It was previously thought the northern limit for Southern Hemisphere sea ice was 55°S. But recent declines in surface air temperatures in southernmost South America have led to sea ice formation creeping 80 to 100 kilometers further north than previous estimates. Since 2000, sea ice has been extending well into 54°S.
The southernmost tip of South America has experienced rapid cooling in the last several centuries. In “the most recent decades” the climate has deteriorated to the coldest sea surface temperatures of the last 10,000 years (Bertrand et al., 2017).
Image Source: Bertrand et al., 2017
Not only has the sea ice around Antarctica been advancing in recent decades in tandem with Southern Ocean cooling (Fan et al., 2014), but the entire Southern Hemisphere’s sea ice extent has been creeping northwards since the 1970s (Comiso et al., 2017).
Image Source: Comiso et al., 2017
A new study (Salame et al., 2021) reports Southern Hemisphere sea ice has been creeping so far northwards since 2000 it now extends well into the 54°S southern Chilean fjords, perhaps 80 to 100 km further north than the NSIDC’s previous extension limit estimates (55°S).
The daily mean air temperatures in South America’s southernmost fjords fell below 0°C during 74% of the four months from June to September in 2015. Similar extended cold periods occurred throughout the 2000-2017 temperature record for this region.
These sustained sub-zero °C temperatures are considered the main reason sea ice has been forming during recent decades in all 13 of the Cordillera Darwin fjords analyzed.