Calving cycle of Ninnis Glacier over the last 60 years

Abstract

Iceberg calving is one of the contributing ways for the mass loss from ice shelves in Antarctica; the calving cycles of most ice shelves are quite long. The mechanism of iceberg calving has not been well investigated because of the limited temporal coverage of satellite observations. The Ninnis Glacier (NG) has experienced three calving events in the past 60 years (1980–1982, 1998, and 2018), which provides an opportunity to capture the long-term pattern of calving for the first time. In our study, ARGON, Landsat, and ERS-2 images were combined with field measurements to characterize the evolution of the Ninnis Glacier, especially for the last calving event, which can be studied using high-quality observations. The time span was over 23 years for the 1st calving cycle and the average time span was ∼18.5 years for each of the last two cycles. Supported by satellite-derived strain rates and ocean currents obtained from a numerical ocean model, we conclude that the calving of the Ninnis Glacier Tongue (NGT) was driven by the continuous impact of ocean current on the advected glacier tongue. According to a comparison among the three calving events, the calving area of the last calving event was ∼750 km2, only half of the 1st calving event, with breaking locations closer to the grounding line. We attribute these changes to the reduction of fast ice in this region, which can be related to the local oceanographic conditions.

Keywords

• Antarctica
• Ice Shelf
• Ninnis Glacier
• Calving Cycle