Abstract. The Southern Ocean has been identified as a key player for the global atmospheric temperature and pCO 2 rise across the last glacial termination. One leading hypothesis for explaining the initial pCO 2 step of 38 ppm (Mystery Interval 17.5−14.5 ka) is enhanced upwelling of Southern Ocean deep water that had stayed isolated from surface layers for millennia, thereby accumulating carbon from remineralisation of organic matter. However, the individual influences involved in this interplay of processes are not fully understood. A credible explanation for this remarkable climate change must also be able to
Abstract. Interactions between the land biosphere and the atmosphere play an important role for the Earth's carbon cycle and thus should be considered in studies of global carbon cycling and climate. Simple approaches are a useful first step in this direction but may not be applicable for certain climatic conditions. To improve the ability of the reduced-complexity Danish Center for Earth System Science (DCESS) Earth system model DCESS to address cold climate conditions, we reformulated the model's land biosphere module by extending it to include three dynamically varying vegetation zones as well as a permafrost component. The vegetation zones are formulated by emulating the behaviour of a complex land biosphere model. We show that with the new module, the size and timing of carbon exchanges between atmosphere and land are represented more realistically in cooling and warming experiments. In particular, we use the new module to address carbon cycling and climate change across the last glacial transition. Within the constraints provided by various proxy data records, we tune the DCESS model to a Last Glacial Maximum state and then conduct transient sensitivity experiments across the transition under the application of explicit transition functions for high-latitude ocean exchange, atmospheric dust, and the land ice sheet extent. We compare simulated time evolutions of global mean temperature, pCO 2 , atmospheric and oceanic carbon isotopes as well as ocean dissolved oxygen concentrations with proxy data records. In this way we estimate the importance of different processes across the transition with emphasis on the role of land biosphere variations and show that carbon outgassing from permafrost and uptake of carbon by the land biosphere broadly compensate for each other during the temperature rise of the early last deglaciation.
Correspondence to: Roland Eichinger (roland@dgf.uchile.cl)
S1 IntroductionThis supplement provides additional material to the article "An improved land biosphere module for use in reduced complexity ESMs with application to the last glacial termination". We provide a detailed description of our treatment of the new vegetation dependent albedo, the dust radiative forcing and high latitude ocean iron-limitation and present an example case for the snow and ice line parameterisation that interacts with the new biosphere scheme. Next, we give the mathematical description of the 5 ocean vertical diffusion profile function in the high latitude model ocean that is applied for generating Last Glacial Maximum (LGM) conditions in the DCESS model and the formulation of the resumption of deep ocean mixing. Furthermore, we present some additional information on the generation of model LGM conditions in atmosphere and ocean, a literature review on the Mystery Interval (MI) and an overview for model and proxy data changes during the MI. The Supplement ends with additional information on the various 14 C production rate time series that were applied in the model simulations, an analysis of the DCESS 10 model calculated 14 C production rate time series and the isotope ratio definitions. S1
Interactions between the land biosphere and the atmosphere play an important role for the Earth's carbon cycle and thus should be considered in studies of global carbon cycling and climate. Simple approaches are a useful first step in this direction but may not be applicable for certain climatic conditions. To improve the ability of the reduced-complexity Danish Center for Earth System Science (DCESS) Earth System Model DCESS to address cold climate conditions, we reformulated the 5 model's land biosphere module by extending it to include three dynamically varying vegetation zones as well as a permafrost component. The vegetation zones are formulated by emulating the behavior of a complex land biosphere model. We show that with the new module, the size and timing of carbon exchanges between atmosphere and land are represented more realistically in cooling and warming experiments. In particular, we use the new module to address carbon cycling and climate change across the last glacial transition. Within the constraints provided by various proxy data records, we tune the DCESS model to a Last 10 Glacial Maximum state and then conduct transient sensitivity experiments across the transition under the application of explicit transition functions for high latitude ocean exchange, atmospheric dust, and the land ice sheet extent. We compare simulated time evolutions of global mean temperature, pCO 2 , atmospheric and oceanic carbon isotopes as well as ocean dissolved oxygen concentrations with proxy data records. In this way we estimate the importance of different processes across the transition with emphasis on the role of land biosphere variations.
15Geosci. Model Dev. Discuss.,
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