Journal
BIOGEOSCIENCES
Volume 12, Issue 5, Pages 1415-1430Publisher
COPERNICUS GESELLSCHAFT MBH
DOI: 10.5194/bg-12-1415-2015
Keywords
-
Categories
Funding
- CNES
- French Research program of INSU-CNRS LEFE-CYBER (Les enveloppes fluides et l'environnement - Cycles biogeochimiques, environnement et ressources)
- ANR (Agence Nationale de la Recherche, SIMI-6 program) [ANR-10-BLAN-0614]
- CNES (Centre National d'Etudes Spatiales)
- IPEV (Institut Polaire Paul-Emile Victor)
Ask authors/readers for more resources
The Southern Ocean is known to be the largest high-nutrient, low-chlorophyll (HNLC) region of the global ocean due to iron limitation. However, a large phytoplankton bloom develops annually downstream of the Kerguelen Islands, a bloom which is sustained partly by iron released from the sediments deposited onto the shelves. In the framework of the KEOPS-2 project, we used radium isotopes (Ra-224, T-1/2 = 3.66 d; Ra-223, T-1/2 = 11.4 d; Ra-228, T-1/2 = 5.75 yr) to provide information on the origin of iron fertilization and on the timescales of the transfer of sedimentderived inputs (including iron and other micronutrients) towards offshore waters. Significant Ra-224 and Ra-223 activities were found in the near vicinity of the Kerguelen Islands, in agreement with the short half-lives of these isotopes. Significant Ra-224 and Ra-223 activities were also detected up to 200 km downstream of the islands and more unexpectedly in offshore waters south of the polar front. These observations thus clearly indicate (i) that the sediment-derived inputs are rapidly transferred towards offshore waters (on timescales on the order of several days up to several weeks) and (ii) that the polar front is not a physical barrier for the chemical elements released from the sediments of the Kerguelen Plateau. The Ra data set suggests that iron and other micronutrients released by the shelves of the Kerguelen Islands may contribute to fueling the phytoplankton bloom downstream of the islands, despite the presence of the polar front. However, the heterogeneous distribution of the Ra-224 and Ra-223 activities in surface waters suggests that this supply across the front is not a continuous process but rather a process that is highly variable in space and time.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available