Dynamic and thermodynamic processes affecting atmospheric moisture transport to the Arctic during the ARTofMELT expedition in spring 2023

Abstract. Moisture transport substantially affects the surface energy budget in the Arctic, primarily through its effect on cloud formation. Increased cloudiness enhances downward longwave radiation, which advances the spring onset of snow melt on top of sea ice. The ARTofMELT expedition, conducted in the Fram Strait in May to early June 2023, aimed to improve understanding of the processes governing melt onset, which in that spring occurred unexpectedly late. We analysed large- and synoptic-scale atmospheric circulation patterns affecting moisture transport, being responsible for the dry and cold conditions observed in the Fram Strait. During the first half of the expedition, several cyclones travelled from the Icelandic region towards Svalbard, but most of the associated moisture transport was directed to the Barents Sea rather than the Fram Strait. This was a consequence of cyclone tracks being steered by a southwest-northeast oriented jet stream, which was linked to enhanced baroclinicity, driven by an anomalously warm Norwegian-Barents Sea region and a cold airmass near the North Pole. During the second half of the expedition, conditions in the Fram Strait were dominated by northerly flow, which sustained dry conditions and temperatures mainly below freezing point, except of the last four days. On these days, the large-scale circulation resembled that of the first half of the expedition, however, the flow had a stronger meridional component, and baroclinicity near the Fram Strait was weaker. Our result indicated that adiabatic lifting along frontal zones was the primary mechanism for water vapour removal, particularly under baroclinic conditions.