Eos, Vol. 76, No. 27, July 4, 1995 Eos, TRANSACTIONS, AMERICAN GEOPHYSICAL UNION EOS VOLUME 76 NUMBER 27 JULY 4,1995 PAGES 265-272 Experiment Tests Use of Acoustics to Monitor Temperature and Ice in Arctic Ocean PAGES 265,268-269 Peter N. Mikhalevsky, Arthur B. Baggeroer, Alexander Gavrilov, and Mark Slavinsky A recent experiment conducted to test whether Arctic Ocean temperature change and sea ice thickness and roughness can be monitored using long-range, low-frequency acoustics was a resounding success. The Transarctic Acoustic Propagation (TAP) ex- periment, conducted in April 1994, showed that acoustic thermometry can be used to col- lect year-round data in this critical, sensitive part of the global climate system. The oceanographic structure of the Arctic and the depth distribution of the acoustic modes make the Arctic especially suitable for acoustic thermometry. In fact, acoustic thermometry has many advantages for col- lecting climate data in the Arctic over satellite, icebreaker, or submarine. Long- term observations of the changes in acoustic phase, travel time, and amplitude of many transarctic paths could provide synoptic measurements of Arctic Ocean temperature and sea ice properties, particularly average ice thickness [Mikhalevsky etai, 1991]. Arc- tic Ocean temperature change is impossible to obtain with satellites, and synoptic long- term monitoring is difficult and expensive with ice breakers and submarines. Arctic Climate in the Global System The Arctic climate plays a major role in the Earth's global climate system and is a sen- Peter N. Mikhalevsky, Science Applications In- ternational Corporation, 1710 Goodridge Dr., McLean, V A 22102; Arthur B. Baggeroer; Massachusetts Institute of Technology, 77 Mas- sachusetts Ave., Cambridge, MA 02139; Alexan- der Gavrilov; Ocean Acoustics and Information Co. (Acoustinform) LTD., 38 Vavilov St., 117942 Moscow, Russia; Mark Slav- insky, Institute of Applied Physics, 46 Uljanov St., 603600 Nizhny Novgorod, Russia sitive indicator of global climate change. The annual changes in surface albedo that accompany the melting and formation of sea ice and snow affect the energy received by the Earth-atmosphere system, the global meridional temperature gradient, and zonal atmospheric circulation. The Arctic Ocean provides fresh water to the North Atlantic in the form of lower-salin- ity surface water above the strong Arctic Ocean halocline and sea ice and helps strat- ify the gyres that drive the global thermohaline circulation. A 1 % yr" 1 increase in atmospheric CO2 [Manabe et al., 1991] causes a greater increase in the atmospheric temperature over the Arctic than at temper- ate latitudes, a thinning and retreat of the Arctic sea ice and snow cover, and a warm- ing of Arctic Ocean waters, according to the Geophysical Fluid Dynamics Laboratory gen- eral circulation model. Fig. 1. Geographical locations of the source and receiver camps of the Transarctic Acoustic Propagation experiment. Original color image appears at the back of this volume. This page may be freely copied.