Pan-Arctic climate and ecosystem response to historical and projected changes in the seasonality of sea ice melt and growth

PI: Bonnie Light, co-I: Don Perovich and Marika Holland

Intellectual merit: Arctic sea ice has undergone dramatic change in recent years, with a well documented retreat of the summer ice cover and a transition to a younger, thinner and more vulnerable ice pack. Climate models project that these changes will accelerate in the future and that a transition to ice-free summers is possible later this century. These changes in the state of the ice cover are intricately linked to changes in the annual cycle of sea ice growth and decay, which in turn is strongly affected by the seasonal timing of key events such as the initiation of fall freezeup, onset of summer melt, and accumulation of snow. Behavior of the Arctic marine ecosystem and biogeochemical cycling are also sensitive to the seasonal timing of these events and the summertime sea ice distributions.
We propose to carry out quantitative assessment of the drivers, effects, and ramifications of the seasonal timing of sea ice melt onset and freeze initiation over the observational record and using earth system model projections of future climate. We will synthesize existing datasets including results from ARCSS Synthesis of Arctic System Science (SASS) and Arctic Observing Network (AON) projects. We will use sensitivity integrations from the Community Climate System Model, version 4 (CCSM4), which has improved polar processes and capabilities, including a more general and consistent sea ice albedo representation and an ecosystem/biogeochemistry component. Our study will 1) investigate interactions and feedbacks between seasonal changes in the sea ice and snow conditions, the amount of solar insolation, and the partitioning of this radiation, 2) assess the implications of these interactions for changes in ice-ocean-atmosphere heat and freshwater exchange and their influence on ecosystem dynamics, biogeochemical cycling, and climate in the CCSM, and 3) evaluate and ultimately improve the capabilities of earth system models in light of these processes, specifically by improving the physics associated with surface albedo and light transmission parameterizations for ice covered seas. We will also investigate the role of sea ice advection of iron as a driver of Arctic biogeochemistry.

Broader impacts: The results of this work will be used to draw critical assessments for the representation of the seasonal cycle of Arctic climate and the Arctic ecosystem in earth system models. The work will aid in understanding the intricate balance of key trigger events in the Arctic atmosphere-sea ice-ocean-biogeochemical system. Our results will be useful to ecosystem models that include higher trophic levels, as well as to researchers designing and analyzing observational field programs. Through the pan-Arctic and global domains of coupled model runs, context will be formulated for finite geographical measurements.
The training of students in academic and non-academic environments will also be a focus of this project. Through mentoring programs at NCAR and CRREL a graduate and two undergraduate students will work on the project. Results from this work will also be entrained in the classroom through visits to local elementary schools, and curricula at the University of California, Irvine and the University of Washington. Museum presentations at the Pacific Science Center (Seattle), the Burke Museum (UW) and the Montshire Musuem (Vermont) will reach wider audiences outside of the traditional classroom.