A warmer Arctic Ocean leads to more snowfall farther south, new model says

A warmer Arctic Ocean leads to more snowfall farther south, new model says

An increasingly warm and ice-free Arctic Ocean has led to more moisture at higher latitudes in recent decades. This moisture is transported south by cyclonic weather systems, where it precipitates as snow, affecting the global hydrological cycle and many dependent terrestrial systems (Illustration: Tomonori Sato). Photo credit: Tomonori Sato

A new model explains that water evaporating from the Arctic Ocean due to a warming climate is transported south and can lead to increased snowfall in northern Eurasia in late autumn and early winter. This information enables more accurate predictions of severe weather events.

Rising air temperatures due to global warming are causing glaciers and polar ice caps to melt. Seemingly paradoxically, snow cover has increased in some areas of northern Eurasia in recent decades. However, snow is a form of water; Global warming increases the amount of moisture in the atmosphere, and with it the amount and likelihood of rain and snow. Understanding where exactly the moisture comes from, how it is produced and how it is transported south is relevant for better forecasting of extreme weather and climate development.

University of Hokkaido environmental scientist Tomonori Sato and his team developed a new, labeled moisture transport model based on the “Japanese 55-year reanalysis dataset,” a careful reanalysis of worldwide historical weather data spanning the past 55 years. With this material, the group kept their model calibrated over much longer distances than before, and in particular were able to elucidate the mechanism of moisture transport across the huge land masses of Siberia.

A technical standard for analyzing wicking is the “tagged wicking model”. This is a computer modeling technique that tracks where hypothetical chunks of atmospheric moisture form, how they move around, and where they fall due to local climatic conditions. But as the distance from the ocean increases, the computer models become increasingly inaccurate. This makes it particularly difficult to make quantitative predictions. Therefore, these methods could not satisfactorily explain snowfall in northern Eurasia.

The results of the study published in the journal npj Climate and Atmospheric Science show that water evaporation from the Arctic Ocean has increased over the past four decades and that the largest changes occurred in the Barents and Kara Seas north of western Siberia and over the Chukchi and East Siberian Seas north of eastern Siberia in October and December. At this time of year, the Arctic Ocean is still warm and the area not covered by ice is still large.

Importantly, this trend coincides with the area where sea ice loss was most severe over the study time frame. In addition, the quantitative model shows that evaporation and snowfall are particularly strong during certain weather events such as cyclone systems, which absorb and transport unusually large amounts of moisture southwards as far as Siberia, also providing detailed and specific mechanistic insights into the region’s weather dynamics.

Because the Arctic Ocean is twice as sensitive to rapid warming as the global average, evaporation and resulting changes in the water cycle over northern Eurasia will be even more pronounced in the coming years.

The researchers say that since snowfall often delays the downstream effects of the abnormal weather events that cause it, “knowledge of the precursor signal stored as a snow cover anomaly is likely to help improve seasonal forecasts of abnormal weather, e.g. B. The potential for heat waves that increases the risk of fire in boreal forests.”

Thus, this study provides a key element to understand the mechanism of this and other weather systems influenced by it and thus to be able to better predict serious events that could damage people and infrastructure.

More information:
Tomonori Sato et al., Enhanced Arctic wicking towards Siberia in autumn revealed by a model experiment with labeled wicking, npj Climate and Atmospheric Science (2022). DOI: 10.1038/s41612-022-00310-1

Provided by the University of Hokkaido

Quote: Warmer Arctic Ocean leads to more snowfall farther south, according to new model (2022, November 24), retrieved November 24, 2022 from https://phys.org/news/2022-11-warmer-arctic-ocean- snowfall-south .html

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