Acoustic thermometry along an Arctic Ocean path

Acoustic thermometry has been shown to be a very effective technique for monitoring average heat content and average temperature in the Arctic Ocean and in particular in the Arctic Intermediate Water (AIW) layer. As part of the U.S./Russian Arctic Climate Observations using Underwater Sound (ACOUS) program a 14-month time series of acoustic transmissions were analyzed along a 1250 km propagation path that extended from the Franz Victoria Strait to the Lincoln Sea from Oct. 1998 through Dec. 1999. The receive array mooring in the Lincoln Sea was recovered in April 2001. Modal travel times were estimated after pulse compression processing and mode filtering of the vertical line array. The interarrival time between mode 1 and modes 2 and 3 show net cooling during the first several months followed by a dramatic warming of the AIW along the propagation path. This warming is consistent with direct CTD measurements made along a central Arctic transect performed by the USS Hawkbill during the Scientific Ice Exercise (SCICEX) 2000. [Work supported by ONR, NSF, the Civilian Research and Development Foundation, and the Ministry of Industry, Science and Technology of the Russian Federation.]