How the Tasman Sea is leading to warming in the Antarctic Peninsula

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By combining observational data and numerical simulations, researchers have found that the warming of the Antarctic Peninsula is closely linked to what is happening in south-eastern Australia. The results were published on March 8 in the journal Nature communications.

While the planet is warming globally, this warming is not evenly distributed among the different regions of the world. Also, the north polar zone has experienced a temperature rise 2 to 3 times faster than the rest of the globe. This is also the case for the Antarctic Peninsula, where a significant fraction of the imposing southern cap sits.

The Antarctic Peninsula, a highly exposed region

In response to warming air and water, several ice barriers on the peninsula have collapsed in recent decades. Feedback A disintegrated in 1995, Feedback B in 2002 and the Wilkins platform in 2009. Finally, Feedback C experienced a partial collapse in 2017. This rapid development raised deep concerns in terms of influence on sea level rise. Indeed, the alteration of the ice barriers allows the ice placed on the bedrock to flow more freely towards the ocean.

Annual temperature trend between 1950 and 2020 (in ° C). Credits: NASA GISS.

To what extent does human-related climate change contribute to this trend? This is a major question that will determine the extent of the rise in ocean levels in the decades and centuries to come. Some work has suggested that the maximum warming observed on the peninsula is in part an effect of natural variability. In other words, a more or less complex redistribution of heat by internal fluctuations in the climate system.

Remote controlled warming

A new study published on March 8 attempted to more precisely assess the anthropogenic and natural contributions. At the end of their work, the researchers found that the rising temperatures on the peninsula and very related to what is happening in the Tasman Sea, in south-eastern Australia. Indeed, when it is abnormally hot, a train of atmospheric waves – called rossby waves – is generated (see illustration below).

antarctic peninsula
Pressure anomalies (low in blue, high in red) simulated in response to a warm anomaly in the Tasman Sea. Also, note the strengthening of the Amundsen depression as the wave train passes. Credits: Kazutoshi Sato et al. 2021.

The modification of the field of wind and pressure which they concretize propagates as far as Antarctica. The depression located in the Amundsen Sea eventually changed, so as to transport more soft and humid air towards the peninsula. A particularly marked effect in winter when the weather systems are the most developed. In 2015-2016, the Tasman Sea suffered a record sea heat wave which was quickly followed by climatic anomalies over the southern continent.

“We have shown that the warm winter episodes in the Tasman Sea influence the warm anomalies over key regions of West Antarctica, including the peninsula, through a shift towards the pole of the tracks of the South Pacific depressions. “, explains Kazutoshi Sato, lead author of the study. Thus, the results confirm that a significant part of the changes is remotely controlled by an internal redistribution of heat. Results which illustrate the complexity of climate change at the regional level.

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