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• 1. [Article] Assessing the effects of ocean diffusivity and climate sensitivity on the rate of global climate change

  This is the publisher’s final pdf. The published article is copyrighted by Co-Action Publishing and can be found at: http://co-action.net/.

  Citation × Citation Citation Abstract Copy Title: Assessing the effects of ocean diffusivity and climate sensitivity on the rate of global climate change Author: Kothavala, Zavareh, Matthews, H. Damon, Ross, Andrew, Schmittner, Andreas This is the publisher’s final pdf. The published article is copyrighted by Co-Action Publishing and can be found at: http://co-action.net/. Title: Assessing the effects of ocean diffusivity and climate sensitivity on the rate of global climate change Author: Kothavala, Zavareh, Matthews, H. Damon, Ross, Andrew, Schmittner, Andreas This is the publisher’s final pdf. The published article is copyrighted by Co-Action Publishing and can be found at: http://co-action.net/. Close

• 2. [Article] A global model of the marine ecosystem for long-term simulations: Sensitivity to ocean mixing, buoyancy forcing, particle sinking, and dissolved organic matter cycling

  A new model of the marine ecosystem coupled into a global Earth System Climate Model suitable for long-term (multimillennial timescale) simulations is presented. The model is based on nitrate as the sole ...

  Citation × Citation Citation Abstract Copy Title: A global model of the marine ecosystem for long-term simulations: Sensitivity to ocean mixing, buoyancy forcing, particle sinking, and dissolved organic matter cycling Author: Eby, M., Giraud, X., Oschlies, Andreas, Schmittner, Andreas, Simmons, H. L. A new model of the marine ecosystem coupled into a global Earth System Climate Model suitable for long-term (multimillennial timescale) simulations is presented. The model is based on nitrate as the sole limiting nutrient. Prognostic equations for nutrients, phytoplankton, zooplankton, and detritus are solved online in the three-dimensional ocean circulation model component. Experiments with different parameterizations of vertical mixing, including a scheme of tidally driven mixing, changes in buoyancy forcing in the Southern Ocean, different particle sinking velocities, and the inclusion of dissolved organic matter are performed, and the results are compared with observations. The results reemphasize the roles of Southern Ocean freshwater forcing and diapycnal mixing in the low-latitude pycnocline in setting the global deep water circulation and properties. The influence of high mixing in the Southern Ocean as inferred from observations is much more limited. The deep water circulation also has a strong influence on the marine ecosystem and nutrient distributions. We demonstrate that larger values of vertical diffusion lead to a shallower nutricline due to increased upwelling. Export production and nutrient distributions respond sensitively to changes in mixing and to the ratio of particle sinking to remineralization in the upper ocean. The best fits to global measurements of temperature, salinity, deep ocean radiocarbon, mixed layer depth, nutrients, and chlorophyll are obtained for values of vertical mixing in the pycnocline of around 0.2–0.3 X 10-4 m2/s and for e-folding depth for particle remineralization of 100–200 m. A simple parameterization of dissolved organic matter dynamics increases primary production and nutrient concentrations in the upper ocean and improves chlorophyll distributions in the subtropical gyres but has no discernible influence on particulate export fluxes. Remaining model deficiencies are identified, and strategies for future model improvement are outlined. Title: A global model of the marine ecosystem for long-term simulations: Sensitivity to ocean mixing, buoyancy forcing, particle sinking, and dissolved organic matter cycling Author: Eby, M., Giraud, X., Oschlies, Andreas, Schmittner, Andreas, Simmons, H. L. A new model of the marine ecosystem coupled into a global Earth System Climate Model suitable for long-term (multimillennial timescale) simulations is presented. The model is based on nitrate as the sole limiting nutrient. Prognostic equations for nutrients, phytoplankton, zooplankton, and detritus are solved online in the three-dimensional ocean circulation model component. Experiments with different parameterizations of vertical mixing, including a scheme of tidally driven mixing, changes in buoyancy forcing in the Southern Ocean, different particle sinking velocities, and the inclusion of dissolved organic matter are performed, and the results are compared with observations. The results reemphasize the roles of Southern Ocean freshwater forcing and diapycnal mixing in the low-latitude pycnocline in setting the global deep water circulation and properties. The influence of high mixing in the Southern Ocean as inferred from observations is much more limited. The deep water circulation also has a strong influence on the marine ecosystem and nutrient distributions. We demonstrate that larger values of vertical diffusion lead to a shallower nutricline due to increased upwelling. Export production and nutrient distributions respond sensitively to changes in mixing and to the ratio of particle sinking to remineralization in the upper ocean. The best fits to global measurements of temperature, salinity, deep ocean radiocarbon, mixed layer depth, nutrients, and chlorophyll are obtained for values of vertical mixing in the pycnocline of around 0.2–0.3 X 10-4 m2/s and for e-folding depth for particle remineralization of 100–200 m. A simple parameterization of dissolved organic matter dynamics increases primary production and nutrient concentrations in the upper ocean and improves chlorophyll distributions in the subtropical gyres but has no discernible influence on particulate export fluxes. Remaining model deficiencies are identified, and strategies for future model improvement are outlined. Close

• 3. [Article] Climate Sensitivity Estimated From Temperature Reconstructions of the Last Glacial Maximum

  This is the author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the American Association for the Advancement of Science and can be found at: h...

  Citation × Citation Citation Abstract Copy Title: Climate Sensitivity Estimated From Temperature Reconstructions of the Last Glacial Maximum Author: Urban, Nathan M., Shakun, Jeremy D., Mahowald, Natalie M., Bartlein, Patrick J., Schmittner, Andreas, Clark, Peter U., Rosell-Mele, Antoni, Mix, Alan C. This is the author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the American Association for the Advancement of Science and can be found at: http://www.sciencemag.org/. Title: Climate Sensitivity Estimated From Temperature Reconstructions of the Last Glacial Maximum Author: Urban, Nathan M., Shakun, Jeremy D., Mahowald, Natalie M., Bartlein, Patrick J., Schmittner, Andreas, Clark, Peter U., Rosell-Mele, Antoni, Mix, Alan C. This is the author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the American Association for the Advancement of Science and can be found at: http://www.sciencemag.org/. Close

• 4. [Article] Simulating the global distribution of nitrogen isotopes in the ocean

  We present a new nitrogen isotope model incorporated into the three-dimensional ocean component of a global Earth system climate model designed for millennial timescale simulations. The model includes ...

  Citation × Citation Citation Abstract Copy Title: Simulating the global distribution of nitrogen isotopes in the ocean Author: Somes, Christopher J., Lehmann, Moritz F., Bourbonnais, Annie, Eby, Michael, Schmittner, Andreas, Altabet, Mark A., Galbraith, Eric D., Mix, Alan C., Montoya, Joseph P., Letelier, Ricardo M. We present a new nitrogen isotope model incorporated into the three-dimensional ocean component of a global Earth system climate model designed for millennial timescale simulations. The model includes prognostic tracers for the two stable nitrogen isotopes, 14N and 15N, in the nitrate (NO3−), phytoplankton, zooplankton, and detritus variables of the marine ecosystem model. The isotope effects of algal NO3− uptake, nitrogen fixation, water column denitrification, and zooplankton excretion are considered as well as the removal of NO3− by sedimentary denitrification. A global database of δ15NO3− observations is compiled from previous studies and compared to the model results on a regional basis where sufficient observations exist. The model is able to qualitatively and quantitatively reproduce many of the observed patterns such as high subsurface values in water column denitrification zones and the meridional and vertical gradients in the Southern Ocean. The observed pronounced subsurface minimum in the Atlantic is underestimated by the model presumably owing to too little simulated nitrogen fixation there. Sensitivity experiments reveal that algal NO3− uptake, nitrogen fixation, and water column denitrification have the strongest effects on the simulated distribution of nitrogen isotopes, whereas the effect from zooplankton excretion is weaker. Both water column and sedimentary denitrification also have important indirect effects on the nitrogen isotope distribution by reducing the fixed nitrogen inventory, which creates an ecological niche for nitrogen fixers and, thus, stimulates additional N2 fixation in the model. Important model deficiencies are identified, and strategies for future improvement and possibilities for model application are outlined. Title: Simulating the global distribution of nitrogen isotopes in the ocean Author: Somes, Christopher J., Lehmann, Moritz F., Bourbonnais, Annie, Eby, Michael, Schmittner, Andreas, Altabet, Mark A., Galbraith, Eric D., Mix, Alan C., Montoya, Joseph P., Letelier, Ricardo M. We present a new nitrogen isotope model incorporated into the three-dimensional ocean component of a global Earth system climate model designed for millennial timescale simulations. The model includes prognostic tracers for the two stable nitrogen isotopes, 14N and 15N, in the nitrate (NO3−), phytoplankton, zooplankton, and detritus variables of the marine ecosystem model. The isotope effects of algal NO3− uptake, nitrogen fixation, water column denitrification, and zooplankton excretion are considered as well as the removal of NO3− by sedimentary denitrification. A global database of δ15NO3− observations is compiled from previous studies and compared to the model results on a regional basis where sufficient observations exist. The model is able to qualitatively and quantitatively reproduce many of the observed patterns such as high subsurface values in water column denitrification zones and the meridional and vertical gradients in the Southern Ocean. The observed pronounced subsurface minimum in the Atlantic is underestimated by the model presumably owing to too little simulated nitrogen fixation there. Sensitivity experiments reveal that algal NO3− uptake, nitrogen fixation, and water column denitrification have the strongest effects on the simulated distribution of nitrogen isotopes, whereas the effect from zooplankton excretion is weaker. Both water column and sedimentary denitrification also have important indirect effects on the nitrogen isotope distribution by reducing the fixed nitrogen inventory, which creates an ecological niche for nitrogen fixers and, thus, stimulates additional N2 fixation in the model. Important model deficiencies are identified, and strategies for future improvement and possibilities for model application are outlined. Close