Here, we report about recent and upcoming expeditions.

MSM 81 'Falkland sediment drifts' - taking RV Maria S Merian to the Falkland Plateau

Onset and modifications in intensity and pathways of water mass exchange between the Southeast Pacific and the South Atlantic: A focus on the Falkland Plateau

The opening of Drake Passage and the Scotia Sea, the gateway between South America and Antarctica, enabled the exchange of water masses between the southern Pacific and the South Atlantic. In this way heat and energy could be transferred between the two oceans. Together with the opening of the Tasman Gateway this allowed the establishment of the Antarctic Circumpolar Current (ACC) thermally isolating Antarctica, which has been considered as one of the major causes for the onset of widespread glaciation. Both tectonic movements within Drake Passage and the Scotia Sea as well as modifications in climate have led to changes in intensity and pathway of the ACC and the water masses flowing within it. The onset of the ACC and those changes have been documented in sedimentary structures deposited on the Falkland Plateau.  

The deep and bottom water masses flowing within the ACC (Antarctic Bottom Water (AABW), WSDW, SPDW, LCDW, UCDW) are steered by the complex topography of the Drake Passage and the Scotia Sea. Rounding topographic highs the water masses reduce their speed and hence deposit sediment. In gaps and passages their speed is increased leading to erosion and non-deposition. In this way the aforementioned water masses shape sediment drifts, which in their structure (geometry, internal unconformities, reflection characteristics) document the modifications in the flow paths and intensities of the water masses. The tectonic development of both the Drake Passage and the Scotia Sea during the Cenozoic have led to strong modifications in the flow paths, which, when studying sediment drifts, can be deciphered. Additionally, the ACC fronts are assumed to have been subject to relocations during glacial-interglacial cycles. This again has led to relocations in depocentres, which can be identified via seismic profiles. So far, research here has concentrated on the area south of the Falkland Islands towards South America but the flow of water masses across the plateau has not been studied. Results of DSDP Legs 36 and 71 suggest intensified bottom currents as early as the Eocene, which led to the discussion of an early Tertiary water mass exchange between the Pacific and the Atlantic oceans . Numerical simulations also suggest a weak ACC for the late Cretaceous but no overturning circulation.

RV Marian S Merian cruise MSM 81

Cruise Leg MSM 81 with RV Maria S. Merian, planned to leave San Antonio, Chile on 4.2.19, and return to Montevideo, Uruguay on 14.3.19, will concentrate on seismic reflection and bathymetric studies of the Falkland Plateau. The overaching goals of the proposed cruise are twofold: we intend to study variations in flow paths and intensities of deep and bottom water masses in response to a) tectonic movements, and b) climate variability.

In particular, we intend to answer the following questions:

  • When and how did the onset of the ACC and the deep and bottom water masses flowing within the ACC affect sedimentation at the Falkland Plateau area?
  • When can we recognise the first overspill of UCDW and LCDW over the Falkland Plateau indicating transport of cold water masses into the South Atlantic?
  • What are the variations of the pathways and intensity of overspill and the location of the ACC fronts in relation to a) tectonic movements, and b) modifications in climate (e.g. Mid-Miocene Climatic Optimum and Transition, Pliocene warming, onset of widespread glaciation on the Northern Hemisphere)?

Acknowledgements

This project has been funded by the Deutsche Forschungsgemeinschaft under the scope of the German Research Vessels.

Collaboration partners

MARUM, University Bremen, Bremen, Germany
Dr. Thomas Westerhold

National Oceanographic Centre, Southampton, UK
Prof. Dr. Steve Bohaty

British Antarctic Survey, Cambridge, UK
Dr. Robert D. Larter

MSM 44 'BAFFEAST' - with FS Maria S. Merian into the northeastern Baffin Bay

In the Baffin Bay, palaeoclimate, palaeoceanography and the past development of the Greenland Ice Sheet are tightly coupled. For the northeast Baffin Bay, in which 27% of the western Greenland Ice Sheet drain, this connection has not yet been established due to the lack of data and samples. In order to model responses of the GIS to changing climatic conditions, and hence, changing oceanographic conditions, it is important to better understand the nature of these ocean-ice sheet couplings and related ice sheet dynamics in this area.

For this reason, the bathymetry working group at the AWI systematically maps the shelf and slope of the northeast Baffin Bay for seabed features associated to past Greenland Ice Sheet advances and retreats and bottom current activity. These studies are supplemented by proxy-studies done at the MARUM to date these features and events. These combined bathymetric/palaeoceanographic studies aim to provide information on the ocean circulation patterns in the northeast Baffin Bay, and thus, the palaeoceanographic influences on the northwest Greenland Ice Sheet.

During July 2015, an expedition to the Baffin Bay on RV Maria S. Merian will take place.

impressions from the mess room... ;-)

 

 

 


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