Atmospheric rivers over the Arctic: lagrangian characterization of moisture sources

In recent years, the Arctic has been a subject of special interest due to the drastic effect of climate change over the region. Despite there are several mechanisms that influence the Arctic región, recently some studies have suggested the influence of moisture transport in the observed sea ice loss. Moisture transport can affect the region in different ways: direct precipitation over the región, the radiative effect from the cloud cover and latent heat release. Atmospheric rivers (ARs) represent one of the main mechanisms of global moisture transport and despite have been shown especially relevant to the link between lower and higher latitudes, its effect over the Arctic has not been deeply investigated. The aim of this work is to establish the groundwork for future studies about the effect of AR over the Arctic region linked to moisture transport. For this purpose, an automated algorithm was used to identify regions of maximum ARs occurrence over the Arctic analysing the number of ARs detections for every month over a band of 10° of latitude centered on 60°N. The lagrangian model FLEXPART was used to analyze the areas that provide moisture to the located areas, and therefore to the ARs. Using this model, the anomalous moisture contribution to this meteorological structures was analyzed taking into account only the dates of ARs occurrence. From the results, main moisture sources for ARs events extends over the North Atlantic and North Pacific oceans, moreover, the local input of moisture over the region of maximum ARs occurrence seems to be especially relevant. In general terms, moisture comes from major evaporative areas over the western part of the oceanic regions on the band between 30ºN and 40ºN for most of the months in the year, ahowing a continental origin in the summer month. This behavior agrees with the climatological moisture transport into the Arctic addressed by previous studies. However, especially associated with ARs event an intensification of local moisture uptake over the area of maximum ARs occurrence and its surroundings occurs. The study of the origin of moisture for Arctic ARs is an important step in the analysis of the effect of these structures on the Arctic environment. Further analysis regarding the contribution of moisture from ARs over the region should be conducted in order to complete the analysis on the relation ARs-sea ice; being this study suitable for a future work.