lev tarasov and w. r. peltier university of toronto
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A new calibrated deglacial drainage history for North America and evidence for an Arctic trigger for the Younger Dryas. Lev Tarasov and W. R. Peltier University of Toronto. Outline. The issue: meltwater, Bolling-Allerod (B-A) and Younger Dryas (YD) Model and data Drainage results - PowerPoint PPT PresentationTRANSCRIPT
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A new calibrated deglacial drainage history for North America and
evidence for an Arctic trigger for the Younger Dryas
Lev Tarasov and W. R. PeltierUniversity of Toronto
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Outline The issue: meltwater, Bolling-Allerod (B-A) and Younger
Dryas (YD) Model and data Drainage results Implications for climate dynamics
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Inferred Greenland temperature
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Thermohaline (THC) record (57W, 33N), McManus et al.,(Nature, 2004)
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Barbados sea-level record
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More challenges
Champlain Sea was at highest salinity during YD onset (Rodrigues and Vilks, QSR, 1994)
High surface salinity for Gulf of St. Lawrence during YD (de Vernal et al., Nature,1996)
Muddy water sinks (Parsons et al., Sed., 2001) With sediment loads as low as 1 kg/m^3
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Deglacial drainage
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Glacial Systems Model (GSM)
Margin forcing (Dyke, 2003)
Large ensemble approach
Bayesian calibration of 22 model parameters against a large set of paleo proxies
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Drainage topography
Fast down-slope/storage surface drainage solver: dt=100 years
Coarse grained topography derived from HYDRO-1K DEM
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Drainage ensembles 50 member sub-ensembles Best from Bayesian
calibration: 92A, but strandline misfits ->
Further hydrological tuning: 11P, 11Y
Red River (RR) Wampum (W) Lake Athabasca (A) Great Slave Lake (GS) Great Bear Lake (GB)
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Deglacial eustatic sea-level chronology
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Gulf of Mexico discharge 0.2 dSv present-
day flow Largest pulse
during mwp1-a inferred from observations
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Gulf of Mexico discharge comparison
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mwp1-a drainage map Mississippi drainage NW Arctic drainage Labrador Sea drainage Gulf of St. Lawrence
drainage Hudson River drainage Pacific drainage -14.6 kyr Mississippi
discharge: 0.34 dSv -14.4 kyr Mississippi : 1.7
dSv
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Hudson River discharge
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Gulf of St. Lawrence discharge
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Gulf of St. Lawrence sensitivity
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NW arctic discharge
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Arctic discharge sensitivity
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Arctic discharge
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YD onset drainage basins
Mississippi drainage NW Arctic drainage Labrador Sea drainage Gulf of St. Lawrence
drainage Hudson River drainage Pacific drainage
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NW routing for Lake Agassiz
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NW routing for Lake Agassiz sensitivity
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Lake Agassiz choke point elevations
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Where does the meltwater go? Bauch et al (QSR,
2001): evidence of a low salinity event at or before YD onset in western Fram Strait
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Climate and meltwater phasing
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Summary
Largest (1.7 to 2.3 dSv over 100 years) discharge into the NW Arctic Basin during YD onset
Most of NW discharge is due to the reduction of the Keewatin ice dome: thus independent of Lake Agassiz routing uncertainties
Trigger for YD? Ensemble NA contributions to mwp-1a range from 7.2 to
11.4 m eustatic Large (1.5-2 dSv over 100 years) meltwater pulses into both
the Gulf of Mexico and Eastern seaboard GSM + calibration = data and physics integration