Abstract
A fourth production region for the globally important Antarctic bottom water has been attributed to dense shelf water formation in the Cape Darnley Polynya, adjoining Prydz Bay in East Antarctica. Here we show new observations from CTD-instrumented elephant seals in 2011–2013 that provide the first complete assessment of dense shelf water formation in Prydz Bay. After a complex evolution involving opposing contributions from three polynyas (positive) and two ice shelves (negative), dense shelf water (salinity 34.65–34.7) is exported through Prydz Channel. This provides a distinct, relatively fresh contribution to Cape Darnley bottom water. Elsewhere, dense water formation is hindered by the freshwater input from the Amery and West Ice Shelves into the Prydz Bay Gyre. This study highlights the susceptibility of Antarctic bottom water to increased freshwater input from the enhanced melting of ice shelves, and ultimately the potential collapse of Antarctic bottom water formation in a warming climate.
Highlights
A fourth production region for the globally important Antarctic bottom water has been attributed to dense shelf water formation in the Cape Darnley Polynya, adjoining Prydz Bay in East Antarctica
The Prydz Bay Gyre (PBG) is associated with a relatively narrow coastal current that runs along the Amery Ice Shelf calving front, and continues westward after leaving Prydz Bay
Our inferred circulation agrees well with what was known about PBG, but suggests a more complex circulation along the ice shelf front than previously depicted
Summary
A fourth production region for the globally important Antarctic bottom water has been attributed to dense shelf water formation in the Cape Darnley Polynya, adjoining Prydz Bay in East Antarctica. Decades of speculation about a DSW source in Prydz Bay[11,12,13] ended after satellite-derived estimates of enhanced sea ice production (B180 km[3] per year)[14,15] in the Cape Darnley polynya (CDP) were directly linked to very saline DSW (434.8) using data collected by instrumented southern elephant seals[16] (Mirounga leonina). Extended periods of concentrated profiling of the water column around the periphery of the Prydz Bay Gyre (PBG) are available These unique observations in the key polynyas of Barrier Bay, Davis and MacKenzie Bay, and across the outflow region through Prydz Channel upstream of Cape Darnley, allows us to present a comprehensive picture of the evolution of DSW formation and export from Prydz Bay. Documenting the impact of ice shelves on polynya-driven AABW production, this study is timely given the growing evidence of 62° S 64° S
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