DCESS five year report
During our five year term we made major advances in all these areas. These advances are documented in publications in some of the best international scientific journals (see publication list). For example, since the beginning of 2000, 8 of our papers (5 with DCESS first authors) were published in Nature or Science and 12 of our papers (8 with DCESS first authors) were published in Geophysical Research Letters or Geology. In all, we had 21, 26 and 29 international publications in the years 2000, 2001 and 2002.
In the short time after its inception DCESS gained an international reputation in Earth System Science (ESS). Thus, in a lead editorial in Science (June 15, 2001), DCESS is mentioned among only five other (and older) institutes as one of a "...mere handful of U.S. and European institutions (that) offer graduate programs and the kind of interdisciplinary working environments that are essential for the rapid development of ESS". The author, Professor John Lawton from Imperial College and chief executive of the Natural Environment Research Council of the United Kingdom, concluded, "…It is hard to imagine a more important discipline than Earth System Science. We urgently need to overhaul our thinking and rejig our institutions to allow this crucial new science to flourish.”
DCESS was organized from the start into our main research areas to provide focus, but also to put in place pillars of research strength upon which to base new, often cross-disciplinary, initiatives. As noted in a December 2001 report of the Evaluation Committee of DCESS, we “fulfilled the goals outlined in the original research plan for the period 1997-2002” and our research “has progressed on a wide variety of sub-themes…with no significant deviation from the plan”. The Committee noted the quality and importance of our research (“first-rate group of researchers”, “cutting edge of earth science”, “pioneering work”, “measurements are unique” in “an important, unexplored area”) and was impressed with “exceptionally talented and energetic students and post-doctoral fellows” and with “the center as a research training environment”.
We identified and corroborated a dynamical stabilizing mechanism for free perturbations in the climate system based on atmospheric angular momentum (AM) transport and its link to surface winds and evaporation. Latent heat from evaporation is carried from the surface and released above the main water vapour layers from where it can be effectively radiated to space. Without this convective bypassing of the main greenhouse absorbers, sea surface temperature would be unstable at its present equilibrium because of the water vapour/infrared radiative (WVIR) feedback, whereby downwelling infrared radiation at the surface from the atmospheric water vapour increases faster with temperature than the upwelling Stefan-Boltzmann radiation from the surface.
The operation of the above stabilizing mechanism was demonstrated using a simple hemispheric, atmosphere-ocean model with the surface energy budget processes parameterized using observations (Bates, 1999). An analytical solution for free perturbations of small amplitude about the model's equilibrium climate revealed the AM/evaporative stabilizing mechanism, showing it to be strong enough to counteract the destabilizing influence of the WVIR feedback. Both the Clausius-Clapeyron and ventilation components of the evaporative perturbations contributed to the stabilizing effect. In an extension of the surface energy budget model to include a simple ocean thermohaline circulation, this circulation was found to be more stable than indicated by models of the Budyko-Sellers kind with a top-of-the-atmosphere approach to the energy parameterizations. Simulations with another simple ocean-atmosphere model showed that the thermohaline circulation and climate depend strongly on ocean vertical and horizontal exchange (including the effects of the wind-driven circulation), providing negative feedbacks to stabilize climate (Shaffer and Olsen, 2001).
We performed atmospheric general circulation model (GCM) experiments to test the validity of the AM/evaporative stabilizing mechanism (Alexeev and Bates, 1999). A uniform 2ºC perturbation to the equilibrium sea surface temperature was applied on an aquaplanet. Evaporation increased as a result of the perturbation, due both to the Clausius-Clapeyron factor and the ventilation factor associated with increased AM transport. As in the simple model, the evaporative stabilizer was strong enough to counteract the destabilizing WVIR feedback. We also carried out a global data study using 40 years of the NCEP/NCAR Reanalysis to test the validity of the parameterizations underlying the dynamical stabilizing mechanism and found the parameterizations to be valid on time scales of a year or longer. We constructed a single column model of the tropical atmosphere in which the humidity profile was allowed to vary internally and the surface wind was allowed to vary in accordance with our AM relationship (Caballero, 2001). Here also it was found that the Clausius-Clapeyron and ventilation factors in evaporation were sufficient to keep the model stable in the face of the WVIR feedback.
We also studied the sensitivity of the climate system to a CO2 doubling using the simple energy balance approach with AM-induced winds described above (Bates, 2003). Although the ventilation factor in evaporation is stabilizing for free perturbations, it was found to act as a positive feedback (increasing the warming) for forced perturbations if these are sufficiently weighted towards the extratropics. For realistic magnitude and distribution of the surface forcing, the simple model gives a warming for a CO2 doubling comparable to that given by GCMs. In these circumstances, the ventilation feedback more than doubles the hemispheric average warming. The positive feedback effect of the ventilation term in the sensitivity context (for a CO2 doubling) has been corroborated by GCM experiments (Alexeev, 2003).
The oceans influence the environment and climate on Earth by storing and transporting heat and fresh water, and by modulating the composition of greenhouse gases like CO2 in the atmosphere. We carried out modeling and observational studies to address the role of the ocean in this context. Many of these results mesh with those cited above and below from our other two research areas.
Global ocean experiments with the Modular Ocean Model, developed at
To address ocean biogeochemical cycling and its influence on atmospheric CO2 levels, we also used a suite of simple to complex models, ranging from the simple High Latitude exchange/Diffusion-Advection (HILDA) model (Shaffer, Bendtsen and Ulloa, 1999), over intermediate complexity models (Brovkin et. al., 2002) to 3-D ocean GCM’s. In the HILDA work we found a significant, 20 ppm lowering of atmospheric CO2 levels due to fractionation during remineralization of organic matter in the ocean, as determined from our analysis of global ocean data. In the GCM work, a new microbial loop for dissolved organic carbon (DOC) cycling in the water column, based on joint field studies (see below) and laboratory experiments, was implemented to model global ocean distributions of DOC. Results compared favorably with observed DOC gradients through the deep ocean, supporting the validity of the proposed loop.
Our field studies and data analyses were focused mainly on the eastern
Work in the northern
Chemical traces of microbial activity are preserved in the fossil record. These indicate the presence, or even dominance, of particular metabolisms, and provide clues to the chemistry of the Earth surface environment. Our focus has been mostly on sulfur, as sulfur-metabolizing organisms fractionate sulfur isotopes to an extent depending on environmental variables such as seawater sulfate and atmospheric oxygen levels. Also, the isotopic composition of sedimentary sulfides provides a record of ancient microbial activity over geologic time.
We have undertaken extensive studies on the ability of sulfur-metabolizing organisms to fractionate under conditions that may have existed in the geologic past. Thus, we have documented high fractionations associated with sulfate reduction at temperatures up to 88oC for natural populations of sulfate reducers collected with the deep sea submersible Alvin from an active hydrothermal vent field (Canfield et al., 2000), and for natural populations of hyperthermophilic sulfate reducers. We have also studied fractionation of natural populations of sulfate reducers at modern surface temperatures (Habicht and Canfield, 2001; Canfield, 2001) and fractionations associated with the disproportionation of So under sedimentary conditions (Böttcher and Thamdrup, 2001). Furthermore, we have explored the ability of a wide variety different sulfate reducers to fractionate at low sulfate concentrations, in the range we believe appropriate for ancient Precambrian oceans. From these studies we conclude that the ocean before 2.5 billion years ago contained over 100 times less sulfate than the present ocean (Habicht et al., 2002). This would have led to considerable sediment methanogenesis allowing for a strong source of greenhouse gas to the early Earth atmosphere. From these studies, and some of those described below, we can begin to trace the history of Earth surface oxidation and to understand some of the processes controlling this history.
We have examined the isotopic composition of sulfur species in sediments collected from the 3.5 billion yr. old North Pole barite deposits of
We used a simple ocean-atmosphere model to demonstrate the plausibility of an extended period of sulfidic ocean bottom water conditions from around 1.8 to 0.8 billion years ago (Canfield, 1998). A sulfidic ocean is consistent with atmospheric oxygen levels < 25% of present-day, and some recent evidence from our group supports this model (Shen et al., 2002). This model is gaining general acceptance and has spurred further studies exploring how the sulfidic ocean might have influenced the pace of eukaryote evolution (Anbar and Knoll, Science, v. 297, 1137-1142). We have used the composition of Archean and early Proterozoic (< 2.0 billion years ago) banded iron formations to constrain ancient ocean phosphate concentrations to around 10 percent of present-day (Bjerrum and Canfield, 2002). Low phosphate concentrations would have meant low rates of primary production, providing an explanation for the generally low concentrations of atmospheric oxygen at this time.
Other highlights include the first demonstration in nature of anaerobic ammonia oxidation with nitrate which produces N2 gas and is therefore a sink for fixed nitrogen in the environment (Thamdrup and Dalsgaard, 2003). This process could have global significance as we have found that it occurs actively in the anoxic water column of a marine basin with chemical characteristics very similar to the oxygen minimum zones of the world's oceans (Dalsgaard et al., 2003). Indeed, the anammox process could be responsible for 20 to 30 percent of the total loss of nitrogen from the global ocean.
Internationally, we highlight our special relationship and close cooperation with the Program for Physical Oceanography and Climate,
We communicated our research results primarily through publication in international journals (see publication list) and through talks and posters at international conferences (see our yearly reports at www.dcess.dk/PublicFrm.htm). We also hosted three workshops with international attendance. We placed great value on informing the public and the press about our activities. DCESS research was highlighted in a number of articles in Danish national newspapers and professional and popular journals like Berlingske Tidende and Ingeniøren, and we have been interviewed in local and national radio news broadcasts. Our work was recently highlighted (Feb. 11, 2003) in the Science Program Viden Om, broadcast nationally on DR2. Furthermore, international newspapers like the New York Times and the Sydney Morning Herald reported on our results and our work also appeared in articles in Science News and Scientific American. We contributed to a book on climate from the Danish Meteorological Institute and presented our work at university open house arrangements, at the Danish Natural Science Festival, at schools, and in continuing education programs like the Folkeuniversitetet. DCESS associates also served on several editorial boards of both scientific and popular journals and convened a number of sessions at international symposia.
DCESS associates were actively engaged in teaching and research training at beginning undergraduate to advanced graduate levels at our host universities, including courses in biology, ecology, oceanography and meteorology. One course, "The History of Life", at
In a decision letter of February 2002, the Danish National Research Foundation decided not to grant a new five-year term to DCESS. However, more modest funds were offered over three years to “embed” DCESS activities into our respective host institutes. This was carried out with success in
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Alexeev, V. and Bates, J.R. (1999) GCM experiments to test a proposed dynamical stabilizing mechanism in the climate system. Tellus, 51A, 630‑651.
Alexeev, V.A (2003) Sensitivity to CO2 doubling of an atmospheric GCM coupled to an oceanic mixed layer. Climate Dynamics, 20, 775-787.
Bendtsen, J. and Bjerrum, C. (2002) Vulnerability of climate on Earth to sudden changes in insolation. Geophysical Research Letters, 15, 10.1029/2002GL014829.
Bjerrum, C.J., Surlyk, F., Callomon, J.H., and Slingerland, R.L. (2001) Numerical paleoceanographic study of the early Jurassic Transcontinental Laurasian Seaway. Paleoceanography, 16, 390-404.
Bjerrum, C. and Canfield, D.E. (2002) Ocean productivity before about 1.9 Gyr ago limited by phosphorus adsorption onto iron oxides. Nature, 417, 159-162.
Brandt, P., Rubino, A., Quadfasel, D.R., Alpers, W., Sellschopp, J. and Fiekas, H.V. (1999) Evidence for the influence of Atlantic‑Ionian stream fluctuation on the tidally induced internal dynamics in the Strait of Messina. Journal of Physical Oceanography, 29, 1071‑1080.
Brandt, P., Stramma L., Schott F.A., Fischer J., Dengler M. and Quadfasel D.R. (2002) Annual Rossby waves in the Arabian Sea from TOPEX/POSEIDON altimeter and in situ data. Deep-Sea Research II, 49, 1197-1210.
Brovkin, V., Hofman, M., Bendtsen, J. and Ganopolski, A. (2002) Ocean biology could control atmospheric d13C during glacial-interglacial cycle. Geochemistry, Geophysics, Geosystem, 3, 10.1029/2001GC000270.
Caballero, R. and Sutera, A. (2000) Equilibration of a simple baroclinic flow in a ß channel and on the sphere. Journal of Atmospheric Sciences, 57, 3296‑3314.
Caballero, R. (2001) Surface wind, subcloud humidity and the stability of the tropical climate. Tellus, 53A, 513-525.
Caballero, R., Jewson, S. and Brix, A. (2002) Long memory in surface air temperature: Detection, modeling, and application to weather derivative valuation. Climate Research, 21, 127-140.
Caballero R. and Lavagnini A. (2002) A numerical study of the sea breeze, slope winds and convergence lines around Rome. Nuovo Cimento, C 25, 287-304.
Canfield, D.E., Boudreau, B.P., Mucci, A. and Gundersen, J. (1998) The early diagenetic formation of organic sulfur in the sediments of
Canfield, D. E., Thamdrup, B. and S. Fleischer (1998) Isotope fractionation and sulfur metabolism by pure and enrichment cultures of elemental sulfur disproportionating bacteria. Limnology and Oceanography, 43, 253-264.
Canfield, D.E. (1998) A new model for Proterozoic ocean chemistry, Nature, 396, 450‑453.
Canfield, D.E. and Raiswell, R. (1999) The evolution of the sulfur sycle. American Journal of Science, 299, 607‑723.
Canfield, D.E. (1999) A breath of fresh air. Nature, 400, 503‑504.
Canfield, D.E., Habicht, K.S. and Thamdrup, B. (2000) The Archean sulfur cycle and the early history of atmospheric oxygen. Science, 288, 658‑661.
Canfield, D.E. (2001) Isotope fractionation by natural populations of sulfate-reducing bacteria. Geochimica et Cosmochimica Acta, 65, 1117-1124.
Canfield, D.E. (2001) Biogeochemistry of sulfur isotopes. In Stable Isotope Geochemistry, Reviews in Mineralogy & Geochemistry,43, 607‑636.
Claussen, M., Mysak, L.A., Weaver, A.J., Crucifix, M., Fichefet, T., Loutre, M.F., Weber, S.L., Alcamo ,J., Alexeev, V., Berger, A., Calov, R., Ganopolski A., Goosse, H., Lohman, G., Lunkeit, F., Mokhov, I., Petoukhov, V., Stone, P. and Wang, Z. (2002) Earth system models of intermediate complexity: closing the gab in the spectrum of climate system models. Climate Dynamics, 18, 579-586.
Dalsgaard, T. and Thamdrup, B. (2002) Factors controlling anaerobic ammonium oxidation with nitrite in marine sediments. Applied and Environmental Microbiology. 68, 3802-3808.
Dalsgaard, T., Canfield, D.E., Petersen, J., Thamdrup, B. and Acuña-González, J. (2003) N2 production by the anammox reaction in the anoxic water column of
Dengler, M., Quadfasel, D.R., Schott, F.A. and Fischer, J. (2002) Abyssal circulation in the Somali Basin. Deep-Sea Research II, 49, 1297-1322.
Dengler, M. and Quadfasel, D.R. (2002) Equatorial Deep Jets and abyssal mixing in the Indian Ocean. Journal of Physical Oceanography, 32, 1165-1180.
Detmers, J, Brüchert, V., Habicht, K.S. and Kuever, J. (2001) Diversity of sulfur isotope fractionation by sulfate‑reducing prokaryotes. Applied and Environmental Microbiology, 67, 888-894.
Eigenheer, A. and Quadfasel, D.R. (2000) Seasonal variability of the
Falkowski, P., Scholes, R.J., Boyle, E., Canadell, J., Canfield, D.E., Elser, J., Gruber, N., Hibbard, K., Högberg, P., Linder, S., Mackenzie, F.T., Moore III, B., Pedersen, T., Rosenthal, Y., Seitzinger, S., Smetacek, V. and Steffen, W. (ICBP Carbon Working Group). (2000) The global carbon cycle: A test of our knowledge of Earth as a system. Science, 290, 291‑296.
Finster, K., Liesack, W. and Thamdrup, B. (1998) Elemental sulfur and thiosulfate dispropotionation by Desulfocapsa sulfoexigens sp. nov., a new anaerobic bacterium isolated from marine surface sediment, Applied and Environmental Microbiology, 64, 119‑125.
Fones, G.R., Davison, W., Holby, O., Jørgensen, B.B. and Thamdrup, B. (2001) High‑resolution metal gradients measured by In Situ DGT/DET deployment in Black Sea sediments using an autonomous benthic lander. Limnology and Oceanography, 46, 982-988.
Garric, G., Douville, H. and Déqué, M. (2002) Prospects for improved seasonal predictions of monsoon precipitations over Sahel. International Journal of Climatology, 22, 331-345.
Glud, R.N., Holby, O., Hoffmann, F. and Canfield, D.E. (1998) Benthic mineralisation and exchange in Artic sediments (
Glud, R.N., Risgaard‑Petersen, N., Thamdrup, B., Fossing, H. and Rysgaard S. (2000) Benthic carbon mineralization in a high‑Arctic sound (Young Sound, NE‑Greenland). Marine Ecology Progress Series, 206, 59‑71.
Grotefendt, K., Logemann, K., Quadfasel, D. and Ronski, S. (1998) Is the
Habicht, K.S., and Canfield, D.E. (1997) Sulfur isotope fractionation during bacterial sulfate reduction in organic rich sediments. Geochimica et Cosmochimica Acta, 61, 5351-5361.
Habicht, K.S., Canfield, D.E., and Rethmeier, J. (1998) Sulfur isotope fractionation during bacterial reduction and disproportionation of thiosulfate and sulfite, Geochimica et Cosmochimica, 62, 2585‑2595.
Habicht, K.S. and Canfield D.E. (2001) Isotope fractionation by sulfate‑reducing natural populations and the isotopic composition of sulfide in marine sediments. Geology, 29, 555-558.
Habicht, K.S., Gade, M., Thamdrup, B., Berg, P. and Canfield, D.E. (2002) A calibration of sulfate levels in the Archean Ocean. Science, 298, 2372-2374.
Hansen, J.W., Thamdrup, B. and Jørgensen, B.B. (2000) Anoxic incubation of sediment in gas‑tight plastic bags: a method for biogeochemical process studies. Marine Ecology Progress Series, 208, 73‑280.
Hesselbo, S.P., Gröcke, D.R., Jenkyns, H.C., Bjerrum, C.J., Ferrimond, P.,
Hormazabal, S., Shaffer, G., Letelier, J. and Ulloa, O. (2001) Local and remote forcing of sea surface temperature in the coastal upwelling system off
Hormazabal, S., Shaffer G. and Pizarro O. (2002) Tropical Pacific control of intraseasonal oscillation off Chile by way of oceanic and atmospheric pathways. Geophysical Research Letters, 29, 10.1029/2001GL013481.
Huber, M. and Caballero. R. (2003) Eocene El Niño: evidence for robust tropical dynamics in the “hothouse”. Science, 299, 877-881.
Høyer, J.L.and Quadfasel, D. (2001) Detection of deep overflows with satellite altimetry. Geophysical Research Letters, 28, 1611-1614.
Høyer, J.L., Quadfasel D. and Andersen O.B. (2002) Deep ocean currents detected with satellite altimetry. Canadian Journal of Remote Sensing, 28, 556-566.
Jørgensen, B. B., Weber, A., and Zopfi, J. (2001) Sulfate reduction and anaerobic methane oxidation in
Karstensen, J. and Quadfasel, D.R. (2002) On the formation of Southern Hemisphere thermocline waters: Water mass conversion and subduction. Journal of Physical Oceanography, 32, 3020-3038.
Karstensen, J. and Quadfasel ,D.R. (2002) Water subducted into the Indian Ocean Subtropical gyre. Deep-Sea Research II, 49, 1441-1457.
Konhauser, K.O., Hamade T., Raiswell R., Morris R.C., Ferris F.G., Southam G. and Canfield D.E. (2002) Could bacteria have formed the Precambrian iron formations? Geology, 30, 1079-1082.
Kostka, J.E., Thamdrup, B., Glud, N.R., and Canfield, D.E. (1999) Rates and pathways of carbon oxidation in permently cold Artic sediments. Marine Ecology Progress Series,180, 7-21.
Krom, M.D., Mortimer R.J.M., Poulton S.W., Hayes P., Davies I.M., Davison W. and Zhang H. (2002) In-situ determination of dissolved iron production in recent marine sediments Aquatic Sciences, 64, 282-291.
Körtzinger, A., Mintrop, L., Wallace, D.W.R., Johnson, K.M., Neill, C., Tilbrook, B, Towler, P., Inoue, H., Ishii, M., Shaffer, G., Torres, R.F., Ohtaki, E., Yamashita, E., Poisson, A., Brunet, C., Schauer, B., Goyet, C. and Eischeid, G. (2000) The International at‑sea Intercomparison of fCO2 systems during the R/V Meteor cruise 36/1 in the North Atlantic. Ocean. Marine Chemistry, 72, 171‑192.
Leth, O. K. and Shaffer, G. (2001) A numerical study of seasonal variability of circulation off central
Lherminier, P., Gascard, J.C. and Quadfasel, D.R. (1999) The Greenland Sea in winter 1993 and 1994: preconditioning for deep convection. Deep‑Sea Research II, 46, 1199‑1235.
Li, Y., Ménard, R., Riishøjgaard, L.P., Cohn, S.E. and Rood, R.B. (1998) A study on assimilating potential vorticity data. Tellus, 50A, 490‑506.
Li, Y., Ruge, J., Bates, J.R. and Brandt, A. (2000) A proposed adiabatic formulation of 3‑dimensional global atmospheric models based on potential vorticity. Tellus, 52A, 129‑139.
Lindberg, K. and Alexeev, A. (2000) A study of the spurious orographic resonance in semi‑implicit semi‑Lagrangian models. Monthly Weather Review, 128, 1982‑1989.
Morales, C.E., Hormazábal, S. and Blanco, J.L. (1999) Interannual variability in the mesoscale distribution of the depth of the upper boundary of the oxygen minimum layer off northern
Onstad, G.D., Canfield, D.E., Quay, P.D. and Hedges, J.I. (2000) Sources of particulate organic matter in rivers from the continental
Pizarro, O. and Shaffer, G. (1998) Wind‑driven, coastal‑trapped waves off the island of
Pizarro, O., Shaffer, G., Dewitte, B. and Ramos, M. (2002) Dynamics of seasonal and interannual variability of the Peru-Chile Undercurrent. Geophysical Research Letters, 29, 10.1029/2002GL014790.
Poulton, S.W. and Raiswell, R. (2002) The low-temperature geochemical cycle of iron: From continental fluxes to marine sediment deposition. American Journal of Science, 302, 774-805.
Poulton, S.W., Krom, M.D., Van Rijn, J. and Raiswell, R. (2002) The use of hydrous iron (III) oxides for the removal of hydrogen sulphide in aqueous systems. Water Research, 36, 825-834
Quadfasel, D. (2001) Ocean Currents:
Raiswell, R. and Canfield, D.E. (1998) Sources of iron for pyrite formation in marine sediments, American Journal of Science, 298, 219‑245.
Renwie, L., Chen, J., Zhang, S., Lei, J., Shen, Y. and
Reppin, J., Schott, F.A., Fischer, J. and Quadfasel, D.R., (1999) Equatorial currents and transports in the upper central Indian Ocean: Annual cycle and interannual variability. Journal of Geophysical Research, 104, 15,495‑15,514.
Riishøjgaard, L.P., Cohn, S.E., Li, Y. and Ménard, R. (1998) The use of spline interpolation in semi‑Lagrangian, transport models. Monthly Weather Review, 126, 2008‑2016.
Roselló‑Mora, R., Thamdrup, B., Schäfer, H., Weller, R. and Amann, R. (1999) Marine sediment microbial community response to organic carbon ammendation under anaerobic conditions. Systematic and Applied Microbiology, 22, 237‑248.
Rudels, B., Friedrich, H.J. and Quadfasel, D. (1999) The Arctic Circumpolar Boundary Current. Deep‑Sea Research II, 46, 1023‑1062.
Rudels, B., Meyer, R., Farhbach, E., Ivanov, I.I., Østershus, S., Quadfasel, D., Schauer, U., Tverberg, V. and Woodgate, R.A. (2000) Water mass distribution in
Ruge, J.W., Li, Y., McCormick, S., Brandt A. and Bates, J.R., (2000) A nonlinear multigrid solver for a semi‑Lagrangian potential vorticity‑based shallow water model on the sphere.
Rysgaard, S., Thamdrup, B., Risgaard‑Petersen, N., Fossing, H., Berg, P., Christensen, P.B. and Dalsgaard, T. (1998) Seasonal carbon and nutrient mineralization in a high‑Arctic coastal marine sediment, Young Sound, Northeast Greenland. Marine Ecology Progress Series, 175, 261‑276.
Rysgaard, S., Fossing, H. and Jensen, M.M. (2001) Organic matter degredation through oxygen respiration, denitrification, and manganese, iron and sulfate reduction in marine sediments (Kattegat and Skagerrak). Ophelia, 55, 77-91.
Shaffer, G., Bendtsen, J. and Ulloa O. (1999) Fractionation during remineralization of organic matter in the ocean. Deep‑Sea Research I, 46, 185‑204.
Shaffer, G., Hormazabal, S., Pizarro, O. and
Shaffer, G., Leth, O., Ulloa, O., Bendtsen, J., Daneri, G., Dellarossa, V., Hormazábal, S. and Sehlstedt, P.‑I. (2000) Warming and circulation change in the eastern
Shaffer, G. and Olsen, S.M. (2001) Sensitivity of the thermohaline circulation and climate to ocean exchanges in a simple coupled model. Climate Dynamics, 17, 433-444.
Shen, Y., Zhao, R., Chu, X. and Lei, J. (1998) The carbon and sulfur isotope signatures in the Precambrian‑Cambrian transition series of the Yangtze Platform, Precambrian Research, 89, 77‑86.
Shen, Y. and Schidlowski, M. (2000) New C isotope stratigraphy from southwest
Shen, Y., Schidlowski, M. and
Shen, Y., Buick, R. and Canfield, D. (2001) Isotopic evidence for microbial sulphate reduction in the early Archean. Nature, 410, 77-81.
Shen Y., Canfield D.E. and Knoll A.H. (2002) Middle Proterozoic ocean chemistry: Evidence from the
Sonnerup, R.E., Quay, P.D., McNichol, A.P., Bullister, J.L., Westby, T.A. and Anderson, H.L. (1999) Reconstructing the oceanic 13C Suess effect. Global Biogeochemical Cycles, 13, 857‑872.
Sonnerup, R.E., Quay, P.D. (2000) The Indian Ocean 13C Suess effect. Global Biogeochemical Cycles, 14, 903‑916.
Sonnerup, R.E. (2001) On the relations between CFC derived water mass ages. Geophysical Research Letters, 28, 1739-1742.
Stramma, L., Brandt, P., Schott, F.A., Quadfasel, D. and Fischer, J. (2002) Winter and summer monsoon water mass, heat and freshwater transport changes in the Arabian Sea near 8ºN. Deep-Sea Research II, 49, 1173-1195.
Sørensen, J. V. T., Ribbe, J. and Shaffer, G. (2001) On Antarctic Intermediate Water mass formation in Ocean General Circulation Models. Journal of Physical Oceanography,31, 3295-3311.
Sørensen, K. B., Finster, K. and Ramsing, N. B. (2001) Thermodynamic and kinetic requirements in anaerobic methane oxidizing consortia exclude hydrogen, acetate, and methanol as possible electron shuttles. Microbial Ecology,42, 1‑10.
Teske, A., Ramsing, N.B., Habicht, K.S., Fukui, M., Küver, J., Jørgensen, B.B. and Cohen, Y. (1998) Sulfate-reducing bacteria and their activities in cyanobacterial mats of Solar Lake (Sinai, Egypt). Applied and Environmental Microbiology, 64, 2943-2951.
Thamdrup, B., Hansen, J.W. and Jørgensen, B.B. (1998) Temperature dependence of aerobic respiration in a coastal sediment, FEMS Microbiology Ecol., 25, 189‑200.
Thamdrup, B. and Fleischer, S. (1998) Temperature dependence of oxygen respiration, nitrogen mineralization, and nitrification in Arctic sediments, Aquatic Microbial Ecology, 15, 191‑199.
Thamdrup, B. (2000) Microbial manganese and iron reduction in aquatic sediments. Advances in Microbial Ecology, 16, 41‑84.
Thamdrup, B. and Dalsgaard, T. (2000) The fate of ammonium in manganese oxide‑rich sediment. Geochimica et Cosmochimica Acta, 64, 4157‑4164.
Thamdrup, B., Rosselló‑Móra, R. and Amann, R. (2000) Microbial manganese, iron and sulfate reduction in
Thamdrup B. and Dalsgaard T. (2002) Production of N2 through anaerobic ammomium oxidation coupled to nitrate reduction in marine sediments. Applied & Environmental Microbiology, 68, 1312‑1318.
Ulloa, O., Escribano, R.,Hormazabal , S., Quiñones, R., Gonzalez, R. and Ramos, M. (2001) Evolution and biological effects of the 1997-1998 El Niño in the upwelling ecosystem off northern
Williams, M.J.M. (2001) Application of a three‑dimensional numerical model to
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Technical and administrative staff
UC: University of Copenhagen/Department of Geophysics
NRC/US: National Research
SNF: Danish Natural Science Research Council
EU: European Union