With shrinking sea ice, more light reaches the surface of the Arctic Ocean. Some have predicted that this will lead to more plankton, which in turn would support fish and other animals. Not so fast, says a team of scientists led by Princeton University and the Max Planck Institute for Chemistry. They point to nitrogen, a vital nutrient. The researchers used fossilized plankton to study the history of sources and supply rates of nitrogen to the western and central open Arctic Ocean. Their work, detailed in a paper in the current issue of the journal Nature Geoscience, suggests that under a global warming regime, these open Arctic waters will experience more intense nitrogen limitation, likely preventing a rise in productivity. “Looking at the Arctic Ocean from space, it’s difficult to see water at all, as much of the Arctic Ocean is covered by a layer of sea ice,” said lead author Jesse Farmer, a postdoctoral research associate in the Department of Geosciences at Princeton University who is also a visiting postdoctoral fellow at the Max Planck Institute for Chemistry in Mainz, Germany. This sea ice naturally expands during winters and contracts during summers. In recent decades, however, global warming has caused a rapid decline in summer sea ice coverage, with summer ice cover now roughly half that of 1979.
Did you know that Antarctica used to be ice-free and earth used to be 20 degrees warmer than it is now? Find out why climate change then wasn’t a problem, and why it is now with Princeton University’s Daniel Sigman. Also find out how climate change caused horses to grow from the size of large house cats to their size today. (Audio only) https://www.3takeaways.com/episodes/princeton-professor-daniel-sigman
Heat uptake by the ocean is slowing the greenhouse gas-driven warming of the atmosphere, and the ocean represents the dominant long-term sink for the carbon dioxide gas deriving from fossil fuel use. However, these beneficial roles of the ocean are tempered by the slowness with which surface waters are carried into the deep ocean, through a process known as “deep ocean ventilation” that occurs at high latitudes. Moreover, most global climate models have predicted that deep ocean ventilation will slow further in the future as global warming proceeds. The Southern Ocean around Antarctica is active in deep ocean ventilation and thus particularly important in the uptake of fossil fuel carbon dioxide and global warming heat. Evidence will be presented that deep ocean ventilation by the Southern Ocean was slower during past ice ages and faster during warm interglacial periods. These findings raise the possibility that deep ocean ventilation by the Southern Ocean will accelerate into the global warming future, counter to most model-based expectations. The origins and significance of this apparent disagreement will be discussed.
Prof. Daniel Sigman, co-author of the study "Iron Fertilization of the Sub-antarctic Ocean During the Last Ice Age" talks with Vancouver's CBC Radio One host Gregor Craigie on the scalability and viability of boosting salmon populations in coastal water off of British Columbia. (Audio only)