Details

Autor(en) / Beteiligte

• WAIS Divide Project Members

Titel

Onset of deglacial warming in West Antarctica driven by local orbital forcing

Ist Teil von

• Nature (London), 2013-08, Vol.500 (7463), p.440-444

Ort / Verlag

London: Nature Publishing Group UK

Erscheinungsjahr

2013

Quelle

Psychology & Behavioral Sciences Collection

Beschreibungen/Notizen

• An annually resolved ice-core record from West Antarctica indicates that warming driven by local insolation resulting from sea-ice decline began in that region about 2,000 years before warming in East Antarctica, reconciling two alternative explanations for deglacial warming in the Southern Hemisphere. Local conditions drive Antarctic deglaciations There are two main theories vying to explain Antarctic climate changes at the time of Northern Hemisphere deglaciations. One holds that changes in ocean circulation — driven by changes in Northern Hemisphere insolation — govern Southern Hemisphere climate. The other argues for a dominant influence from local changes in insolation. It has been difficult to differentiate between the two because of the low resolution of many ice-core records. Now Tyler Fudge and colleagues present an annually resolved ice-core record from the West Antarctic Ice Sheet Divide site and reveal an increase in snowfall about 18,000 years ago, preceded by a distinct warming 20,000 years ago. Changes in local insolation and nearby sea ice appear to be the cause of the early warming, suggesting that East and West Antarctica may respond to different deglacial forcings. The cause of warming in the Southern Hemisphere during the most recent deglaciation remains a matter of debate 1 , 2 . Hypotheses for a Northern Hemisphere trigger, through oceanic redistributions of heat, are based in part on the abrupt onset of warming seen in East Antarctic ice cores and dated to 18,000 years ago, which is several thousand years after high-latitude Northern Hemisphere summer insolation intensity began increasing from its minimum, approximately 24,000 years ago 3 , 4 . An alternative explanation is that local solar insolation changes cause the Southern Hemisphere to warm independently 2 , 5 . Here we present results from a new, annually resolved ice-core record from West Antarctica that reconciles these two views. The records show that 18,000 years ago snow accumulation in West Antarctica began increasing, coincident with increasing carbon dioxide concentrations, warming in East Antarctica and cooling in the Northern Hemisphere 6 associated with an abrupt decrease in Atlantic meridional overturning circulation 7 . However, significant warming in West Antarctica began at least 2,000 years earlier. Circum-Antarctic sea-ice decline, driven by increasing local insolation, is the likely cause of this warming. The marine-influenced West Antarctic records suggest a more active role for the Southern Ocean in the onset of deglaciation than is inferred from ice cores in the East Antarctic interior, which are largely isolated from sea-ice changes.