What do Paleoclimate . records tell us about . WAIS stability?

What Do West Antarctic Ice Cores Say About Rapid Ice Flow?

Ken TaylorRichard AlleyEd BrookHoward Conway Jeff Severinghaus Paul Mayewski Jim White

Byrd vs SDM

White & Brook

Warmer

Colder

Byrd vs SDM

White & Brook

Warmer

Colder

Byrd vs SDM

White & Brook

15 ka

22 ka

Warmer

Colder

Byrd vs SDM

White & Brook

Warmer

Colder

Gas records

kkks

Must be local change at Siple Dome because:

1) Change does not show up at Byrd

2) Proxies of distant climate (Dexcess and chemistry) do not show significant changes

Siple Dome Records

Gas records

kkks

Must be local change at Siple Dome because:

1) Change does not show up at Byrd

2) Proxies of distant climate (Dexcess and chemistry) do not show significant changes

Siple Dome Records

Disrupted stratigraphy

Regional Climate Change:Would see something at Byrd and in other climate proxies from SDM.

Regional Climate Change:Would see something at Byrd and in other climate proxies from SDM.

Mishandling of Core: Gas record/Deuterium record offset is correct

Regional Climate Change:Would see something at Byrd and in other climate proxies from SDM.

Mishandling of Core: Gas record/Deuterium record offset is correct

Folded Stratigraphy:No suitable ice to fold into record

Regional Climate Change:Would see something at Byrd and in other climate proxies from SDM.

Mishandling of Core: Gas record/Deuterium record offset is correct

Folded Stratigraphy:No suitable ice to fold into record

Ice Flow Overrode Siple DomeChange in record is too abruptNo other ice with right characterisitics

Regional Climate Change:Would see something at Byrd and in other climate proxies from SDM.

Mishandling of Core: Gas record/Deuterium record offset is correct

Folded Stratigraphy:No suitable ice to fold into record

Ice Flow Overrode Siple DomeChange in record is too abrupt

Interpretation 1: Elevation of Siple Dome Changed Lapse Rate

22 ka B.P. 6oC warming, ~200 years 600 m elevation decrease at SDM

15 ka B.P.3.5oC warming < 1,000? years350 m elevation decrease at

SDM

Ice Flow Modeling: Rapid 350 m decrease of Siple Dome

at 15 ka (Price et. al., 2007)

Atmospheric Modeling: Elevation of ice streams has large influence on temperature at Summit of Siple Dome(Monaghan & Bromwich, 2006)

Interpretation 1: Elevation of Siple Dome Changed Lapse Rate

22 ka B.P. 6oC warming, ~200 years 600 m elevation decrease at SDM

15 ka B.P.3.5oC warming < 1,000? years350 m elevation decrease at

SDM

Ice Flow Modeling: Rapid 350 m decrease of Siple Dome

at 15 ka (Price et. al., 2007)

Atmospheric Modeling: Elevation of ice streams has large influence on temperature at Summit of Siple Dome(Monaghan & Bromwich, 2006)

Interpretation 2: Elevation of Ice Streams Changed Air Flow Changed

Atmospheric Modeling: Elevation of ice streams has large influence on temperature at Summit of Siple Dome (Monaghan & Bromwich, 2006)Ice Sheet Model: Siple Dome was a bump (Dave Pollard)

SDMSDM

BYRDBYRD

Current situation Paleo situation

Some combination of:1) Changes in SDM surface elevation . (lapse rate)

2) Changes in ice stream elevation . (air flow patterns/katabatic winds)

At 15 ka and 22 ka there were large and rapid drawn downs of ice on the Siple Coast.

What caused ice draw down?

Sea level rise

Sub-ice flood

Ice shelf collapse

Ice stream internal dynamics

• ocean Explaination

Siple: White et al

Sea Level

The Siple Dome events precede the step increases in sea level.

What caused ice draw down?

Sea level rise

Sub-ice flood

Ice shelf collapse

Ice stream internal dynamics

`Eastern Ross SeaMosola & Anderson, 2006

Slope Gullies

Sub-ice water system

What caused ice draw down?

Sea level rise

Sub-ice flood

Ice shelf collapse

Ice stream internal dynamics

• MAP SHOWING

• Tdome, SDM, BYRD, Moulton, OCEAM COres

Roosevelt Island

RossIce Shelf

Siple Dome

http://lima.usgs.gov/access.php

• MAP SHOWING

• Tdome, SDM, BYRD, Moulton, OCEAM COres

Roosevelt Island

RossIce Shelf

Siple Dome

http://lima.usgs.gov/access.php

Water Temperature

Ice ShelfThickness

Bathymetry Siple and ShiraseCoasts are most vulnerable

David Holland

Water Temperature

Ice ShelfThickness

Bathymetry Siple and ShiraseCoasts are most vulnerable

David Holland

Water Temperature

Ice ShelfThickness

Bathymetry Siple and ShiraseCoasts are most vulnerable

David Holland

Water Temperature

Ice ShelfThickness

Bathymetry Siple and ShiraseCoasts are most vulnerable

David Holland

`Eastern Ross SeaMosola & Anderson, 2006

Iceberg furrows at 650 mNo sub-ice shelf deposits

Rapid retreat of grounded ice

• MAP SHOWING

• Tdome, SDM, BYRD, Moulton, OCEAM COres

Roosevelt Island

RossIce Shelf

Siple Dome

http://lima.usgs.gov/access.php

What caused ice draw down?

Sea level rise

Sub-ice flood

Ice shelf collapse

Ice stream internal dynamics

Siple Coast ice had large and rapid changes at 15 ka and 22 ka

Basal floodingBreak up of a portion of the Ross Ice ShelfIce stream internal dynamics

Amanda Mosola & John Anderson

Andy Monaghan, Dave Brom

*

Ignore this age; the simulation is for 15 ka

From dave pollard

pollard@essc.psu.edu