Arctic sea ice: satellite observations, global climate model performance, and future scenarios

Thesis (M.S.) University of Alaska Fairbanks, 2011This thesis examined Arctic sea ice trends through observational records and model-derived scenarios. A regional analysis of Arctic sea ice observations 1980-2008 identified regional trends similar to the pan-Arctic. However, winter maximum (March) extent in the Atlantic quadrant declined faster. Through an analysis of Atlantic Ocean temperatures and Arctic winds, we concluded that melting sea ice extent may result in increased Atlantic Ocean temperatures, which feeds back to further reductions in Atlantic quadrant extent. Further, Arctic winds do not appear to drive Atlantic ice extent. We evaluated performance of 13 Global Climate Models, reviewing retrospective (1980-2008) sea ice simulations and used three metrics to compare with the observational record. We examined and ranked models at the pan-Arctic domain and regional quadrants, synthesizing model performance across several Arctic studies. The top performing models were able to better capture pan-Arctic trends and regional variability. Using the best performing models, we analyzed future sea ice projections across key access routes in the Arctic and found likely reduced ice coverage through 2100, allowing increasingly longer marine operations. This unique assessment found the Northwest and Northeast Passages to hold potential for future marine access to the Arctic, including shipping and resource development opportunities.University of Alaska, Fairbanks’ International Arctic Research Center, National Science Foundation’s Office of Polar Programs, Scenarios Network for Alaska and Arctic Planning1. Regional variations in Arctic sea ice extent and the role of winds and ocean temperatures -- 2. An evaluation of global climate models: Arctic sea ice extent -- 3. Future Arctic sea ice dynamics and implications for marine access -- Appendix 3.1 -- Conclusions -- References

An evaluation of sea ice deformation and its spatial characteristics from the regional arctic system model

The Regional Arctic System Model (RASM) is used to investigate the process and frequency of extreme sea ice shear deformation events resulting in pycnocline upwelling due to Ekman pumping as described in McPhee et al. (2005). RASM is a fully coupled land, atmosphere, sea ice, and ocean model with high spatial and temporal resolution. Time series analysis of the upper ocean temperature structure, basal melt rate, total deformation rate, and ice-ocean stress curl yield the identification of individual events. Shear deformation events generate an upper ocean response given a positive ice-ocean stress curl, i.e., induced by counterclockwise rotation in the ice velocity field relative to the underlying ocean. Spatial and temporal characterization of the total deformation rate indicates that fine spatial and temporal resolution, on a statistical scale, is important for the energy budget of the Arctic. Results demonstrate a power law relationship between the mean deformation rate and length scale. This is hypothesized as being due to RASMs fully coupled system allowing for naturally occurring high frequency noise and the cascade of energy among model components. Simulated events are infrequent their relative impact on large scale energy exchange remains undetermined, which warrants further research of these phenomena.http://archive.org/details/anevaluationofse1094527872Lieutenant, United States NavyApproved for public release; distribution is unlimited