Preconditioning of Antarctic maximum sea-ice extent by upper-ocean stratification on a seasonal timescale

• Published in: Geophysical Research Letters
• Main Author: Su, Zhan
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: American Geophysical Union 2017
• Subjects: Antarctic sea ice; stratification; vertical heat flux; Ekman transport; Antarctic; Antarc*; Sea ice
• Online Access: https://doi.org/10.1002/2017GL073236

This study uses an observationally constrained and dynamically consistent ocean and sea ice state estimate. The author presents a remarkable agreement between the location of the edge of Antarctic maximum sea ice extent, reached in September, and the narrow transition band for the upper ocean (0–100 m depths) stratification, as early as April to June. To the south of this edge, the upper ocean has high stratification, which forbids convective fluxes to cross through; consequently, the ocean heat loss to the atmosphere is an efficient way to cool the surface ocean to the freezing point during April to September. To the north, the upper ocean has low stratification such that the ocean heat loss to the atmosphere is not efficient to cool the upper ocean. The upper ocean is instead cooled mainly through mixing with the colder inflow carried by northward Ekman transport but cannot reach the freezing point due to the nature of mixing. Therefore, upper ocean stratification, dominated by salinity here, provides an important constraint on the northward expansion of Antarctic sea ice to its maximum. © 2017 American Geophysical Union. Received 28 FEB 2017; Accepted 3 JUN 2017; Accepted article online 6 JUN 2017; Published online 22 JUN 2017. The data set used in this study can be obtained from the ECCO project website (http://ecco2.org/llc_hires). General discussions about ocean-ice interaction with Andy Thompson, Ron Kwok, Dimitris Menemenlis, Ian Fenty, Ou Wang, and Hong Zhang are gratefully acknowledged. Two anonymous reviewers provided helpful comments. This research was carried out, in part, at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (NASA). Z.S. was supported by a NASA Postdoctoral Program (NPP) Fellowship. Published - 21865f46476bfe54a973fbf0bd3d28a7706930fd943fc008aadc08992cdefb05.pdf Supplemental Material - grl56050-sup-0001-2017GL073236_SI.pdf