Low-level temperature inversions over the Marginal Ice Zone (MIZ) during the Arctic Pacific summer melting season are heavily impacted by intensified sea ice melt. Here, we developed a high-resolution model for the Arctic Pacific sector using the polar-optimized Weather Research and Forecasting (PWRF) model and applied it to simulate the lower atmosphere during the 2018 Chinese National Arctic Research Expedition (CHINARE 2018). Model outputs, combined with observational data, were used to investigate extreme variations in temperature inversions over the MIZ. We evaluated three planetary boundary layer (PBL) schemes (MYJ, MYNN, and YSU) and found that the MYJ scheme best reproduced the lower atmospheric characteristics during the return voyage of CHINARE 2018, accurately simulating the position and intensity of a mesoscale cyclone event. Analysis of 83 observed temperature inversions showed that inversion variability increased significantly following the cyclone’s passage, with a general weakening of inversion strength, except over the MIZ where it intensified. Atmospheric temperature diagnostics using PWRF model outputs revealed that accelerated sea ice melt enhanced surface radiative cooling, increasing near-surface inversion strength. Enhanced turbulent mixing triggered convection, leading to the temporary disappearance of near-surface inversions, but they reappeared as convective clouds gradually formed. Intensifying cloud-top cooling subsequently strengthened cloud-top inversions. The transportation of high convective available potential energy and water vapor into the MIZ provided sufficient energy and moisture for convection. The intensification of sea ice melting ultimately triggered convective processes, resulting in extreme temperature variations over the MIZ.

Low-Level temperature inversions,Marginal ice zone,Intensified sea ice melting,Surface radiative cooling,Cloud-top cooling,Energy and moisture,Convective