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Sea-ice growth, drift and deformation off Eastern Antarctica

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Heil, P (1999) Sea-ice growth, drift and deformation off Eastern Antarctica. PhD thesis, University of Tasmania.

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Abstract

Antarctic sea-ice thickness, concentration and extent all play a vital role in controlling
the exchange processes between ocean and atmosphere in the polar regions.
This study investigates how distributions of these characteristics are determined by
sea-ice growth, drift and deformation. Drift and deformation of East Antarctic sea
ice are investigated using in situ observations of sea-ice drift since the mid 1980s,
and results from numerical models. From the drift data a climatology of the East
Antarctic sea-ice velocity distribution is derived, and recurrent features in the drift
pattern are identified. The average daily drift speed in the westward flow near the
Antarctic coast is 0.22 m s -1(19.0 km d-1) with considerable spatial and temporal
variability. In the eastward flow north of the Antarctic Divergence the average is
0.17 m s -1(14.7 km d-1). The average ice motion over wide parts of the overall East
Antarctic sea-ice zone has a net northward component (0.04 m s -1or 3.5 km (1-1)
transporting pack ice equatorward. A new method is used to derive the mean winter
position of the Antarctic Divergence from ice-movement data. It is found that during
winter the Antarctic Divergence is further north than the mean annual position derived
from hydrographic measurements.
Thermodynamic ice growth near the coast of East Antarctica is modelled using field
data obtained since the late 1950s. The availability of atmospheric and some hydrographic
observations makes it possible to estimate the heat flux from the oceanic
mixed-layer to the underside of the sea ice. The magnitude of this oceanic-heat flux
is highest in early spring, and lowest in autumn. Annual mean values of the oceanicheat
flux vary between 5 and 12 W M-2 , with an average of 7.9 W M-2. On decadal
time-scales a decrease in oceanic-heat flux is found from the 1950s to 1980s for the area
studied. At sites close to the coast the annual maximum ice thicknesses are linked to
the extent of the cooling of the oceanic mixed-layer occuring in upstream polynyas.
Data from a regional experiment in the coastal current off Adelie Land yield new
insight into sea-ice deformation and the variability of forcing processes. Although
ice drift is dominated by long-term changes, sea-ice deformation exhibits significant
short-term variability. Numerical simulations show that in the absence of tidal forcing,
inertial motion can account for the formation of substantial open water within the
pack. Regional modelling shows that such a motion has a considerable impact on the
ice growth, and can roughly double the rate of ice production by allowing rapid growth
in recurrent open-water patches. This also significantly increases the amount of salt
rejected to the ocean.

Item Type: Thesis (PhD)
Keywords: Sea ice, Sea ice
Copyright Holders: The Author
Copyright Information:

Copyright 1999 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.)--University of Tasmania, 1999. Includes bibliographical references

Date Deposited: 19 Dec 2014 02:39
Last Modified: 23 May 2017 05:59
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