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Reduced ocean circulation during ice age increased carbon storage in the deep sea by Staff Writers Bremen, Germany (SPX) Dec 09, 2021
As a natural sink for carbon, the ocean is a central element of the Earth's climate system. The amount of carbon removed from the system in the long run depends on how much particles containing carbon are stored in the seabed. Here, the availability of dissolved oxygen is of central importance, as it is consumed during the microbial decomposition of previously formed biomass. The distribution of oxygen in the water column is primarily determined by the vertical circulation. To answer the question of whether the corresponding conditions in the deep ocean were subject to changes in the recent history of the Earth, the authors of the new study examined sediment samples. Chemical elements that can be used as indicators for oxygen-free conditions and are preserved in the sediment over thousands to millions of years were analyzed.
Sediment cores from biologically highly productive area analyzed Sinking particles of dead organic material is processed by microorganisms in the water column, as well as on the seabed. This process mostly consumes oxygen. If large amounts of organic material sink, this can require more oxygen than is supplied by the ocean currents. The water column becomes "anoxic", which means oxygen-free.
Oxygen deficiency also detected in the deep-sea during ice age "What is new about the current study is that the depletion of oxygen is not limited to water depths of a few hundred to a thousand meters but has now also been detected at the bottom of the ocean", says co-author Dr. Matthias Zabel from MARUM.
More organic carbon stored at depth "Today, oxygen-free zones are found on the shallow shelf up to a water depth of a few hundred meters, that is at the transition from the continental shelf to the open ocean. During the Ice Age, on the other hand, the water of the open ocean was anoxic at greater depths", emphasizes Dr Florian Scholz. The GEOMAR biogeochemist is co-author of the study and head of the Emmy Noether research group ICONOX - Iron cycling in continental margin sediments and the nutrient and oxygen balance of the ocean.
Implications for the global carbon cycle "Against the background of the anthropogenic CO2 increase current climate change, it is crucial to determine and evaluate processes and mechanisms that impact the oceanic bottom water oxygen content", the paper states.
Research Report: "Persistent deep water anoxia in the eastern South Atlantic during the last ice age"
Melting glaciers may create new Pacific salmon habitat, study finds Washington DC (UPI) Dec 7, 2021 Melting glaciers may produce thousands of miles of new Pacific salmon habitat, a study published Tuesday by Nature Communications found. As glaciers in the mountains of western North America melt, or retreat, they could produce around 4,000 miles of new Pacific salmon habitat by the year 2100, the data showed. After modeling glacier retreat under different climate change scenarios, the glaciers could reveal potential new Pacific salmon habitat nearly equal to the length of the Mississipp ... read more
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