Wintertime Transarctic Warm and Moist Air Intrusions Tracked in Present and Future Climate

The Arctic region is strongly impacted by climate change. Poleward transport of warm and moist air is one of the mechanisms contributing to accelerated Arctic wintertime warming. Warm and moist air intrusions (WAIs) into the Arctic are often associated with warm extremes and positive surface energy balance (SEB) anomalies by increased longwave downward radiation (LWD), impacting sea ice extent and recovery. WAIs are expected to increase in frequency in a warming climate until the end of the century, but uncertainties remain regarding their life cycle characteristics, as well as their local impacts and seasonality.

This study focusses on intrusion events that travel from the Greenland and Barents Seas far through the central Arctic. These transarctic WAIs are identified as anomalously high column-integrated water vapor transport (IVT) events and are tracked in space and time with the MOAAP algorithm (Prein et al. 2023).

Focusing on boreal winter (DJF) the occurrence, impacts and life-cycle characteristics of transarctic intrusion events along their path are initially studied using ERA5 data. A first analysis identified 14 transarctic WAIs between 1979-2022, which on average travel 7500 km within a common lifetime of five days. We show that these events are associated with increased integrated water vapor (IWV), LWD, precipitation, and near-surface wind speeds over Arctic sea ice and that these effects become less pronounced towards the end of the WAIs lifecycle. 

Furthermore, we find that during the transarctic WAI’s onset stage in the Greenland and Barents Seas, the associated transport of moist air masses towards the central Arctic is dynamically driven by a strong Icelandic low linked to a positive NAO state or a Scandinavian blocking. As these pressure patterns gradually shift northwards, the WAIs are directed through the Arctic, eventually reaching the Beaufort or East Siberian Seas.

The upcoming analysis will be extended by using data from regional Arctic model simulations with the atmospheric model ICON. Those are forced with ERA5 and two selected global CMIP6 climate models under the SSP370 scenario. The latter represent two distinct Arctic warming scenarios until the end of the century. This allows to assess future changes of transarctic WAIs and their impacts under different future Arctic warming storylines.