Researchers linked ocean circulation to phenomenon in which the Arctic has warmed and steadily lost sea ice and while Antarctica has cooled and potentially even gained ice.
MIT computer simulations suggest Ocean around Antarctica and in the North Atlantic Ocean, but doesn't stay there; the moving ocean then distributes the heat. In the Southern Ocean the currents pull heat towards the equator and away from Antarctica. In the North Atlantic a different northward-flowing current moves heat into the Arctic. This process causes Antarctica to warm only mildly while the Arctic's temperature increases rapidly, accelerating sea ice loss.
The group also showed the ocean's response to the ozone hole helps explain the lack of warming around Antarctica. When the team factored the ozone hole into the model the winds over the Southern Ocean increased in speed and moved south, this cools the sea surface but triggers a slow process of warming and sea-ice shrinkage.
"Around Antarctica, the ozone hole may have delayed warming due to greenhouse gases by several decades," Marshall says. "I'm tempted to speculate that this is the period through which we are now passing. However, by 2050, ozone hole-effects may instead add to the warming around Antarctica, an effect that will diminish as the ozone hole heals.," said John Marshall, the Cecil and Ida Green Professor of Oceanography at MIT.
The findings provide insight into the effect of greenhouse gases and the ozone hole on polar climates.
"The researchers present a useful and timely reminder that the ocean is not a passive bath tub when it comes to climate change, but play an active role in shaping the spatial structure of climate change," said Richard Seagar, the Palisades Geophysical Institute/Lamont Research Professor at the Lamont-Doherty Earth Observatory, who was not involved in the study. "The work will likely motivate a lot of future work to better determine how the spatial patterns and temporal evolution of past and future climate change are influenced by an active ocean and its coupling back to the atmosphere."
