Abstract
While the Northern Hemisphere sea-ice has uniformly declined over the past several decades, the observed sea-ice in the Southern Hemisphere has exhibited regions of increase and decrease. Here we use a comprehensive set of ocean-sea-ice simulations (1990-2007) to elucidate the drivers of the observed heterogeneous sea-ice trends. We show wind variability is an important determinant of the heterogeneous pattern of the variability and trends in Southern Hemisphere sea-ice. Only in the West Pacific region does Southern Annular Mode wind forcing contribute significantly to the trend in sea-ice duration. El Niño Southern Oscillation wind forcing contribution to the sea-ice duration trend is confined to the Atlantic and Pacific. In the Indian Ocean, weather is a significant driver of the sea-ice duration trend. Only in the East Pacific region is wind forcing alone insufficient to give rise to the observed sea-ice decline and must be augmented by warming to reproduce the observations.
Highlights
While the Northern Hemisphere sea-ice has uniformly declined over the past several decades, the observed sea-ice in the Southern Hemisphere has exhibited regions of increase and decrease
We present simulations to assess the regional response of sea-ice to Southern Annular Mode (SAM), El Nino Southern Oscillation (ENSO) and atmospheric weather forcings; the experiments are summarized in Table 1, with details given in the Methods section
With SAM wind forcing making a significant contribution to sea-ice duration trends in the East Pacific and ENSO wind forcing making a significant contribution to sea-ice duration trends in the Atlantic and Pacific
Summary
While the Northern Hemisphere sea-ice has uniformly declined over the past several decades, the observed sea-ice in the Southern Hemisphere has exhibited regions of increase and decrease. We show wind variability is an important determinant of the heterogeneous pattern of the variability and trends in Southern Hemisphere sea-ice. Only in the West Pacific region does Southern Annular Mode wind forcing contribute significantly to the trend in sea-ice duration. As previous studies have suggested that the Southern Annular Mode (SAM)[21,22], the El Nino Southern Oscillation (ENSO)[23,23] and the weather[24,25] may all be important factors in sea-ice variability and trends, a study to assess the dominant drivers is needed. In the East Pacific region is wind forcing alone insufficient to give rise to the observed sea-ice decline and must be augmented by warming to reproduce the observed trend
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