CPP-16. Surface elevation change of the outlet glaciers flowing into the former Larsen A and B Ice Shelves using 60 year old trimetrogon aerial imagery

Ice shelves are an integral component to maintaining the mass balance of the Antarctic Ice Sheet. Significant changes to ice shelves affect the flow dynamics of their incoming glaciers and subsequently sea level rise. At the Antarctic Peninsula, the Larsen A Ice Shelf collapsed in 1995 and the Larsen B Ice Shelf followed suit in 2002. One outcome from the breakup events is that their outlet glaciers also underwent dramatic increases in their ice discharge rates with the removal of ice shelf buttressing forces. Past research shows that surface temperatures began increasing in the region as early as the 1930s and the enhanced surface melt from higher temperatures was a contributing factor to ice shelf disintegration; however, due to large temporal gaps in observational data collection in this part of Antarctica, little is known about the dynamics of the two ice shelves and their feeding outlet glaciers in the decades leading up to the collapses. One goal of this study is to increase the temporal resolution of observations by using historical data to assess ice shelf and glacier hypsometry. We present the earliest high resolution elevation results derived from 1960s trimetrogon aerial (TMA) imagery for the Larsen A and B Ice Shelves and their major outlet glaciers: Crane, Hektoria-Green-Evans, and Dinsmoor-Bombardier-Edgeworth Glaciers. TMA data are photographs taken with one vertical (0° nadir) and two oblique (~30° off-nadir) cameras simultaneously. The surface elevations generated in this study are done so using both types of imagery with structure-from-motion photogrammetry software. The ground control used in the bulk bundle application is exposed bedrock features extracted from high resolution (0.5 m) satellite imagery derived elevations. Results provide an improved understanding of the changes the ice shelves and their outlet glaciers were undergoing ~30-40 years prior to the breakup events. This work is in support of a larger study examining the pre- and post-observations of the Larsen A and B marine terminating glaciers’ dynamics surrounding potential ice cliff failure events.