Monitoring seasonal basal melting of ice shelves using fiber-optic distributed temperature sensing

Abstract:

Ice shelf basal melt rates represent an important, yet challenging measurement for understanding ice-ocean interactions and climate change. In November 2011, two moorings containing fiber-optic cables for distributed temperature sensing (DTS) were installed through the McMurdo Ice Shelf at Windless Bight, Antarctica, penetrating ~200m of ice and extending ~600m into the ice shelf cavity. Annual basal melt rates in the region are estimated to be close to the 1m resolution of the DTS system. However, the smooth thermal profile of ice shelves and high spatial resolution of DTS allows for transient monitoring of the thermal gradient close to the ice-ocean interface. By utilizing the thermal gradient near the interface we are able to resolve the interface location more precisely and at a higher spatial resolution than the field deployed DTS system. The thermal gradient near the ice-ocean interface is extrapolated to the in situ freezing temperature in order to continuously track the interface and to estimate seasonal melt rates. Maximum melting corresponds with the arrival of seasonal warm surface water in the ice shelf cavity and is estimated to be 8.5mm∙d^-1, approximately ten times greater than the observed winter melt rate. The development of a continuous, surface-based, measurement technique for ice shelf basal melting represents a significant advance in our ability to monitor ice shelf stability and ice-ocean interactions.