Die Rolle des Ostgrönlandstroms in der Klimavariabilität der letzten 200 Jahre im Nordatlantik
Zusammenfassung der Projektergebnisse
The projects ‘GreenClime I & II’, focused on millennial to decadal resolved reconstructions of the East Greenland Current (EGC) evolution since mid Holocene times towards the present, i.e. c. last 6.5 ka BP, and its role in the subpolar North Atlantic climate variability. In order to elucidate changes in the EGC’s properties, a set of multi-proxy analyses was applied to reconstruct surface mass characteristics along the East Greenland (site 1 and 2) and North Iceland (site 4) shelf, as well as on the Reykjanes Ridge (site 3). Subsurface water mass reconstructions from these sites allowed to study, parallel, the interaction between the fresh/cold surface waters carried by the EGC and the underlying warm/saline Atlantic waters. The new available proxy records contribute to an improved (high-resolution) documentation of palaeoceanographic changes on the (central) East Greenland shelf and the influence of freshwater forcing via the EGC on the North Atlantic’s oceanic fronts, i.e. Polar and Subarctic Front. In the time from c. 6.5 to 4.5 ka BP, reveal surface and subsurface water reconstruction enhanced surface water productivity along the East Greenland shelf, ascribed to the influence of the Polar Front. Such conditions likely relate to the occurrence of freshwaters and an enhanced influence of warm and relatively saline subsurface waters on surface water conditions on the central East Greenland shelf and in northern Denmark Strait. Likely prevailed a predominant freshwater influence by the EGC during the periods. These conditions parallel an intensification of the Subarctic Front south of Iceland that result from reduced solar activity that favoured Ice Sheet and glacier advances into tidewater. The strong northward heat advection towards the SE Greenland shelf area likely melted the drift ice and icebergs carried by the EGC and enhanced freshwater contribution to the subpolar North Atlantic region. Subsequent to this relative warm phase on the East Greenland shelf occurred a pronounced increase in the drift/sea ice load of the EGC, likely driven by enhanced export from the Arctic Ocean via western Fram Strait and caused a substantial cooling of surface waters and stratification of the water column. This EGC strengthening culminated in the time between c. 2.4 to 1.4 ka BP and parallels the strongest phase of the northward heat advection into the northern North Atlantic by the North Atlantic Current and its offshoots, the Roman Warm Period. Such conditions are evident from distinct subsurface warming along the East Greenland shelf and a prominent Subarctic Front intensification south of Iceland. However, subsequent from c. 1.5 ka BP onwards occurs a markedly reduced northward heat advection, while the EGC seems to have remained relatively strong. Recent surface and subsurface water reconstructions from the North Iceland shelf, which comprise the last c. 150 years, elucidate that the EGC holds a continuous strong influence on oceanic conditions within the area and particularly since the 1960s AD. Prior this time, from the 1920s to 1960s AD, prevailed relatively warm subsurface water conditions on the North Iceland shelf and a minor Polar Front influence. The intensification of the Polar Front since the mid-20th century, likely relates to the occurrence of the Great Salinity Anomalies, i.e. enhanced freshwater and/or sea ice export from the Arctic Ocean. These modern events of frontal intensification may similar as the reconstructed mid and late Holocene phases of Subarctic Front intensification result from a feedback of enhanced northward heat advection by the North Atlantic Current that fuels Arctic Ocean freshwater and sea ice export.
Projektbezogene Publikationen (Auswahl)
- (2015). Holocene millennial-scale variability of the East Greenland Current and warm subsurface Atlantic waters in northern Denmark Strait. 45th International Arctic Workshop, May 2015
Perner, K., Jennings, A.E., Andrews, J.T., Moros, M., Wacker, L., Jansen, E.
- (2015). Mid to late Holocene palaeoceanographic evolution of the East Greenland Current based on foraminiferal assemblage data. Past Gateways Meeting, May 2015
Perner, K., Moros, M., Lloyd, J.M., Jansen, E., Stein, R.
- (2015). Mid to late Holocene strengthening of the East Greenland Current linked to warm Atlantic Water. Quaternary Science Reviews 129: 296-307
Perner, K., Moros, M., Lloyd, J.M., Jansen, E., Stein, R.
(Siehe online unter https://doi.org/10.1016/j.quascirev.2015.10.007) - (2015). Mid to late Holocene strengthening of the East Greenland Current paralleled by increased Atlantic Intermediate Water outflow from the Arctic Ocean. European Geoscience Union, April 2015
Perner, K., Moros, M., Lloyd, J.M., Jansen, E., Stein, R.
- (2016) Reconstruction of sea-ice cover and primary production on the East Greenland Shelf (73°N) during the last 5200 years. European Geoscience Union, April 2016
Kolling, H., Stein, R., Fahl, K., Perner, K., Moros, M.
- (2016). A 200 years record of multidecadal oceanographic changes from offshore North Iceland. European Geoscience Union, April 2016
Perner, K., Moros, M., Jansen, E.
- (2016). Interaction between warm Atlanticsourced waters and the East Greenland Current in northern Denmark Strait (68°N). Journal of Quaternary Science 31, 472-483
Perner, K., Jennings, A.E., Moros, M., Andrews, J.T.
(Siehe online unter https://doi.org/10.1002/jqs.2872) - (2016). Late Quaternary changes in sediment composition on the NE Greenland margin (~73°N) with a focus on the fjords and shelf. Boreas 45, 381-397
Andrews, J.T., Stein, R., Moros, M., Perner, K.
(Siehe online unter https://doi.org/10.1111/bor.12169)
