Antarctic landfast sea ice (fast ice) is sea ice held “fast” due to mechanical coupling with stationary coastal elements such as grounded icebergs, ice shelves or the coastline itself. Although relatively limited in areal coverage (~600,000 km2 in September) and width (up to 300 km), its distribution and variability have far-reaching consequences. It controls the size of coastal polynyas, thus influencing the formation of dense shelf water and modulating the formation of globally-important Antarctic Bottom Water; it protects vulnerable ice shelves from breakout due to exposure to the Southern Ocean; due to its considerable thickness, constitutes an important storage of freshwater and nutrients; and forms a key habitat element for a wide range of trophic levels. Despite its importance, knowledge of its distribution and other physical properties (especially roughness and snow cover), and the variability and trends of these, are limited due to difficulties associated with their automated retrieval from satellite data. We present the current state of knowledge of the physical properties of Antarctic fast ice, including its distribution, seasonality, variability, thickness and snow properties. We also synthesise the literature on interactions with the ocean and atmosphere – including both atmospheric/oceanic drivers of fast ice extent/thickness, as well as effects of the fast ice on the atmosphere and ocean. We summarise the shortcomings in our knowledge, and emphasise the dire need for prognostic fast ice representation in regional and circum-Antarctic coupled models. We also consider a qualitative view to likely changes in fast ice in 2100 using CMIP6 models. We conclude with a discussion of the observations required to progress our understanding of this key element of the Antarctic coastal environment.
Topic : Theme 1: Cryosphere monitoring.
Reference : T1-E14
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