Antimatter Telescope balloon experiment. The muon charge ratio mu+ / mu- is presented as a function of atmospheric depth in the momentum interval 0.3-0.9 GeV/c. The differential mu- momentum spectra are presented between 0.3 and about 50 GeV/c at atmospheric depths between 13 and 960 g/cm^2. We compare our measurements with other recent data and with Monte Carlo calculations of the same type as those used in predicting atmospheric neutrino fluxes. We find that our measured mu- fluxes are smaller than the predictions by as much as 70% at shallow atmospheric depths, by about 20% at the depth of shower maximum, and are in good agreement with the predictions at greater depths. We explore the consequences of this on the question of atmospheric neutrino production.
Recent trends and changes in the observed river discharge into Hudson, James, and Ungava Bays (HJ... more Recent trends and changes in the observed river discharge into Hudson, James, and Ungava Bays (HJUBs) for the period 1964-1994 will be presented. Forty-two rivers with outlets into these bays contribute on average 700 cubic kilometers (= 0.02 sverdrups) of freshwater to the Arctic Ocean. River discharge attains a mean annual peak of 4.2 cubic kilometers per day on average each 17 June for the system as a whole, whereas the minimum of 0.6 cubic kilometers occurs on average each 3 April. The Nelson River supplies as much as 30% of the daily discharge for the entire system during winter, but diminishes in relative importance during spring and summer. Runoff rates per contributing area are highest (lowest) on the eastern (western) shores of Hudson and James Bays. Linear trend analyses reveal decreasing discharge in 38 out of the 42 rivers over the 31-year period. By 1994, the total annual freshwater discharge into the Arctic Ocean diminished by 110 cubic kilometers from its values in 1964, equivalent to a reduction of 0.0035 sverdrups. The annual peak discharge rates associated with snowmelt advanced by 16 days between 1964 and 1994 and has diminished slightly in intensity. There is a direct correlation between the time of this hydrological event and the latitude of a river's mouth; the timing of the peak discharge rates varies by 5 days for each degree of latitude. Continental snowmelt induces a seasonal pulse of freshwater from HJUBs that is tracked along its path into the Labrador Current and that coincides with ocean salinity anomalies on the inner Newfoundland Shelf. The talk will end with a discussion on the implications of a changing freshwater regime in HJUBs.
Trends and variability in the 1964-2007 annual streamflow for 45 rivers spanning 5.2 × 106 km2 of... more Trends and variability in the 1964-2007 annual streamflow for 45 rivers spanning 5.2 × 106 km2 of northern Canada are investigated. Discharge averages 1153 km3 yr-1 with a standard deviation of 71.4 km3 yr-1 and coefficient of variation (CVQ) of 6.2% over the 44-year period. A trend analysis reveals a recent (1989-2007) 15.5% increase in the annual flows owing to much-above average values recorded over the past decade. Trends in CVQ computed from 11-year moving windows of annual streamflows exhibit spatially coherent signals with increasing variability across most of northern Canada, excluding some rivers with outlets to the Labrador Sea and eastern James Bay. For the period of interest, 46% and 30% of the available gauged area and river discharge, respectively, experienced detectable increases in variability. This provides observational evidence of an intensifying hydrological cycle in northern Canada, consistent with other regions of the pan-Arctic domain.
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Papers by Eric James Labrador