Mass-Balance Aspects of Weddell Sea Pack Ice

Abstract The Weddell Sea pack ice undergoes several unique advance–retreat characteristics related to the clockwise transport in the Weddell Gyre, the physical setting for the pack ice, and the free boundary with the oceans to the north. From satellite-derived ice charts, the annual cycle of the pack ice advance and retreat is depicted. The Weddell pack advance is characterized by a strong east-moving component as well as the north advance seen in other regions such as East Antarctica. Physical characteristics of the pack ice at the summer minimum ice edge are presented. Indications are that deformation is a significant component of the ice accumulation, deformed ice accounting for c. 15 to 20% of the area covered in the year-round pack. Ablation characteristics are inferred from observations made during field work and from satellite imagery. These observations indicate that surface-melt ablation typically seen on Arctic pack is not seen on the Weddell pack inside the summer edge. Using the physical-property data and transport inferred from ship and iceberg drifts, a new annual ice accumulation η < 3 m is inferred over the continental shelf in the South compared to η < 2 m previously estimated (Gill, 1973). The implication is that salt flux into the ocean over the shelf may be significantly larger, thereby increasing the production of Western Shelf Water, a component of Antarctic Bottom Water.

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