Arctic Ocean warming: submarine and acoustic measurements

Abstract

In 1993 the USS Pargo made the first Submarine Science Expedition (SCICEX) to the Arctic Ocean. In April 1994 the first Transarctic Acoustic Propagation (TAP) experiment designed to measure Arctic Ocean temperature was conducted. SCICEX cruises to the Arctic followed annually from 1995 to 2000. Expendable CTDs and on some cruises standard CTDs were deployed along or close to the TAP acoustic section. In October of 1998 as part of the Arctic Climate Observations using Underwater Sound (ACOUS) program a source was deployed in the Franz Victoria Strait and a receive array was deployed in the Lincoln Sea. In April 1999 a second acoustic section was made across the Arctic when recordings of the ACOUS source were made at the APLIS Ice Camp in the Chukchi Sea as part of the support to SCICEX 1999. Comparisons between the acoustic sections and the SCICEX sections have shown that measurement of the average temperature in the Atlantic Layer is easily and very reliably accomplished using acoustic thermometry. Furthermore, all of these measurements have documented the steady rise in the temperature of the Atlantic Layer starting in the early 1990s. The SCICEX 2000 cruise is the last scheduled SCICEX cruise to the Arctic. Future scientific measurements in the Arctic by submarine will be accomplished intermittently on a not-to-interfere basis in conjunction with naval operations. Analysis of the first acoustic thermometry time series record from Oct. 1998 through Dec. 1999 is underway after the successful recovery of the ACOUS Lincoln Sea receive array in March 2001. SCICEX results and the acoustic thermometry time series results are presented. Acoustic thermometry can provide a long-term reliable capability for monitoring Arctic Ocean temperature and other variables including the thermocline depth. This can be accomplished by including acoustic receivers and sources on moorings that are currently under consideration for deployment in the Arctic under the proposed Study of Environmental Arctic Change (SEARCH) program.