ABSTRACT
Sea ice is a key element in the climate system that regulates the exchanges of heat, mass, and momentum between the atmosphere and the oceans at high latitudes. Using the sea-ice extent (SIE) data generated from a series of passive microwave sensors, we discuss the variability of SIE trends for the Weddell Sea (WS), Indian Ocean (IO), western Pacific Ocean (PO), Ross Sea (RS), and Bellingshausen and Amundsen Seas (BAS), highlighting their magnitude for each of the four decades: 1979–1988, 1989–1998, 1999–2008, 2009–2018, and the role of the atmosphere/ocean and climate indices such as Pacific Decadal Oscillation (PDO), Atlantic Meridional Oscillation (AMO), Southern Oscillation Index (SOI), and Southern Annular Mode (SAM). The WS exhibited a negative SIE trend for all seasons during 2009–2018 and 1979–1988 (except for spring), and positive trends during 1999–2008 and 1989–1998 (except for summer). The IO sector exhibited negative trends for all seasons during 1979–1988 (except for spring), 1989–1998, and 2009–2018, while positive trends were observed during 1999–2008. A significant SIE trend was detected for IO in the autumn (−20.12%/decade). With negative trends during 1979–1988, the SIE in the PO sector showed positive trends during 1989–1998, 1999–2008 (except for autumn and winter), and 2009–2018 (except for spring). We encountered a significant SIE trend in winter during 1989–1998 (16.38%/decade). During 1979–1988 and 1989–1998, the SIE showed positive trends in the RS sector, and negative trends during 1999–2008 (except for spring) and 2009–2018. Trends significant were encountered in the RS in summer (74.48%/decade) and spring (21.26%/decade) during 1979–1988, and in winter (−11.89%/decade) during 2009–2018. With negative trends during 1979–1988 and 1999–2008, we detected positive trends during 1989–1998 (except for spring) and 2009–2018 (except for autumn and spring). We consolidate the inferences that explain the interconnection between local and remote drivers for explaining the SIE variability. There is an urgent need to review the model physics and better parameterization for the physical mechanisms to faithfully reproduce the observed SIE trends.
