Impact of an abrupt Arctic sea ice loss on the extreme precipitation events in the midlatitudes
Authors: Delhaye Steve , Fichefet Thierry , Massonnet François , Docquier David , Chripko Svenya , Keeley Sarah , Msadek Rym , Roberts Christopher 
Published: March 2020

&lt;p&gt;&lt;span&gt;The current &lt;/span&gt;&lt;span&gt;Arctic &lt;/span&gt;&lt;span&gt;sea ice &lt;/span&gt;&lt;span&gt;melting is accompanied by a &lt;/span&gt;&lt;span&gt;significant&lt;/span&gt;&lt;span&gt; Arctic warming, which &lt;/span&gt;&lt;span&gt;could &lt;/span&gt;&lt;span&gt;induce several climatic responses not limited to the high latitudes. &lt;/span&gt;&lt;span&gt;These responses include&lt;/span&gt;&lt;span&gt; change&lt;/span&gt;&lt;span&gt;s&lt;/span&gt;&lt;span&gt; in &lt;/span&gt;&lt;span&gt;storm tracks&lt;/span&gt;&lt;span&gt;, &lt;/span&gt;&lt;span&gt;modification of&lt;/span&gt;&lt;span&gt; the &lt;/span&gt;&lt;span&gt;jet stream patterns&lt;/span&gt;&lt;span&gt; as well as a stimulation of the planetary waves. The objective of this &lt;/span&gt;&lt;span&gt;study&lt;/span&gt;&lt;span&gt; is to determine the &lt;/span&gt;&lt;span&gt;short-term &lt;/span&gt;&lt;span&gt;changes &lt;/span&gt;&lt;span&gt;on the extreme precipitation events&lt;/span&gt;&lt;span&gt; over the&lt;/span&gt; &lt;span&gt;high and mid-latitude&lt;/span&gt;&lt;span&gt;s&lt;/span&gt; &lt;span&gt;due to a sudden &lt;/span&gt;&lt;span&gt;loss&lt;/span&gt;&lt;span&gt; of Arctic sea ice. These changes &lt;/span&gt;&lt;span&gt;are&lt;/span&gt; &lt;span&gt;analysed&lt;/span&gt;&lt;span&gt; using &lt;/span&gt;&lt;span&gt;t&lt;/span&gt;&lt;span&gt;wo&lt;/span&gt; &lt;span&gt;different &lt;/span&gt;&lt;span&gt;climate models &lt;/span&gt;&lt;span&gt;(&lt;/span&gt;&lt;span&gt;ECMWF-IFS &lt;/span&gt;&lt;span&gt;and CNRM-CM6)&lt;/span&gt; &lt;span&gt;at two different horizontal resolutions, &lt;/span&gt;&lt;span&gt;that participate to the EU&lt;/span&gt;&lt;span&gt; Horizon 2020 PRIMAVERA &lt;/span&gt;&lt;span&gt;project. &lt;/span&gt;&lt;span&gt;A common protocol in which the sea ice albedo is reduced to the ocean value is applied &lt;/span&gt;&lt;span&gt;to simulate the sudden loss of Arctic sea ice. &lt;/span&gt;&lt;span&gt;The&lt;/span&gt;&lt;span&gt; results show a&lt;/span&gt;&lt;span&gt;n increase&lt;/span&gt; &lt;span&gt;in&lt;/span&gt;&lt;span&gt; drought &lt;/span&gt;&lt;span&gt;duration &lt;/span&gt;&lt;span&gt;in &lt;/span&gt;&lt;span&gt;early &lt;/span&gt;&lt;span&gt;winter&lt;/span&gt; &lt;span&gt;over&lt;/span&gt;&lt;span&gt; the &lt;/span&gt;&lt;span&gt;south&lt;/span&gt;&lt;span&gt;western &lt;/span&gt;&lt;span&gt;North America&lt;/span&gt; &lt;span&gt;in the ECMWF-IFS model at &lt;/span&gt;&lt;span&gt;the &lt;/span&gt;&lt;span&gt;two different horizontal resolution&lt;/span&gt;&lt;span&gt;s &lt;/span&gt;&lt;span&gt;and in the CNRM-CM6 at low resolution, &lt;/span&gt;&lt;span&gt;and over the western part of the Mediterranean Basin in the ECMWF-IFS model&lt;/span&gt;&lt;span&gt;. T&lt;/span&gt;&lt;span&gt;his increase can be understood by a stationary wave response due to Arctic sea ice loss which leads to &lt;/span&gt;&lt;span&gt;an amplification of the subsidence over these two regions. &lt;/span&gt;&lt;span&gt;Indeed, a&lt;/span&gt;&lt;span&gt; northward shift of the North &lt;/span&gt;&lt;span&gt;Atlantic&lt;/span&gt;&lt;span&gt; High and North &lt;/span&gt;&lt;span&gt;Pacific&lt;/span&gt;&lt;span&gt; High &lt;/span&gt;&lt;span&gt;is modelled &lt;/span&gt;&lt;span&gt;in &lt;/span&gt;&lt;span&gt;early &lt;/span&gt;&lt;span&gt;winter. &lt;/span&gt;&lt;span&gt;Thanks to these results, a&lt;/span&gt;&lt;span&gt;brupt Arctic sea ice loss seems to play a role on the extreme precipitation events over mid-latitude&lt;/span&gt;&lt;span&gt;s&lt;/span&gt;&lt;span&gt;.&lt;/span&gt;&lt;/p&gt;