New Zealand Journal of Marine and Freshwater Research abstracts
Variations in the East Auckland Current from satellite radar
altimeter data
ANDREW K. LAING
BASIL R. STANTON
National Institute of Water & Atmospheric
Research Ltd
P. O. Box 14-901, Kilbirnie
Wellington, New Zealand
PETER G. CHALLENOR
James Rennell Division for Ocean Circulation
Southampton Oceanography Centre
Southampton SO14 3ZH, England
Abstract We analysed satellite radar altimeter data for the
New Zealand area during the period November 1992 to June 1994. Sea-surface
height anomalies from the Topex-Poseidon and ERS-1 radar altimeter data were
consistent in locating and identifying variability within most of the
recognised major features in the area. Near the New Zealand coast, the tidal
models used in the analysis did not perform well. A considerable error in the
modelled M2 tidal component was apparent as an aliased signal with a period of
about 62 days (sampled at a 10 day orbital repeat period). A correction was
made to remove the error. Profiles of cross-track current anomalies were
deduced for the East Auckland Current system and there was good general
agreement between Topex-Poseidon and ERS-1 products. Using surface measurements
along one subsatellite track, the height data were calibrated and a history of
absolute cross-track currents to the north-east of North Cape was produced.
This showed a strong east-southeastward flow between 33.5deg.S and 34deg.S,
with a return flow meandering between 32deg.S and 33deg.S. The strength of the
current at a fixed location varied considerably, with a possible seasonal
influence. The histories of cross-track current-anomaly profiles, along with
current-anomaly vectors constructed for the track cross-over points, give a
coherent picture of features in the area. In particular, an anticyclonic eddy
to the north-east of New Zealand is identified moving south-eastward during the
spring of 1993.
Keywords satellite altimetry; East Auckland Current; dynamic
topography; Topex-Poseidon; ERS-1
New Zealand Journal of Marine and Freshwater Research, 1996: Vol. 30:
175-191
0028-8330/96/3002-0175 $2.50/0 (c) The Royal Society of New Zealand
1996
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