DETERMINATION OF ICE-SHELF BOTTOM MELTING BY TIME-DOMAIN REFLECTOMETRY

For our work in the Filchner-Ronne Ice Shelf Programme (FRISP), we have developed a new technique for measuring the bottom-melting rate with high reliability. The method is based on time-domain reflectometry (TDR) measurements of transmission lines inserted into melt holes. The TDR-data are digitally recorded on magnetic tape. System resolution has been estimated at 0.2 m. Hence, re-measuring after 1 year gives an accuracy of 10% for melting rates of 2 m a-1. Two transmission lines for TDR measurements were installed during the German FRIS Expedition 1989-90. This paper describes the design of the system. Examples of recorded wave forms are given.