Radioactive Tracers in the Greenland Sea

Abstract

Under the Icelandic/Danish part of the international Greenland Sea Project, ⁹⁹Tc, ¹³⁴Cs, ¹³⁷Cs and ⁹⁰Sr have been measured in large volume water samples taken between Jan Mayen and East Greenland and across the Denmark Strait. A sampling in September 1988 has given the following results:

• Inputs of technetium-99 from European discharges during the 1970’s and 1980’s have resulted in Greenland Sea concentrations of 25 – 100 mBq m^-3 by 1988. As the Irminger Water south of Iceland only contains approximately 10 mBq m^-3, ⁹⁹Tc is very promising as a tracer for the overflow of Greenland Sea water over the Denmark Strait sill. The results indicate a rapid exchange rate for the Greenland Sea water masses.

• Radiocaesium from the Chernobyl accident in 1986 appeared in 1988 in relatively high subsurface concentrations in the intermediate water at 80 – 300 meter. This is in accordance with a fast subsurface transport through the Greenland Sea of surface water originating in the Norwegian Coastal Current/West Spitzbergen Current.

• There are indications of high Chernobyl contributions in a water mass at 700–1400 meter. The measurements indicate that this water mass could contain a surface water contribution from a region receiving a relatively high amount of Chernobyl debris two years prior to the sampling. Alternatively, a scavenging of particulate radiocaesium from the Chernobyl accident immediately after the deposition in 1986 could also explain these measurements.