Polar2MidLat · Polar-to-mid-latitude climate linkage effects on cold air outbreaks

Polar-to-mid-latitude climate linkage effects on cold air outbreaks

The climate of the polar regions has changed dramatically during the past decades, and as the globe continues to warm is it expected to change even further. Over the Northern Hemisphere, the largest manifestation of global warming at high latitudes has been in the form of a significant reduction in sea ice cover. This change from sea ice to liquid water has at the same time fostered a number of local and regional feedbacks in the form of an excessive amount of surface warming over the polar cap, in a phenomenon usually called “Arctic amplification” (AA). In this project, our aim was to address the role of a warming Arctic on the climate of the mid-latitudes. In particular, our focus was the climate of Europe and the changes in the frequency of cold snaps under reduced sea ice. Another focus was on a potential linkage between sea ice changes and the pathways and frequency of cut-off lows (COLs) affecting southern Europe. COLs are mid-tropospheric cyclonic perturbations that usually explain a significant portion of the annual precipitation, particularly over the Mediterranean Sea region. Therefore, any changes to such systems could have an impact on the availability of drinking water and on the risk of flooding, among others. The main results from our project have shown that the alteration caused from sea ice loss to the atmospheric circulation of the Northern Hemisphere (via north-south migrations of the storm tracks and upper-level jet) has a significant impact on the onset of winter blocking over central and northern Europe, which are crucial for the advection of cold polar air into mid-latitudes. At the same time, the latitudinal shift of the jet is capable of modifying the pathways of COLs reaching the Mediterranean Sea: under reduced sea ice over the Arctic, there are less COLs reaching the western Mediterranean, which most clearly impact the Iberian Peninsula where a significant decrease in total and extreme precipitation is obtained. These results are of particular relevance, given that they might bring light into the underlying mechanisms sustaining the recent decline in precipitation over parts of eastern and southern Spain in recent years.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз