Ocean circulation and shelf processes in the Arctic Mediterranean traced by radiogenic neodymium isotopes, rare earth elements and stable oxygen isotopes

• Main Author: Laukert, Georgi
• Format: Thesis
• Language: English
• Published: 2017
• Subjects: Arctic; Arctic Ocean; Svalbard; Greenland; Fram Strait; Nordic Seas; Sea ice
• Online Access: https://oceanrep.geomar.de/id/eprint/36997/; https://oceanrep.geomar.de/id/eprint/36997/1/Dissertation_Georgi_Laukert_2017.pdf; https://nbn-resolving.org/urn:nbn:de:gbv:8-diss-204798

The warming of the Arctic region in the recent past has proceeded at rates double that of the global average and has been accompanied by rapid sea ice retreat and increased heat and freshwater fluxes to the Arctic Mediterranean (i.e. the Arctic Ocean and the Nordic Seas, AM). Further warming will have strong impacts on ocean circulation, freshwater pathways, and marine ecosystems in the AM. Disentangling the sources, distribution and mixing of water masses involved in the transport and transfer of heat and freshwater is therefore critical for the understanding of present and future hydrological changes in the high-latitude and polar regions and their consequences. This study refines the knowledge of water mass circulation and mixing in the AM and provides new insights into the processes occurring on the Arctic shelves and in high-latitude estuaries. A multi-proxy approach is used combining dissolved radiogenic Nd isotopes (εNd), rare earth elements (REEs) and stable oxygen isotopes (δ18O) together with standard hydrographic tracers. The sources, distribution and mixing of water masses that circulate in the AM and pass the Fram Strait are assessed through evaluation of dissolved εNd and REE, and δ18O data obtained from samples recovered in 2012 along a full water depth section extending between Svalbard and Greenland at ~79 °N, and through a compilation and reassessment of literature Nd isotope and concentration data previously reported for other sites within the AM. The Nd isotope and REE distribution in the central Fram Strait and the open AM primarily reflects the lateral advection of water masses and their mixing, whereas seawater-particle interactions exert important control only above the shelf regions. For example, on the NE Greenland Shelf, remineralization of biogenic and/or release from detrital particles is recorded in bottom waters. Advection of warm Atlantic Water (AW) in the upper water column of the eastern and central Fram Strait is clearly reflected by an εNd signature of -11.7 and a Nd ...