Atmosphere Ocean Science Colloquium

Origin of CDW Intruding onto the Amundsen and Bellingshausen Sea Shelves

Speaker: Yoshihiro Nakayama, JPL

Location: Warren Weaver Hall 905

Date: Tuesday, June 26, 2018, 11 a.m.


Melting of West Antarctic ice shelves and glaciers is caused by Circumpolar Deep Water (CDW) intruding onto the Amundsen and Bellingshausen Seas (ABS) continental shelves. We investigate CDW pathways onto the ABS using a regional ocean model that extends from Antarctic Continent to 65ºS and from 140ºW to 65ºW.  The numerical experiments comprise simulations forced by the four possible combinations of 2001-2006 and 2009-2014 lateral-oceanic and surface-atmospheric boundary conditions. Simulated CDW tracers from a zonal section across 67ºS (S04P) circulate along the Antarctic Circumpolar Current (ACC) and Ross Gyre (RG) and travel into ABS continental shelf after 3-5 years but source locations are shifted westward by ~900 km along S04P in 2001-2006 compared to 2009-2014. We find that simulated off-shelf CDW is ~0.2ºC warmer in 2009-2014 case than in 2001-2006 case together with changes in simulated ocean circulation, leading to a ~0.1ºC warming of on-shelf CDW near eastern Amundsen Sea ice shelves. These differences are primarily caused by lateral, rather than surface, boundary conditions, implying that large-scale atmospheric and ocean circulation outside of our regional model domain is able to control CDW pathways and thus off- and on-shelf CDW properties.