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
Outline The issue: meltwater, Bolling-Allerod (B-A) and Younger
Dryas (YD) Model and data Drainage results Implications for climate dynamics
Inferred Greenland temperature
Thermohaline (THC) record (57W, 33N), McManus et al.,(Nature, 2004)
Barbados sea-level record
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
Deglacial drainage
Glacial Systems Model (GSM)
Margin forcing (Dyke, 2003)
Large ensemble approach
Bayesian calibration of 22 model parameters against a large set of paleo proxies
Drainage topography
Fast down-slope/storage surface drainage solver: dt=100 years
Coarse grained topography derived from HYDRO-1K DEM
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)
Deglacial eustatic sea-level chronology
Gulf of Mexico discharge 0.2 dSv present-
day flow Largest pulse
during mwp1-a inferred from observations
Gulf of Mexico discharge comparison
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
Hudson River discharge
Gulf of St. Lawrence discharge
Gulf of St. Lawrence sensitivity
NW arctic discharge
Arctic discharge sensitivity
Arctic discharge
YD onset drainage basins
Mississippi drainage NW Arctic drainage Labrador Sea drainage Gulf of St. Lawrence
drainage Hudson River drainage Pacific drainage
NW routing for Lake Agassiz
NW routing for Lake Agassiz sensitivity
Lake Agassiz choke point elevations
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
Climate and meltwater phasing
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
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