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Deep Seas and Climate Change

The effects of global warming reach all areas of the planet, including the ocean’s deepest levels. New research suggests that deep-sea trenches may also play an important role in climate change. New analyses of 20,000-year-old marine fossils show that changes in ocean circulation sparked by periods of global cooling led to the collapse of entire marine ecosystems. Scientists studied samples of ocean floor sediment from the Atlantic and found miniscule bivalved crustaceans in each layer. The presence of such crustaceans indicates a healthy deep-sea community, but other examined layers lacked evidence of the species. These layers were deposited during periods of natural cooling, when opportunistic species that thrive among decay flourished.
Scientists believe that the restoration of species diversity after a particularly intense cooling period may have taken thousands of years, and concluded that the ecosystem collapse could have resulted from natural cooling or anthropogenic warming in the face of altered current circulation patterns. The study confirms that the entire planet, including the deep seas, is at risk for great change if global warming continues.

Groundbreaking experiments have recently shown that deep sea trenches may have a significant role in climate change. Scientists have discovered that the deepest parts of the Earth’s oceans trap far more carbon dioxide that previously thought. Preliminary data suggest that the ocean’s trenches accumulate large amounts of the greenhouse gas because they trap more organic matter and sediment than other parts of the ocean. The Earth’s oceans absorb large amounts of carbon dioxide. More than 50 percent of the gases emitted into the atmosphere by the burning of fossil fuels is absorbed by ocean water.

Carbon dioxide is absorbed by water and is then dissolved in frigid temperatures near the Arctic and Antarctic. The cold water sinks during the winter, transferring the gas into the deepest layers of the sea. Over a period of hundreds of years, the water once again reaches the surface due to winds and tides. As the water rises near the surface, the carbon dioxide is released back into the atmosphere. Although the cycle is well-understood, scientists have never before been able to measure the levels of carbon in deep sea trenches.

Using new technology, researchers now plan to evaluate the amount of carbon stored in trenches and compare their findings with data from other parts of the ocean. The comparison will illuminate the effects trenches have on climate regulation and increase our understanding of the role they play in the deep sea carbon cycle.