Sea‐Ice Induced Southern Ocean Subsurface Warming and Surface Cooling in a Warming Climate ...

• Main Authors: Haumann, Alexander, Gruber, Nicolas, Münnich, Matthias
• Format: Article in Journal/Newspaper
• Language: English
• Published: ETH Zurich 2020
• Subjects: Southern Ocean; sea ice; glacial meltwater; cooling; warming; freshwater; Antarc*; Antarctica; Sea ice
• Online Access: https://dx.doi.org/10.3929/ethz-b-000415934; http://hdl.handle.net/20.500.11850/415934

Much of the Southern Ocean surface south of 55° S cooled and freshened between at least the early 1980s and the early 2010s. Many processes have been proposed to explain the unexpected cooling, including increased winds or freshwater fluxes. However, these mechanisms so far failed to fully explain the surface trends and the concurrent subsurface warming (100 to 500 m). Here, we argue that these trends are predominantly caused by an increased wind‐driven northward sea‐ice transport, enhancing the extraction of freshwater near Antarctica and releasing it in the open ocean. This conclusion is based on factorial experiments with a regional ocean model. In all experiments with an enhanced northward sea‐ice transport, a strengthened salinity‐dominated stratification cools the open‐ocean surface waters between the Subantarctic Front and the sea‐ice edge. The strengthened stratification reduces the downward mixing of cold surface water and the upward heat loss of the warmer waters below, thus warming the subsurface. ... : AGU Advances, 1 (2) ...