Supercooled Southern Ocean Waters

Abstract

<p>In cold polar waters, temperatures sometimes drop below the freezing point, a process referred to as supercooling. However, observational challenges in polar regions limit our understanding of the spatial and temporal extent of this phenomenon. We here provide observational evidence that supercooled waters are much more widespread in the seasonally ice-covered Southern Ocean than previously reported. In 5.8% of all analyzed hydrographic profiles south of 55° S, we find temperatures below the surface freezing point (‘potential’ supercooling), and half of these have temperatures below the local freezing point (‘in-situ’ supercooling). Their occurrence doubles when neglecting measurement uncertainties. We attribute deep coastal-ocean supercooling to melting of Antarctic ice shelves, and surface-induced supercooling in the seasonal sea-ice region to winter-time sea-ice formation. The latter supercooling type can extend down to the permanent pycnocline due to convective sinking plumes—an important mechanism for vertical tracer transport and water-mass structure in the polar ocean.</p>

Deep-sea benthic foraminiferal response to the early Oligocene cooling: a study from the Southern Ocean ODP Hole 1138A

“…The current oceanographic setting of the Southern Ocean is established after many tectonic and oceanographic changes in the past. It changed over time and became a primary source of cold deep-water mass (Lawver and Gahagan 2003;Haumann et al 2020). It behaves like a buffer zone of all the water masses; here, all the primary ocean water gets mixed and distributed throughout the world ocean by the water circulation process (thermohaline circulation).…”