Observation of warm water transport and mixing in the Arctic basin with the ALTEX AUV

An autonomous underwater vehicle (AUV) designed for operation at high latitudes and under ice, completed its first Arctic field tests from the USCGC Healy in October 2001. The ALTEX (Atlantic Layer Tracking EXperiment) AUV´s initial application was focused on tracking the warm Atlantic Layer inflow - the primary source of seawater to the Arctic Ocean. The primary payloads were twin pumped CTD systems. Oxygen and nitrate sensors provide the ability to use NO (dissolved oxygen corrected by nitrate to account for biological respiration) as a nearly conservative tracer. An ice profiling sonar allowed the AUV to estimate the ice thickness in real-time and was designed to generate high quality post-processed ice draft data comparable to that collected through the SCICEX program. Sections of water properties were obtained in the marginal ice zone and ice thickness measurements made in the ice pack. Marginal ice observations showed mixing of the warm Atlantic layer to the surface, causing melting of ice even as winter approached.