EGU23-8749, updated on 26 Feb 2023
https://doi.org/10.5194/egusphere-egu23-8749
EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

An abrupt transition in the Antarctic sea ice–ocean system

F. Alexander Haumann1, François Massonnet2, Paul R. Holland3, Mitchell Bushuk4, Ted Maksym5, Will Hobbs6,7, Michael P. Meredith3, Ivana Cerovečki8, Thomas Lavergne9, Walter N. Meier10, Marilyn Raphael11, and Sharon Stammerjohn12
F. Alexander Haumann et al.
  • 1Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany (alexander.haumann@gmail.com)
  • 2Georges Lemaître Centre for Earth and Climate Research, Earth and Life Institute, Université catholique de Louvain, Louvain-la-Neuve, Belgium
  • 3British Antarctic Survey, Cambridge, United Kingdom
  • 4National Oceanic and Atmospheric Administration/Geophysical Fluid Dynamics Laboratory, Princeton, NJ, United States of America
  • 5Woods Hole Oceanographic Institution, Woods Hole, MA, United States of America
  • 6Australian Antarctic Program Partnership, Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia
  • 7ARC Centre of Excellence for Climate Extremes, University of Tasmania, Hobart, Australia
  • 8Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, United States of America
  • 9Research and Development Department, Norwegian Meteorological Institute, Oslo, Norway
  • 10National Snow and Ice Data Center, Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, United States of America
  • 11Department of Geography, University of California Los Angeles, Los Angeles, CA, United States of America
  • 12Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO, United States of America

Over the past decade, Antarctic sea ice extent exhibited a sequence of record maxima, followed by a rapid decline in 2015/16, and record minima since. In this presentation, we show that this sudden and remarkable ice loss marks an abrupt transition from a high to a low ice state that cannot be explained by year-to-year variability. Instead, it is most likely associated with a longer term variability arising from ice–ocean feedbacks. The abrupt transition was preceded by a multi-decadal increase in persistence and variance of the sea ice anomalies, an increasing upper Southern Ocean density stratification, and an accumulation of heat at the subsurface; suggesting a decoupling of the surface from the subsurface ocean. During this period, the sea ice anomalies shifted from being structured predominantly regionally and seasonally to a largely circumpolar and interannual regime. In 2015/16, the upper ocean density stratification in the ice-covered region suddenly weakened, leading to a release of heat from the subsurface, contributing to the sea ice decline during winter. Our analysis suggests that the sudden sea ice loss in 2015/16, and the persisting low ice conditions since, arose from a systematic change in the physical state of the coupled circumpolar ice–ocean system. This change will have wide implications for global climate, ecosystems, and the Antarctic Ice Sheet.

How to cite: Haumann, F. A., Massonnet, F., Holland, P. R., Bushuk, M., Maksym, T., Hobbs, W., Meredith, M. P., Cerovečki, I., Lavergne, T., Meier, W. N., Raphael, M., and Stammerjohn, S.: An abrupt transition in the Antarctic sea ice–ocean system, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-8749, https://doi.org/10.5194/egusphere-egu23-8749, 2023.