Interaction Between Antarctic Circumpolar Current Eddies and the Sea Ice
Edge: Influence on Sea Ice Extent
Abstract
Multi-decadal expansion in the winter maximum sea ice extent (SIE)
around Antarctica was interrupted by contraction, beginning in 2016 and
continuing into 2019. This unexpected behavior motivates a closer look
at factors controlling the position of the outer ice margin.We analyzed
sea ice concentration (SIC) estimates derived from passive microwave
sensors with differing resolutions (SSM/I, AMSR-E and AMSR2) to identify
spatial and temporal statistics of the sea ice edge deVned by 15% SIC.
The low-pass Vltered position of the ice edge is similar in different
products, with the maximum northward position determined by proximity to
the relatively warm waters of the Antarctic Circumpolar Current. Higher
resolution SIC products reveal greater spatial detail along the
convoluted margin, resulting in a relatively longer sea ice perimeter.
Spectral analysis does not identify statistically signiVcant peaks in
length scales along the margin; however, visual comparison with
geostrophic velocities and sea surface temperature inferred from
satellite altimetry suggests that advection of sea ice by mesoscale
eddies is an important mechanism for deforming the ice edge in some
regions, such as the Bellingshausen Sea. We analyze a high-resolution
(dx=5 km), coupled ocean-sea ice model which realistically represents
the annual expansion of sea ice to quantify the dynamic and
thermodynamic roles of eddies in sea-ice mass balance and SIE. These
eddy effects on the sea ice edge are not well represented in
coarser-grid ocean reanalysis products such as ECCO-2, motivating an
investigation of how to represent eddy/sea-ice interactions in global
climate models.