Scientists from the McGill University and University of Pennsylvania have gathered conclusive evidence to show that climate change is the main reason for the disappearance of ice-free regions in the Arctic known as polynya.
The polynya was first observed in the Weddell Sea in the 1970s and it has not reappeared after 40 years. Scientists have been studying about this phenomenon's origins and researchers concluded that the last appearance of the polynya may be its last, because climate change is trapping warm water in beneath the ocean, preventing the formation of ice-free regions.
Analyzing data from measurements made by robotic floats and ship that sail around the Antarctica for the last six decades, the researchers concluded that climate change affects the ocean's salinity, trapping the warm waters below.
"Deep ocean waters only mix directly to the surface in a few small regions of the global ocean, so this has effectively shut one of the main conduits for deep ocean heat to escape," stated Casimir de Lavergne in a press release. Lavergne is the study lead author and graduate of McGill's Master in Atmospheric and Oceanic Sciences.
The study also showed that the freshwater lid trapping the warmer waters below are increasing due to more precipitation in the area. According to Jaime Palter, co-author of the studyand a professor in McGill's Department of Atmospheric and Oceanic Sciences, the polar ocean has become wetter and this new source of freshwater will prevent polynyas from resurfacing.
Furthermore, the new study may explain why the Antarctic Bottom Water has been declining throughout the years.
Eric Galbraith, study co-author and professor of McGill's Department of Earth and Planetary Sciences explains that, "The waters exposed in the Weddell polynya became very cold, making them very dense, so that they sunk down to become Antarctic Bottom Water that spread throughout the global ocean. This source of dense water was equal to at least twice the flow of all the rivers of the world combined, but with the surface capped by freshwater, it has been cut off."
This study was published in the Mar. 2 issue of Nature Climate Change.