Atmospheric rivers are known from different parts of our planet; however their impact might be even more important in the polar regions. They are described as long and concentrated “flowing belts” of water vapor in the atmosphere. This transported moisture may have originated from different regions, but the extratropical cyclones play an important role in their formation. And such atmospheric rivers can be extremely big and can carry the amount of vapor compared to the water of a big river. When they reach land, atmospheric masses rise and release water in the form of landfalls, usually snow or rain.
Researchers use various tools to study atmospheric rivers, they include aerial observations, radars, satellites, etc. Also, scientists work on data collection on atmospheric rivers to better understand weather and climate patterns, and be able to create models and make predictions. Before it was believed that atmospheric rivers usually impact regions between the tropics and the poles, however nowadays observations indicate direct impact on the polar regions as well.
Impact on the polar regions
According to scientific observations, atmospheric rivers are becoming more frequent in the cold areas. Thus, poleward moisture transport is linked to the repeated influx of cyclones into the Arctic region, where regional hydrological events are impacted. Also, with changing climate and appearing extreme weather conditions, the amount of incoming vapor within atmospheric rivers is projected to increase.
Recent data shows that increasing extreme melt in northeast Greenland is most likely driven by the atmospheric rivers. Interestingly, in this area near low-elevation outlet glaciers, 50–75% of extreme melt occurs under the effect of atmospheric rivers. Together with winds, atmospheric rivers contribute to increasing moisture content in the area as a result of climate change.
Another negative impact of atmospheric rivers in the North is linked to the reduced recovery of sea ice. It seems like atmospheric rivers bring more warmth from lower latitudes into the Arctic, even in winter time. It is shown that in the Barents-Kara Sea and Central Arctic this effect may account for up to 34% of the sea-ice cover decline. In addition, atmospheric rivers, for example Siberian atmospheric rivers, can upglide cold air areas over sea ice and, as a result, heat different layers of the sky (see image). These events impact the Arctic region – the sea ice and the marine ecosystems.
Antarctica seems to be not that much isolated and protected from the impact of the atmospheric rivers as well. It is believed that atmospheric rivers have the same negative impact (as in the Arctic) on sea ice in the Southern Ocean, however the genesis of this phenomenon is not frequent with low inland penetration in the south. However, on West Antarctica they have a double impact – both precipitation (snowfalls) and surface melting. In this part of the area, they cause intense precipitation in short periods of time and account for 11 % of the annual surface accumulation. According to the 2019 satellite data, in West Antarctica, up to 41% of height growth were due to several extreme precipitation events, including landfalling atmospheric rivers. Atmospheric rivers as subtropical moisture sources can cause an anomalously high snow accumulation in East Antarctica, which is important for understanding trends of the total Antarctic ice sheet and the impact of climate change on it. Also, atmospheric rivers together with wind events may contribute to extremely dry climate of the East Antarctic, intense snowfall sublimation can lead to almost no precipitation at the ground there.
Role in understanding global processes
Atmospheric rivers seem to be a keystone element in the global water cycle, and they play a significant role in many natural processes on the way from locations of their origins to polar regions. Recent findings show how wide the spectrum of their impact on the local weather conditions and precipitation can be. The phenomenon of atmospheric rivers is not fully understood, however, the current knowledge allows the development of application areas. Among the significant opportunities are evaluation of climate change projections and analysis of extreme global events. The polar regions are more frequently hit by atmospheric rivers causing new extreme events in these remote destinations. To develop accurate climate projections and to improve forecasting capabilities, scientists need to collect more data on atmospheric rivers, especially in the areas with minimum human impact, like in the polar regions.
Dr. Ekaterina Uryupova is a Senior Fellow at the Arctic Institute. She has been working in the polar regions as a researcher and a polar guide. Her areas of expertise revolve around climate change, marine ecosystems, fisheries, and environmental policy.
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