Collaborative Research: The Combined Influence of sea ice and snow cover on Northern Hemisphere Atmospheric Climate Variability

Arctic snow and ice form an integral part of the climate system. They have undergone unprecedented changes within the past decade. Initial studies on the potential remote and larger scale influences of their variability have often been inconclusive and even contradictory. In a recent review article, the principal investigators (PIs) of this grant hypothesized that sea ice and snow cover can combine to force large-scale atmospheric variability. This project focuses on analyzing reanalysis datasets and model output from targeted numerical modeling experiments in order to understand the physical pathways linking sea ice and snow cover variability with atmospheric climate variability. This variability may, in turn, influence mid-latitude weather on seasonal time scales. Understanding such processes is anticipated to improve weather prediction on similar time scales, with consequent benefits to the energy, farming, and reinsurance industries, amongst others. The project will contribute to STEM manpower development through providing support for the training of a graduate student, entrainment of undergraduate students into scientific research, and development of a short course of climate prediction. Finally, the project will promote international collaboration with a German research institute. Prescribed sea ice and snow cover perturbation experiments with the Whole Atmosphere Community Climate Model (WACCM) will lead to a quantitative assessment of the physical pathways between sea ice, snow cover and the initiation and maintenance of atmospheric variability, particularly in winter, that cannot be accomplished using statistical analysis alone. The use of a high-top model, which has only recently become available, to study the influence of sea ice and snow cover on the hemispheric winter circulation is novel to this proposal. In parallel, the PIs will collaborate with colleagues running similar experiments with ECHAM6. They will further analyze reanalysis atmospheric data, to test hypotheses about the combined role of sea ice and snow cover in climate variability learned from the model output. The proposed project will analyze the combined impact of sea ice and snow cover anomalies on atmospheric climate variability. This will improve understanding of the atmospheric response associated with changes in sea ice and snow cover, and lead to a quantitative assessment of the links between high-latitude and lower-latitude climates as well as enable improved climate predictions. The proposed research focuses specifically on the combined role of sea ice and snow cover in the initiation and maintenance of the dominant mode of high-latitude atmospheric variability, i.e. the annular mode. Modulation of the annular mode is hypothesized to be a key physical mechanism for climate feedback in high latitudes and is the dominant mode of variability in the mid-latitudes including the industrial centers of the United States, Europe and Asia. The conceptual framework developed in this project will be applied in an operational seasonal forecast model at the end of the project.