Sunlight, Sea Ice and the Ice Albedo Feedback in Changing Arctic Sea Ice Cover

Some of the greatest observed changes to the rapidly decreasing Arctic ice cover are occurring in the Chukchi and Beaufort Seas, where increased summer ice retreat has created a substantially increased seasonal ice zone. Increased absorption of solar radiation in newly formed areas of open water and the ice albedo feedback have contributed to this decline in the ice cover (Perovich et al., 2007, 2008, 2011). Furthermore, changes in ice type, thickness, ice age, and the timing of melt onset and freezeup may be accelerating this ice albedo feedback. Recent studies have demonstrated substantial increases in solar heat input to the ice-ocean system (Frey et al., 2011; Arrigo et al., 2012) and increased warming of the upper ocean (Steele et al., 2008). These changes in solar radiation distribution affect the heat and mass budgets of this region, determining the nature and character of the ice cover. The overarching goal of this work is to develop a quantitative understanding of the partitioning of solar radiation of the Arctic sea ice cover and its impact on the heat and mass balance of the ice and upper ocean. The central element of our approach is synthesis. We will synthesize remote sensing observations, reanalysis products, field observations, autonomous in situ observations, and process models. Our study area is the Arctic Ocean and surrounding seas, with particular emphasis on the Chukchi and Beaufort Seas. The large-scale analysis will be done on a 25 x 25 km equal area scalable grid. The use of this grid will facilitate integration and synthesis of observations from different datasets and the export of our results to potential users.

No climatology of light transmitted by sea ice exists. Actual measurements are sparse and the light field is subject to many variables: ice thickness, ice age, presence/absence of snow, distribution of absorbing impurities (e.g. chlorophyll, sediment, black carbon), and surface ponding. We plan to address the problem of assessing how much light is transmitted by the ice cover by carrying out radiative transfer modeling. This will permit us to estimate the propagation of shortwave radiation through a spatially complex melting ice cover, as is typically observed in the modern Arctic. We will also use high resolution imagery from previous experiments (Perovich et al., 2002; Perovich et al., 2008) to calculate the spatial distribution of solar radiation reflected, absorbed in the ice, and transmitted to the ocean. In situ observations from field campaigns and autonomous buoys will be assimilated into these calculations. We will also explore the deposition of solar radiation in the water column and its role in the production of the observed near surface temperature maximum (NSTM).

Synthesis of prior studies, in situ measurements, remote observations and radiative transfer modeling will result in a detailed, process-based understanding of the partitioning of solar energy in the Arctic basin, with unique capabilities for comparison and validation in the Chukchi and Beaufort Seas. Collaboration with sea ice modelers will quantify the impact of processes and feedbacks, allowing substantial improvements in regional and basin wide modeling efforts. The magnitude of the role of the ice albedo feedback in ice retreat will be determined. Our well-documented and publicly archived datasets will serve as an important dataset for future model development and validation. In year 3 we will provide near real time information on solar partitioning for use by participants in the Sea Ice Outlook.