Radionuclides in the Weddell Sea, supplement to: Rutgers van der Loeff, Michiel M (1994): 228Ra and 228Th in the Weddell Sea. In: Johannessen, O M; Muench, R D & Overland, J E (eds.), The polar oceans and their role in shaping the global environment. Geophysical Monograph Series, American Geophysical Union, 540 pages, ISBN 0-87590-042-9, 85, 177-186

• Main Author: Rutgers van der Loeff, Michiel M
• Format: Article in Journal/Newspaper
• Language: English
• Published: PANGAEA - Data Publisher for Earth & Environmental Science 1994
• Subjects: Multiple investigations; Sampling gear, diverse; Water sample; ANT-IX/3; ANT-X/6; ANT-VIII/3; Polarstern; Marine Geochemistry @ AWI AWI_MarGeoChem; Paleoenvironmental Reconstructions from Marine Sediments @ AWI AWI_Paleo; Antarctic; The Antarctic; Weddell Sea; Weddell; Johannessen; Antarc*; Ice Shelf
• Online Access: https://dx.doi.org/10.1594/pangaea.730454; https://doi.pangaea.de/10.1594/PANGAEA.730454

228Ra and its granddaughter 228Th were measured on a N-S transect from 45's to the Antarctic continent across the Antarctic Circumpolar Current (ACC) and the Weddell Sea. The distributions of 230Th, 228Th and 228Ra show that southward transport across the ACC of Circumpolar Deep Water (CDW), the source of Warm Deep Water (WDW) in the Weddell Sea, occurs on a time scale between 8 and 30 years, in qualitative agreement with estimates of the upwelling rate of WDW. The distribution of 228Ra in deep waters is controlled by advection and isopycnal mixing rather than diapycnal mixing. In the Weddell Sea, deep-water 228Ra activities reach 15-20 dpm/m**3. Enrichment in deep water is controlled by the production in the deep-sea floor, favoured by low biogenic sediment accumulation rates and consequently high 232Th contents in the surface sediment (3 to 5 dpm/g). The highest 228Ra value (73 dpm/m**3) was observed near the sea floor in a channel where an eastern outflow of Weddell Sea Bottom Water (WSBW) is suspected. It is not yet known whether this value is produced in-situ by accumulation in the stratified bottom water, or contains a Signal of enrichment in shelf- and Ice Shelf Water. High 228Ra activities on the south-eastem shelf (22 dpm/m**3) and low activities offshore yield an estimated residente time of 1.5 years on this shelf and imply slow exchange with offshore waters.