Modelling oceanic oxygen changes from the Holocene into the Anthropocene

We wish to investigate the processes driving past changes in Tropical Ocean oxygenation and to project future Tropical Ocean oxygen distributions until the end of this millennium. For the first time, transient (continuous, non-accelerated) simulations for the complete Holocene, starting about 10,000 calendar years BP, will be conducted with a focus on centennial to millennial timescale changes. This enables estimating the level of low- frequency natural variability in Tropical Ocean oxygenation, which is important in order to assess current and potential future trends. The joint analysis of model results, instrumental and paleo proxy data is a key element of our research project. The proposed work builds on the success of qualitatively reproducing reconstructed trends in ocean ventilation in the eastern tropical South Pacific (ETSP) by means of time slice experiments simulating the mid-Holocene and the preindustrial times. This region will remain our focus during the third phase of the SFB 754.

Multi-millennial simulations will be performed employing time-varying forcing (orbital, greenhouse gases) during the Holocene, to provide an estimate of natural centennial to millennial variability in dissolved oxygen in the ocean. Future projections of oxygen will be conducted covering the complete current millennium (i.e. until the year 3000) to study the long-term evolution of oxygen after stabilisation of atmospheric carbon dioxide in the 22nd century. This is important given the long adjustment timescale of ocean stratification, which is on the order of at least a millennium. Our studies will focus on the ocean circulation patterns driving natural oxygen variability and on the relative roles of dynamical and biogeochemical factors controlling variations in the spatial extent and intensity of oxygen minimum zones (OMZs). The regional focus on the ETSP is motivated by abundant modern and paleo proxy data of water mass structure and biogeochemical cycling complemented by new data to be obtained in the third phase (A5, A6).

A coherent synthesis of centennial to millennial variations in the ETSP-OMZ during the Holocene will be developed based on combining information from model experiments and the analysis of different proxy data. This knowledge will complement scenarios of future long-term climate variability and their impacts on the ETSP-OMZ. Our modelling efforts put the shorter timescale focus of other subprojects into a longer-term perspective. The proposed studies are a contribution to international model comparison initiatives (PMIP3 and CMIP6).

Bordbar, M.H., T. Martin, M. Latif and W. Park (2015) Long-Term Internal Variability Effects on 21st Century Dynamic Sea Level Projections. Nat. Clim. Change, doi: 10.1038/NCLIMATE2569

Cocco, V., F. Joos, M. Steinacher, T.L. Frölicher, L. Bopp, J. Dunne, M. Gehlen, C. Heinze, J. Orr, A. Oschlies, B. Schneider, J. Segschneider and J. Tjiputra (2013) Oxygen and indicators of stress for marine life in multi- model global warming projections. Biogeoscienes, 10, 1849-1868, doi: 10.5194/bg-10-1849-2013

Harlass, J., M. Latif and W. Park (2015) Improving climate model simulation of tropical Atlantic sea surface temperature: The importance of enhanced vertical atmosphere model resolution. Geophys. Res. Lett., 42, 2401-2408, doi: 10.1002/2015GL063310

Khon, V., W. Park, M. Latif, I. Mokhov and B. Schneider (2012) Tropical circulation and hydrological cycle response to orbital forcing. Geophys. Res. Lett., 39 (L15708), doi: 10.1029/2012GL052482

Latif, M., T. Martin and W. Park (2013) Southern Ocean Sector Centennial Climate Variability and Recent Decadal Trends. J. Climate, 19, 7767-7782, doi: 10.1175/JCLI-D-12-00281.1

Martin, T., W. Park and M. Latif (2013) Multi-centennial variability controlled by Southern Ocean convection in the Kiel Climate Model. Clim. Dynam., 40, 2005-2022, doi: 10.1007/s00382-012-1586-7

Meng, Q., M. Latif, W. Park, N.S. Keenlyside, V.A. Semenov and T. Martin (2012) Twentieth century Walker Circulation change: Data analysis and model experiments, Clim. Dynam., 38, 1757-1773, doi: 10.1007/ s00382-011-1047-8

Salau, O., B. Schneider, W. Park, V. Kohn and M. Latif (2012) Modeling the ENSO Impact of orbitally induced mean state climate changes. J. Geophys. Res., 117, (C05043), doi: 10.1029/2011JC007742

Zinke, J., M. Pfeiffer, W. Park, B. Schneider, L. Reuning, W.-Chr. Dullo, G.F. Camoin, A. Mangini, A. Schroeder- Ritzrau, D. Garbe-Schönberg and G.R. Davies (2014) Seychelles coral record of changes in sea surface temperature bimodality in the western Indian Ocean from the Mid-Holocene to the present. Clim. Dynam., doi: 10.1007/s00382-014-2082-z

Prof. B. Schneider                            Prof. Mojib Latif
Tel.: +49 431 880 3254                    Tel.: +49 431 600 4050
bschneider(a)             mlatif(a)