Control of Mode and Intermediate Water Mass Properties in Drake Passage by the

• Main Authors: Amundsen Sea Low, Sally E. Close, Alberto C. Naveira Garabato, Elaine L. Mcdonagh, Brian, A. King, Martin Biuw, Lars Boehme
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2012
• Subjects: Amundsen Sea; Antarctic; Bellingshausen Sea; Drake Passage; Pacific; Antarc*; Sea ice
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.660.1972; http://eprints.soton.ac.uk/355088/1/JCLI-D-12-00346.1-Close.pdf

The evolution of the physical properties of SubantarcticModeWater (SAMW) andAntarctic Intermediate Water (AAIW) in the Drake Passage region is examined on time scales down to intraseasonal, within the 1969–2009 period. Both SAMW and AAIW experience substantial interannual to interdecadal variability, significantly linked to the action of the Amundsen Sea low (ASL) in their formation areas. Observations suggest that the interdecadal freshening tendency evident in SAMWover the past three decades has recently abated, while AAIW has warmed significantly since the early 2000s. The two water masses have also expe-rienced a substantial lightening since the start of the record. Examination of the mechanisms underpinning water mass property variability shows that SAMW characteristics are controlled predominantly by a combi-nation of air–sea turbulent heat fluxes, cross-frontal Ekman transport of Antarctic surface waters, and the evaporation–precipitation balance in the Subantarctic zone of the southeast Pacific and Drake Passage, while AAIW properties reflect air–sea turbulent heat fluxes and sea ice formation in the Bellingshausen Sea. The recent interdecadal evolution of the ASL is consistent with both the dominance of the processes described here and the response of SAMW and AAIW on that time scale. 1.