accurate sub-seasonal to seasonal prediction remains a major challenge

Newswise – As an indicator and ‘amplifier’ of global climate change, the health and stability of the Arctic is the cornerstone of the stability of our climate system. It has significant impacts on ecosystems, coastal resilience and human settlements in mid and high latitudes.

The Arctic has experienced amplified warming and a significant decline in sea ice in recent decades. On September 15, 2020, the extent of Arctic sea ice (EIS) reached its annual minimum, which, based on data from the National Snow and Ice Data Center, was approximately 3.74 million km2 (1.44 million square miles). This value was about 40% lower than the climate average (~ 6.27 million km2) during the period 1980-2010. It was the second only after the lowest record (3.34 million km2) set on September 16, 2012, but significantly smaller than the second previous low (4.145 million km2, set for September 7, 2016) and third lowest (4.147 million km2, set for September 14, 2007), making 2020 the second lowest SIE year in the satellite era (42 years of data).

In 2020, a total of 39 institutions and organizations around the world submitted their September Pan-Arctic EIS Sea Ice Outlook. From June to August WIS, the median of all forecasts has remained fairly stable (4.33 million km2 in June, 4.36 million km2 in July, and 4.3 million km2 in August), well above the observed value of 3.92 million km2. This indicates that most forecasting systems overestimated the sea ice cover in September 2020.

The precise prediction of the Arctic EIS is still a global problem. Recently a comment posted in Letters of atmospheric and oceanic sciences summarized the forecast from 2009 to 2020 and found that the observed values ​​for most years (8 of 12) were outside the expected interquartile range of dynamic models, indicating that it is still difficult to predict accurately the Arctic HIA on – seasonal timescales (S2S), especially extreme years.

“Studies of sea ice in the Arctic require an improved ability to make more accurate predictions and better understand the physics of sea ice processes,” says Professor Wei, author of this commentary.

In the next step, more effort should be made to assimilate the observations of sea ice, atmosphere and ocean to generate a skillful initialization. Meanwhile, the sea ice forecast relies on a skillful atmospheric model to produce a high-quality atmospheric forecast. Finally, S2S systems should have the ability to capture changes in the properties of sea ice due to global warming, which produces younger and thinner sea ice as well as more melt ponds. Therefore, improved descriptions of sea ice processes in the sea ice model components of forecasting systems are needed.

Global warming is pushing the Arctic to a dangerous tipping point in which irreversible domino-like processes could be triggered. Therefore, it is essential to develop better Arctic sea ice forecasting systems to serve as navigation lights to guide us through this unexplored future climate.

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