January and February 2013 brought some unusual ice behavior in the Weddell Sea, east of the Antarctic Peninsula, as sea ice pushed northward toward warmer latitudes. On February 5, 2013, the National Snow and Ice Data Center (NSIDC) reported that the ice edge was roughly 200 to 300 kilometers (100 to 200 miles) north of what is normal for this time of year.
Ice lingered north of the Weddell Sea on February 22, 2013, when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite acquired this natural-color image. This image has been rotated so that north is toward the upper right. The coastline of the Antarctic Peninsula appears as a gray line. Just off the thin peninsula is the Larsen C ice shelf; beyond that there is sea ice.
Walt Meier, a scientist at NSIDC, noted both the unusual location and the unusual condition of sea ice. Just off the edge of the Larsen C Ice Shelf, ice in the Weddell Sea appeared closely packed, with few areas of open water. “Compared to the ice in the Weddell Sea proper, sea ice in the north is very diffuse, broken up, and thin,” Meier observed. But at this time of year, the region north of the Weddell Sea typically has little or no ice at all. So even though the ice north of the Weddell Sea is thin, it’s more ice than normally occurs.
Winds played a crucial role in driving the ice northward. NSIDC attributed the unusual pattern to “persistent high pressure in the region west of the Weddell Sea, across the Antarctic Peninsula to the Bellingshausen Sea.” (See this map of Antarctica for more information.) NSIDC explained that the high-pressure caused winds to blow from south to north on the east side of the Antarctic Peninsula. These winds not only pushed ice toward the middle latitudes; it also carried cold air northward. The frigid air impeded surface melting of the sea ice, keeping it frozen as it moved north.
Compared to sea ice in the Arctic, Antarctic sea ice generally shows greater variability. Unlike Arctic sea ice, which is confined to an ocean basin and surrounded by land, Antarctic sea ice fringes a continent. It has more room to grow in the winter and melts more completely in the summer. Moreover, Antarctic ice is subject to a wider range of influences from land, the atmosphere, and the ocean.