Reduction and Loss of an Ice Shelf in Elizabeth City State University Bay, Antarctica: 1972–2003

Gradual reduction of a small ice shelf in the Pine Island Bay area is measured using eleven Landsat images spanning 1972 to 2003. Measurements of Ice shelf area indicate that it expanded slightly during the first two decades of observations from approximately 6.19 km ² measured on December 7, 1972 to a maximum of about 6.82 km² observed in 1986. This maximum was followed by a nearly continuous decrease in area and ultimate disappearance of the ice shelf by January 17, 2003. No ice shelf has reappeared since 2003 as observed in subsequent Landsat images. Ten of the eleven Landsat images were co-registered and warped to one of a pair of 2003 geographic reference images before area measurement. Individual study team members made independent measurements of the ice shelf area apparent in each image. The average of these measurements had a standard deviation of 0.14 km² . The specific cause of this ice shelf disappearance is unknown, but is probably related to increased basal melting by warmer ocean waters reaching Pine Island Bay. Intrusions of warm “Circumpolar Deep Water” are related to ice shelf and outlet glacier thinning and retreat as reported throughout the Amundsen Sea region. This is the first report of complete ice shelf loss so far south or in the Amundsen Bay region. This small, previously unnamed ice shelf formerly occupied what is now known as the Elizabeth City State University Bay.