The study is based on over three decades of atmospheric data and the study further identifies new ways in which distant regional conditions are contributing to Antarctic climate change. The study is published in the journal Nature.
"Our findings reveal a previously unknown—and surprising—force behind climate change that is occurring deep in our southern hemisphere: the Atlantic Ocean," says Xichen Li, a doctoral student in NYU's Courant Institute of Mathematical Sciences and the study's lead author. "Moreover, the study offers further confirmation that warming in one region can have far-reaching effects in another."
The Antarctica has experienced dramatic climate change over the past few decades. Its peninsula has experienced the strongest warming on the planet. Antarctic changes during its summer have been attributed to greenhouse gas increase and stratospheric ozone loss. However, forces behind the climate change during winter are less clear. Moreover, the effects of changes during the cold season are of complex nature making it difficult to identify the atmospheric culprit.
Scientists have known for long that the distant Pacific Ocean affects the Antarctic climate in part. However, the El-Nino brought about by Pacific have short term influence. Long term forces that have produced warming along the Antarctic are less understood. These long term forces have produced warming along the Antarctic Peninsula or the sea-ice redistribution in the southern hemisphere's winter over many decades.
In order to address this question, the NYU researchers focused on the Atlantic Ocean which has been overlooked as a force behind Antarctic climate change. More specifically, the scientists studied the North and Tropical Atlantic's Sea Surface Temperature (SST) variability—changes in the ocean's surface temperature—focusing on the last three decades. The metric, the Atlantic Multidecadal Oscillation(AMO) had previously not been considered in seeking explanations for Antarctic climate change.
The scientists found strong correlations between changes in the North and Tropical Atlantic's SST and subsequent changes in Antarctic climate when they used a time-series analysis. The scientists observed that warming Atlantic waters were followed by changes in sea-level pressure in the Antarctic's Amundsen Sea. Further, the warming patterns also preceded redistribution of sea ice between the Antarctic's Ross and Amundsen-Bellingshausen-Weddell Seas.
The research comprised of the use of observational data and computer modeling.The observational data, found a link, or correlation, between the Atlantic and Antarctic data sets. However, a correlation does not explain what may be causing a phenomenon. The second part of the study used a global atmospheric model, which allowed the researchers to create a simulated warming of the North Atlantic. The model responded, as the researchers had suspected, by "changing" the climate in Antarctica.
"While our data analysis showed a correlation, it was the use of a state-of-the-art computer model that allowed us to see that North Atlantic warming was causing Antarctic climate change and not vice versa," said David Holland, co-author of the study, a professor at NYU's Courant Institute and past director of NYU's Center for Atmospheric Ocean Science.
The study's findings show that Antarctic sea-ice change is fundamentally different from the well-reported changes in the Arctic. In contrast to the sea-ice decline over the Arctic, Antarctic sea ice has not diminished. Rather, it has redistributed itself in ways that have perplexed scientists, with declines in some areas and increases in others. "From this study, we are learning just how Antarctic sea-ice redistributes itself, and also finding that the underlying mechanisms controlling Antarctic sea ice are completely distinct from those in the Arctic," Holland said
(Photograph By: Jefferson Beck/NASA IceBridge, National Science Foundation)
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