Abstract
Abstract. By considering the moisture transport for precipitation (MTP) for a target region to be the moisture that arrives in this region from its major moisture sources and which then results in precipitation in that region, we explore (i) whether the MTP from the main moisture sources for the Arctic region is linked with inter-annual fluctuations in the extent of Arctic sea ice superimposed on its decline and (ii) the role of extreme MTP events in the inter-daily change in the Arctic sea ice extent (SIE) when extreme MTP simultaneously arrives from the four main moisture regions that supply it. The results suggest (1) that ice melting at the scale of inter-annual fluctuations against the trend is favoured by an increase in moisture transport in summer, autumn, and winter and a decrease in spring and, (2) on a daily basis, extreme humidity transport increases the formation of ice in winter and decreases it in spring, summer, and autumn; in these three seasons extreme humidity transport therefore contributes to Arctic sea ice melting. These patterns differ sharply from that linked to the decline on a long-range scale, especially in summer when the opposite trend applies, as ice melt is favoured by a decrease in moisture transport for this season at this scale.
Highlights
If the scientific community were collectively to select an unambiguous indicator of climate change, the long-term decline in the average annual extent of Arctic sea ice (SIE) would undoubtedly be among the most widely proposed
4.1 Patterns of moisture transport for precipitation linked to high-frequency inter-annual fluctuations of the Arctic sea ice extent
These amounts result from averaging the daily values of moisture transport for precipitation (MTP), which allows us to estimate the statistical significance by comparing the daily values of MTP for years with low and high sea ice extent (SIE) using a Student’s t test
Summary
If the scientific community were collectively to select an unambiguous indicator of climate change, the long-term decline in the average annual extent of Arctic sea ice (SIE) would undoubtedly be among the most widely proposed This is not just because of the extreme levels of social concern that this topic generates (IPCC, 2013) in view of all the considerable environmental implications, and because the scientific complexity of this field of study covers a very broad spectrum of disciplines. In this article we complement our previous study by (i) focusing on the pattern of MTP linked to high-frequency interannual variability as characterised by years with low or high SIE set against its long-term decline and (ii) analysing the role of extreme MTP events in the Arctic SIE by investigating what happens to the daily march of the Arctic sea ice extent when extreme MTP transport periods from the four main sources of humidity for the Arctic coincide. As in Gimeno-Sotelo et al (2018), we compared these results with computations of vertical integrated moisture flux (VIMF) and with an analysis of changes of the frequency of occurrence of the atmospheric circulation types responsible for changes in moisture transport
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