The role of the tropics in atmospheric forcing and ice sheet response in Antarctica on decadal to millennial timescales

Transcription

1 The role of the tropics in atmospheric forcing and ice sheet response in Antarctica on decadal to millennial timescales Eric Steig University of Washington Earth and Space Sciences Atmospheric Sciences Quaternary Research Center with major contributions from: Qinghua Ding David Battisti lots of others

2 Rapid ice sheet thinning in West Antarctica Pine Island Glacier Amundsen Sea Embayment West Antarctica East Antarctica Pritchard et al., 2012

3 Ice shelf thinning and deep water temperature Pine Island ice shelf Amundsen Sea Embayment West Antarctica East Antarctica Pritchard et al., 2012

4 Intrusion of CDW into the Amundsen Sea Embayment Colors show maximum temperature Pine Island ice shelf Figure courtesy of Pierre Dutriuex

5 2012 observations: CDW flow onto the shelf has decreased Figure courtesy of Pierre Dutriuex

6 2012 observations: CDW flow onto the shelf has decreased Nino4 SST Year Figure courtesy of Pierre Dutriuex

7 2012 observations: winds predominantly easterly Figure courtesy of Pierre Dutriuex

8 observations: major La Niña event SST colored shading and 200, 500 geopoten6al heights and SLP, from ERA- interim reanalysis Pine Island Glacier

9 West Antarctic δ 18 O anomalies vs. Niño4 anomalies O ( o / oo ) 2 WAIS Divide Niño Temperature Year Steig et al., 2013

10 Ice Core Sites in Antarc6ca WAIS Divide EDML Accumula6on Rate: 21.5 cm a- 1 Ice Thickness: 3460 m Average Temperature: - 30 C Gas- Age Ice- Age Difference: 208 years Byrd Vostok Dome C Site was selected to be similar to Greenland deep ice cores

11 Da6ng WAIS Divide by Electrical Measurements Photos: Bryan Holmes

12 Annual Layer Interpreta6on DC Normalized Conductance AC Depth (m) Fudge, Steig, et al, 2013

13 High resolu6on of WAIS Divide ice core Layer Count Byrd Isotope Match OpticalLog Depth (m) 2000 Age (ka) Age (ka) Annual Layer Thickness (m) Fudge, Steig, et al, 2013

14 High resolu6on of WAIS Divide ice core Layer Count Byrd Isotope Match OpticalLog Depth (m) 2000 Age (ka) to 2 cm thick annual layers Age (ka) Annual Layer Thickness (m) Fudge, Steig, et al, 2013

15 WAIS Divide δ 18 Ο Sample Resolu6on annual layering to 31 kyr 1/2 m samples not (yet) annually layer- counted Age (thousands of years) Sample Resolution (years) 18 O (per mil Depth, m 14

16 WAIS Divide δ 18 Ο vs. Age O (per mil) year averages Age, thousands of years before 2000 Fudge, Steig, et al,

17 WAIS Divide δ 18 Ο O (per mil) Fudge, Steig, et al,

18 WAIS Divide δ 18 Ο and global CH 4 18 O (per mil) CH 4 (ppbv) Age (ka) Ed Brook, Brad Markle, Eric Steig, unpublished 17

19 WAIS Divide δ 18 Ο and NGRIP δ 18 Ο 18 O (per mil) O (per mil) Fudge, Steig, et al,

20 WAIS Divide δ 18 Ο and global CH 4 18 O (per mil) CH 4 (ppbv) Age (ka) Brad Markle, Eric Steig, Ed Brook, unpublished 19

21 WAIS Divide dxs and global CH deuteriume excess (per mil) CH 4 (ppbv) Age (ka)

22 WAIS Divide dxs and global CH deuteriume excess (per mil) CH 4 (ppbv) Age (ka) Reminder: methane decreases when the N. Atlan6c cools. 21

23 Poleward shift of the westerlies in response to N Hem cooling Ceppi et al., 2013

24 Rainfall change in response to N Hem cooling rainfall change (m/year) 1.5 2

25 δ 18 O change in response to N Hem cooling O change (per mil) 3 4 5

26 Deuterium excess change in response to N Hem cooling dxs change (per mil) 3 4 5

27 Influence of moisture source location on dxs in Antarctic snow, from Petit, White et al., 1991 Interior Coast 26

28 Correlation of precipitation with the SAM index 27

29 Correlation of deuterium excess with the SAM index 28

30 Monin et al CO2 NADW McManus et al., 2004

31 Monin et al CO2 NADW McManus et al., 2004

32 Monin et al CO2 NADW McManus et al., 2004

33 WAIS Divide δ 18 Ο and dxs 3 Abrupt shift in the westerlies? deuteriume excess (per mil) O (per mil) Age (ka)

34 WAIS Divide δ 18 Ο and dxs 3 Abrupt shift in the westerlies? deuteriume excess (per mil) O (per mil) Age (ka)

35 WAIS Divide δ 18 Ο and dxs 3 Abrupt shift in the westerlies? deuteriume excess (per mil) O (per mil) Age (ka)

36 Summary and Next Steps 32

37 Summary and Next Steps Tropical variability has a profound influence on atmospheric circula6on at high Southern La6tudes- - - with implica6ons for ocean circula6on and ice sheet stability WAIS Divide is well situated to examine the tropical- extratropical teleconnec6ons through 6me WAIS Divide deuterium excess provides support for fast coupling between the D- O events and Antarc6c climate, through the tropical teleconnec6on. This is in addi6on to the lagged ocean circula6on response These data may provide support for the Heinrich event/southern Westerlies argument for the CO2 rise at the end of the last glacia6on 32

38 Thank you Funded by: U.S. Na6onal Science Founda6on Office of Polar Programs and the University of Washington Quaternary Research Center WAIS Divide field crew upon reaching 3330 m 33

39 34

40 WAIS Divide dxs and WAIS Divide Methane WAIS Divide deuterium excess CH 4 (ppbv) WAIS Divide Methane 8.2 ka deuterium excess (per mil) Age (years before 2000) Methane data (preliminary) from T. Sowers 35

41 WAIS Divide δ 18 O and WAIS Divide Methane WAIS Divide δ 18 O 33 CH 4 (ppbv) O (per mil) 600 WAIS Divide Methane 8.2 ka Age (years before 2000) Methane data (preliminary) from T. Sowers 36