C-SIDE - Cycles of Sea-Ice Dynamics in the Earth system
Summary Southern Ocean sea ice plays several important roles within the Earth system, affecting nutrient cycling and marine productivity, as well as modulation of air-sea gas exchange and deep-water formation in high latitudes. As sea ice changes in the future, it is important for our Earth-system models to be able to simulate the effects of these changes.
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Antarctic sea ice is an essential component of the Earth system; affecting global climate through modulation of Southern Hemisphere atmospheric circulation, global ocean overturning circulation, albedo and air-sea gas exchange in high latitudes, as well as nutrient cycling and marine productivity.
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Fig. 1: Changes in Antarctic sea-ice cover during 2016-2017, https://earthobservatory.nasa.gov/Features/WorldOfChange/sea_ice_south.php |
As Antarctic sea-ice cover is predicted to decrease in the next decades, it is essential for our Earth-system models to be able to simulate the effects of this waning. However, currently both modern and paleo data-model intercomparisons display large differences in sea-ice extent and trends. This affects the ability of these models to project the effects of sea-ice changes on the atmosphere, deep-ocean circulation and nutrient cycling.
Paleo-reconstructions of sea ice are often based on fossil assemblages of marine diatom species found in association with sea ice (see Fig.2). These reconstructions are pivotal to understand how Antarctic sea ice changed in the past, and how it influenced these physical and biogeochemical processes. However, most previous paleoclimate reconstructions of Southern Ocean sea ice have focused on the Last Glacial Maximum timeslice (CLIMAP, MARGO projects) or the Holocene and last interglacial periods (PAGES working group Sea Ice Proxies (SIP)).
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Fig. 2: Cryophilic Fragilariopsis such as F. obliquecotate are used in the diatom transfer functions used to reconstruct sea ice. Credit: Xavier Crosta |
Yet, our knowledge of changes in sea-ice cover as the Earth entered a full glacial period is limited to a handful of ocean records in the Southern Ocean. This lack of data limits our ability to establish the role of sea ice in large-scale reorganizations of ocean circulation and carbon sequestration entering a glaciation.
The aim of the C-SIDE working group is to reconstruct changes in sea-ice extent in the Southern Ocean for the past 130,000 years, reconstruct how sea-ice cover responded to global cooling as the Earth entered a glacial cycle, and to better understand how sea-ice cover may have influenced nutrient cycling, ocean productivity, air-sea gas exchange, and circulation dynamics.
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