| Description |
Arctic sea ice is a key component of the climate system, acting as a reflective barrier between the ocean and the atmosphere. The decrease in sea ice over the observational record is associated with several feedback processes, such as the ice-albedo feedback. Here, general sea ice-atmosphere feedback (SAF) is defined in which a sea ice anomaly causes surface and tmospheric responses that either enhance the initial anomaly (positive feedback) or oppose the initial anomaly (negative feedback). Chapters 2 and 3 examine the local SAF over the Barents Sea in an uncoupled modeling framework. Results indicate that the SAF is positive and dominated by the thermodynamic component of the feedback, where anomalously high sea ice cover over the Barents sea favors additional ice growth because it decreases upward surface turbulent heat fluxes, leading to atmospheric cooling and reduced downwelling longwave radiation flux at the surface, while the opposite scenario occurs for anomalously low sea ice cover. Chapter 4 studies the effect of suppressing the SAF in a coupled model by exposing the atmosphere over the Barents Sea to surface turbulent heat fluxes, longwave heat fluxes, and surface temperatures weighted by climatological sea ice cover. Variability in sea ice, atmospheric temperature, and sea surface temperature decrease in response to SAF suppression, indicating that the coupled feedback over the Barents Sea is positive. While thermodynamic processes play a large role in regional sea ice-atmosphere interactions, wind-driven sea ice transport controls the overall Arctic ice mass on annual-and-shorter time scales. Most sea ice is exported from the Arctic through the Fram Strait, and changes in sea ice export are linked to hemispheric-scale atmospheric variability. In Chapter 5, the leading propagating patterns of variability associated with Fram Strait sea ice flux (F) are determined by applying Hilbert empirical orthogonal function analysis to reanalysis data. The leading two surface wind patterns are correlated with F when cyclonic and anticyclonic circulation features are positioned downstream and upstream of the Fram Strait, enhancing the northerly component of the flow through the Strait. |
