C-SIDE - Cycles of Sea-Ice Dynamics in the Earth system



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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- Document and synthesize records of sea-ice proxies in the Southern Ocean for the last 130,000 years using diatom assemblage data and complementary proxies of sea-ice changes.
- Coordinate taxonomic and statistical approaches to establish consistent and comparable representations of sea-ice extent between different regions of the Southern Ocean.
- Develop regional reconstructions of spatial and temporal changes in sea-ice dynamics as the Earth entered the last glacial period.
- Compare these reconstructions with contemporaneous regional reconstructions of environmental conditions, with a focus on ocean temperatures, nutrient utilization and productivity, and ocean circulation.
- Compare these proxy reconstructions with model simulations of sea-ice cover and regional oceanographic dynamics spanning the full glacial-interglacial cycle.


Helen Bostock (National Institute of Water and Atmospheric Research, New Zealand)
Xavier Crosta (University of Bordeaux, France)
Karen Kohfeld (Simon Fraser University, Canada)
Amy Leventer (Colgate University, USA)
Katrin Meissner (University of New South Wales, Australia)


Feb 2018

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.

c side sea ice cov fig

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)).

c side img 2 frag

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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