MERGE SP: ARTofMELT Arctic Ocean icebreaker expedition 2023

The Arctic is warming at a rate at least twice as fast as globally. There are multiple reasons for this, but they are not yet fully understood, let alone quantifiable. It is nevertheless evident that multiple feedback mechanisms are active, such as the melting of Arctic Ocean pack ice and the warming this will cause when white snow and ice is replaced by dark open water. Clouds are very important for the energy balance over the Arctic Ocean and pack ice. Cloud droplet and ice crystal are formed on aerosol particles, which is why ARTofMELT has an extensive program for aerosol and cloud observations.

The international icebreaker expedition ARTofMELT to the Arctic between 7 May – 15 June 2023 takes place in the abrupt transition between winter and spring in the Arctic and enables studies of the processes and mechanisms that govern the melting of the Arctic ice sheet. A special focus is on the inflow of warm air up to the Arctic, which is believed to have a major impact on the actual start of melting and thus also how the pack ice develops throughout the Arctic summer (Dada et al, 2022). The frequency and intensity of warm and moist air-mass intrusions into the Arctic have increased over the
past decades and have been related to sea ice melt. Although the start of the melting is necessary to understand in order to predict future climate change, the underlying processes are rarely studied, largely due to the difficult conditions prevailing in the Arctic at this time of year.

PURPOSE AND AIM
The purpose of this short project is to enable evaluation and quality-control data from the ARTofMELT (Atmospheric rivers and the onset of sea ice melt) Oden icebreaker expedition to the Arctic Ocean in early summer 2023. The specific data in question were acquired by two aerosol instruments. The instruments in question are (i) our Single-Particle Soot
Photometer (SP2) and (ii) our Cloud Condensation Nuclei Counter (CCNC).
The overarching scientific objective of the ARTofMELT expedition is to
• study how intrusions of warm and moist air-masses into the Arctic in spring affect the onset of pack ice melting and its repercussions on Arctic climate change.
The specific scientific objectives of the Lund University contribution to ARTofMELT are to:
• quantify the contribution of light-absorbing soot particles to the Arctic Ocean cloud and ice population during warm air intrusions, and contrast these to periods with clean Arctic air;
• quantify the concentrations of cloud condensation nuclei during periods of warm air intrusions and clean Arctic air and compare with parallel observations inside low-level Arctic clouds.