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Vrije Universiteit Amsterdam

The Vrije Universiteit Amsterdam (VUA) team aims to quantify the Late Pleistocene dynamics of meridional frontal movements and the Indian - Atlantic watermass exchange including key watermass characteristics of surface and thermocline Agulhas Leakage waters, in order to assess the potential impact of this leakage on the transient evolution of the Atlantic MOC and southern African climates. Central to these aims are the quatification of rates and magnitudes of the dynamics of the transient system between different ocean-climate modes. Using marine sediment cores the VUA team will, in close collaboration with UAB and CU, produce planktonic micropalaeontological / geochemical proxy time series, and contribute to the development of new proxies, to quantitatively assess the above mentioned aims. The VUA team makes the reconstructions and proxy data available to collaborating partners in the consortium that serve as input for: i) statistical assessment of leakage-mode variability and ii)  to shape the boundary conditions for numerical models simulations for time slices of extreme modes of the leakage system (i.e. for the full glacial and full interglacial mode). 

The analytical programme entails census counts of fossil planktic foraminifera indicative for different water-masses and characterisic for the relative meridional position of ocean fronts be performed. A previously established planktic foraminifeal depth habitat model is tested, validated and applied to extract T - S characteristic information of the surface and sub-surface water mass using paired d18O and Mg/Ca ratios on various species indicative for different depths and different water masses. Furthermore, in house fascilities for grainsize analyses and available expertise in end member modelling of grainsize distributions using the End Member Modelling Algorithm ‘EMMA', as well as the on-line dD analysis of fluid inclusion water in speleothems are available to network partners.

The sediment sample material available within the consortium is studied and shared to ensure different proxies are measured on the same sample material. Planktic foraminiferal assemblage analyses as well as d18O and Mg/Ca ratios analyses are carried out in cross-collaboration with UAB, CU and NIOZ partners to ensure work is complementary (and not duplicatory). Sedimentological work on grainsize analysis and endmember modelling in collaboration partner CU and UAB, and the use of the continuous - flow crushing device for on-line d2H analysis of fluid inclusion water in speleothems with partner GSI. Statistical analyses of proxy time series in collaboration with partner CRA. Proxy time series data generated are made available to network partners.



The VUA team concentrates on surface-ocean and thermocline T-S patterns as indicators of varying warm/salt water transports in the Agulhas Current and leakage into the South Atlantic (cross-linking with partners UAB, NIOZ and CU); surface ocean property gradients as indicators for the migration of regional ocean fronts, with implications for the geometry of the Indian-Atlantic ocean gateway (cross-linking with partner UAB, IFM-GEOMAR); land-ocean climatic coupling through the comparison of surface ocean conditions within the Agulhas Current System and South African terrestrial climates (cross-linking with partner GSI, UCT); linking between salt water leakage and buoyancy transports from the Indian Ocean to the Atlantic and mode shifts of the Atlantic MOC (cross-linking with partner CU, IFM-Geomar).

 

Partner Profile

The Faculty of Earth and Life Sciences of the Department of Earth Sciences of the VUA maintains a dedicated focus on marine ocean-climate research and ocean-climate training of B.Sc, M.Sc. and Ph.D. students. VUA hosts a Masters Programme on ‘Paleoclimate and Geo-ecosystems' with an average of four Ph.D. theses produced each year. VUA was and is involved in large international programs such as JGOFS, IMAGES, and IODP as well as a number of European projects such as VAMOC, EPOCA, and RETRO. VUA houses a series of high-end analytical instruments such as TIMS, rare gas mass spectrometer and 3 stable isotope IR-MS with carbonate/gas bench extraction/C-N-H analyser, an ICP-MS and HR-MC ICP-MS with laser ablation.

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