Evolution of sea ice radiometric properties during melt and breakup

Abstract:

In polar regions, sea ice is a crucial mediator of the interaction between earth's atmosphere and oceans. Its formation and breakup is intimately connected with local weather patterns and larger-scale climatic processes. Sea ice undergoes rapid change during Spring melt and breakup, during which areas transition from ice-covered to ice-free in a matter of weeks. This has a profound impact on the use of these regions by local Indigenous populations, where activities such as hunting and fishing are central to community livelihood. In order to investigate the physical phenomena at the heart of this problem, a set of targeted, intensive observations were made over the course of two Spring melt and breakup periods in Kotzebue Sound, Alaska. These were performed using high-endurance, fixed-wing unmanned aerial vehicles (UAVs) containing custom-built scientific payloads. We present on the results of these measurements, describing the variation of sea ice radiometric properties including spectral reflectance, broadband shortwave albedo, and net longwave radiation. These measurements are considered alongside observations of the flux of momentum and heat between the sea ice surface and the marine-atmospheric boundary layer (MABL). Repeated flights over the measurement period captured the full transition in sea ice from a white, snow-covered state to a broken up, ponded state. This program is part of the Ikaaġvik Sikukun project, a collaborative effort in which an Indigenous Elder advisory council from Kotzebue and scientists participated in co-production of hypotheses and observational research.