A NOTE ON INFRAGRAVITY WAVES IN THE ARCTIC-OCEAN

Long-period (20-50 s) surface-gravity waves were recorded in the easte rn Arctic (83 degrees N, 10 degrees E) using tiltmeters deployed on th e ice and an acoustical current meter deployed a few meters below the ice during the spring of 1989. The waves caused ice tilt of a few micr oradians and horizontal velocity of the water just beneath the ice of order 10(-4) m s(-1). The unprecedented sensitivity of the velocity me asurements is the result of a path-averaging technique based on recipr ocal transmission along 200-m horizontal paths. The measurements indic ate that infragravity waves and low-frequency swell penetrate the Arct ic Ocean through the Fram Strait and that they are freely propagating and not tied to groups of short waves. It is suggested that these wave s could provide a method to measure ice thickness distribution in the Arctic Ocean.