The Earth's sea ice cover is a mosaic of individual pieces of ice, known as floes, with length scales that range from several meters to tens of kilometers. Yet the influence of lateral sizes on the evolution of sea ice and climate has been poorly studied, as the effect of the size of sea-ice floes on sea-ice melting is normally formulated in terms of the ratio between side and basal floe area, only important for floes smaller than about 30 meters. I'll discuss efforts to model the evolution of the distribution of floes, and demonstrate that sea ice is strongly affected by it's fracture into small pieces by ocean surface waves, which can lead to a local albedo effect and contribute to global-scale changes in the sea ice cover. I'll also discuss how lateral density gradients that form at the boundaries of floes can lead to overturning at floe edges, mixed layer instability and energetic sub-mesoscale ocean eddies that spread from the ice edge towards both open water and ice covered regions, mixing heat laterally and driving melting of large floes near their edges. I'll show that the timing of ice melt in a typical climate model grid cell is sensitive on the order of weeks to months to changes in the FSD for floes with length scales of O(10) km, several orders of magnitude larger than previously considered important.
Thursday 28 April 2016 - 15:00 to 16:00
NOC Southampton - Henry Charnock Lecture Theatre (Waterfront Campus).
Chris Horvat (Harvard University, Cambridge)