Sea-ice surface properties and their impact on the under-ice light field from remote sensing data and in-situ measurements

• Main Author: Arndt, Stefanie
• Other Authors: Lemke, Peter, Nicolaus, Marcel, Haas, Christian
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universität Bremen 2017
• Subjects: sea ice; snow; Antarctic; Arctic; surface properties; melt processes; energy budget; mass budget; light; field work; passive microwave observation; active microwave observations; 530; 530 Physics; ddc:530; Antarc*; Antarktis*; Arktis*; Sea ice
• Online Access: https://media.suub.uni-bremen.de/handle/elib/1182; https://nbn-resolving.org/urn:nbn:de:gbv:46-00105734-13

The surface properties of sea ice dominate many key processes and drive important feedback mechanisms in the polar oceans of both hemispheres. Examining Arctic and Antarctic sea ice, the distinctly different dominant sea-ice and snow properties in spring and summer are apparent. While Arctic sea ice features a seasonal snow cover with widespread surface ponding in summer, a year-round snow cover and strong surface flooding at the snow/ice interface is observed on Antarctic sea ice. However, substantial knowledge gaps exist about the spatial distribution and temporal evolution of these properties, and their impacts on exchange processes across the atmosphere/ocean interface. This thesis aims to overcome these limitations by quantifying the influence of surface properties on the energy and mass budgets in the ice-covered oceans. Remote sensing data and in-situ observations are combined to derive the seasonal cycle of dominant sea-ice surface characteristics, and their relation to the transfer of solar radiation from the atmosphere through snow and sea ice into the upper ocean. This thesis shows that characteristics of the solar radiation under Arctic sea ice can be described directly as a function of sea-ice surface properties as, e.g., sea-ice type and melt pond coverage. Using this parameterization, an Arctic-wide calculation of solar radiation through sea ice identifies the surface melt onset as the main driver of the annual sea-ice mass and energy budgets. In contrast, an analysis of the spring-summer transition of Antarctic sea ice using passive microwave satellite observations indicates widespread diurnal freeze-thaw cycles in the top snow layers. While the associated temporary thawing is identified as the predominant melt process, subsequent continuous melt in deeper snow layers is rarely found on Antarctic sea ice. Instead of directly influencing the snow depth on Antarctic sea ice, these melt processes rather modify the internal stratigraphy and vertical density structure of the snowpack. An additional ...