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- Title
Sea Ice Changes in the Pacific Sector of the Southern Ocean in Austral Autumn Closely Associated With the Negative Polarity of the South Pacific Oscillation.
- Authors
Yu, Lejiang; Zhong, Shiyuan; Vihma, Timo; Sui, Cuijuan; Sun, Bo
- Abstract
We present an explanation for the sea ice concentration trends in the Pacific sector of the Southern Ocean (PSSO) in austral autumn (April‐June) during 1979–2018. Sea ice has decreased in the Bellingshausen Sea and increased in the Ross Sea, concurrently with a negative trend in the South Pacific Oscillation (SPO). SPO statistically explains 43% of the sea ice concentration trend averaged over PSSO. Convective activities over East Africa and the southwestern Indian Ocean, the Interdecadal Pacific Oscillation (IPO), and extratropical processes excite a wavetrain that propagates from the Indian Ocean to the Southern Ocean and South America. The wavetrain contributes to the decrease of the autumn SPO index, which influences sea ice changes over PSSO. During the negative phase of SPO, an anomalous surface anticyclonic wind field over high‐latitude South Pacific Ocean generates anomalous sea ice concentrations via heat advection and wind forcing on ice drift. Plain Language Summary: Antarctic sea ice cover has experienced regionally different trends. In austral autumn, sea ice has decreased in the Bellingshausen Sea and increased in the Ross Sea, but reasons for these trends are not well understood. We present an explanation for the observed sea ice concentration trends in the Pacific sector of the Southern Ocean (PSSO) in austral autumn (April‐June) during 1979–2018. During this period, a large‐scale atmospheric circulation pattern, the South Pacific Oscillation (SPO), has had a trend towards its negative phase. This SPO trend statistically explains 43% of the sea ice concentration trend averaged over PSSO. The physical mechanisms are related to atmospheric teleconnections. Convective activities over East Africa and the southwestern Indian Ocean, the Interdecadal Pacific Oscillation (IPO), and extratropical processes excite a planetary wavetrain that propagates from the Indian Ocean to the Southern Ocean and South America. The wavetrain contributes to the decrease of the autumn SPO index, which influences sea ice changes over PSSO. During the negative phase of SPO, an anomalous surface anticyclonic wind field over high‐latitude South Pacific Ocean generates anomalous sea ice concentrations via heat advection and wind forcing on ice drift. Key Points: The autumn South Pacific Oscillation (SPO) index shows a decreasing trend for the 1979–2018 periodThe negative trend in autumn SPO index explains 43% of the total sea ice trend averaged across the Pacific sector of the Southern OceanAn anomalous wavetrain from over the Indian Ocean to the Southern Ocean contributes to the decrease of the autumn SPO index
- Subjects
EAST Africa; SOUTH America; OCEAN; SEA ice drift; OSCILLATIONS; ANTARCTIC oscillation; ANTARCTIC ice; AUTUMN
- Publication
Geophysical Research Letters, 2021, Vol 48, Issue 7, p1
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2021GL092409