Geoscience Reference
In-Depth Information
6
Precipitation, Net Precipitation, and River
Discharge
Overview
One of the keys to understanding the Arctic climate system is the
determination of freshwater transfers. As introduced in
Chapter 2
, the
Arctic Ocean is characterized by a fairly fresh surface layer, primarily
maintained by river discharge, the import of low salinity seawater through
the Bering Strait, and net precipitation over the Ocean itself. This fresh
surface layer allows sea ice to readily form. In turn, the major exports
of freshwater are the ice and water fluxes to the North Atlantic through
the Fram Strait and through the Canadian Arctic Archipelago. Following
the water through the atmospheric, terrestrial, and oceanic branches of
the Arctic hydrologic cycle, and assessing links between these fluxes,
freshwater storages, and the global climate system is a vibrant area of
research. But the problem cannot be tackled all at once. Here, the focus
is on a large, yet digestible piece - precipitation, net precipitation, and
river discharge to the Arctic Ocean. Aspects of the ocean branch will be
examined as part of
Chapter 7
.
Precipitation is a difficult quantity to accurately measure in the Arctic.
Evapotranspiration is even more difficult to obtain. Although annual
average precipitation totals over the Arctic range widely, there is also
strong seasonality. Precipitation over the Atlantic sector exhibits a general
maximum during the winter half of the year, whereas elsewhere a warm
season maximum is the rule. Annual net precipitation (precipitation less
evapotranspiration, which can be assessed from atmospheric reanalysis
data) is typically 150-300 mm over land, 150-200 mm over the
central Arctic Ocean and more than 1,000 mm near the Icelandic Low.
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