Movie:Open water days in 21st century
Information Page: Open water days in 21st century
Sea ice free days over the 21st century
|Keywords:||Community Earth System Model|
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Statement: open water days in the 21st century
Abstract: Expansion of Sea Ice Free Days from 1920-2100
Sea ice covers large regions of the Arctic Ocean. At present, the northernmost waters remains frozen all year, in other regions seawater freezes every year when temperatures drop in October-November, and the sea ice thaws again when solar radiation is intense and long days prevail in the early summer. This sea ice dataset shows how long the ‘open water season’ lasts for any location in the Arctic region. The duration of open water is relevant for ecosystem and coastal processes, and human activities such as shipping, industrial development, fishing and indigenous mammal hunting.
Maps of the open water season over 1920-2100 are calculated averaging output of 30 simulations of the Community Earth System Model (CESM). This climate model describes the physical processes of the atmosphere, ocean, land surface and sea ice and their interactions. For historical times, 1920-2005 in this specific case, the model can be forced by real-world observations of incoming solar radiation and concentrations of greenhouse gasses and aerosols. For the future, 2005-2100, a scenario has to be chosen; scientists have precisely defined a suite of different scenarios called ‘Representative Concentration Pathways’. The model simulations analyzed here used the ‘RCP 8.5’ scenario, which assumes that greenhouse gas emissions continue to rise throughout the 21st century.
Sea ice can be seen to cover large parts of the Arctic in the mid-20th century. For example, at that time the open water season is as short as 2 month along the Alaskan and Siberian coasts. Other parts of the Arctic Ocean remain frozen all year, such as the Canadian Archipelago, where explorers stranded in the ice many times. Over the duration of the simulation global warming causes the open water season to vastly expand. The retreat of sea ice has started already in the late 20th century, and scientists have observed with satellites the expansion of the open water season over the last 35 years. The model predicts that by 2050, the entire Arctic coastal region will experience 60 additional days of ice-free conditions.
A longer open water season triggers coastal change, because longer exposure to waves and storm surges cause erosion of the Arctic permafrost coast. Acceleration of erosion and coastal flooding is to be expected with the expansion of the open water season. Coastal villages in Arctic Alaska may need to be better protected or relocated in the future.
Barnhart, K., Miller, C.R., Overeem, I., Kay. J., 2015. Mapping the future expansion of Arctic open water. Nature Climate Change. 2 November 2015.
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