An abrupt transition in the Antarctic sea ice–ocean system
- 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.