I. Totterdell | The Met Office (original) (raw)
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University of the Basque Country, Euskal Herriko Unibertsitatea
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Papers by I. Totterdell
IOP Conference Series: Earth and Environmental Science, 2009
This article was submitted without an abstract, please refer to the full-text PDF file.
Biogeosciences Discussions, 2008
The first step in developing an operational model of ocean biogeochemistry is presented. The Cent... more The first step in developing an operational model of ocean biogeochemistry is presented. The Centre for observation of Air-Sea Interactions and fluXes (CASIX), funded by the UK Natural Environment Research Council, aims to quantify the air-sea fluxes of CO2 accurately and on a global scale. An important tool for achieving this aim will be a model of the ocean carbon cycle which can accurately represent the short time-scale variability of CO2 fluxes. It is intended that such a model will be able to assimilate physical and biogeochemical data. As an initial step, the Hadley Centre Ocean Carbon Cycle (HadOCC) model has been embedded in the Met Office Forecasting Ocean Assimilation Model (FOAM). The HadOCC model features a simple Nutrient-Phytoplankton-Zooplankton-Detritus ecosystem and a representation of the carbon chemistry. The FOAM system is a suite of nested ocean models which can assimilate various types of physical data to produce a best estimate of the present physical ocean st...
Biogeosciences, 2009
We compare modeled oceanic carbon uptake in response to pulse CO 2 emissions using a suite of glo... more We compare modeled oceanic carbon uptake in response to pulse CO 2 emissions using a suite of global ocean models and Earth system models. In response to a CO 2 pulse emission of 590 Pg C (corresponding to an instantaneous doubling of atmospheric CO 2 from 278 to 556 ppm), the fraction of CO 2 emitted that is absorbed by the ocean is: 37±8%, 56±10%, and 81±4% (model mean ±2σ ) in year 30, 100, and 1000 after the emission pulse, respectively. Modeled oceanic uptake of pulse CO 2 on timescales from decades to about a century is strongly correlated with simulated presentday uptake of chlorofluorocarbons (CFCs) and CO 2 across all models, while the amount of pulse CO 2 absorbed by the ocean from a century to a millennium is strongly correlated with modeled radiocarbon in the deep Southern and Pacific Ocean. However, restricting the analysis to models that are capable of reproducing observations within uncertainty, the correlation is generally much weaker. The rates of surface-Correspondence to: L. Cao (longcao@stanford.edu) to-deep ocean transport are determined for individual models from the instantaneous doubling CO 2 simulations, and they are used to calculate oceanic CO 2 uptake in response to pulse CO 2 emissions of different sizes pulses of 1000 and 5000 Pg C. These results are compared with simulated oceanic uptake of CO 2 by a number of models simulations with the coupling of climate-ocean carbon cycle and without it. This comparison demonstrates that the impact of different ocean transport rates across models on oceanic uptake of anthropogenic CO 2 is of similar magnitude as that of climate-carbon cycle feedbacks in a single model, emphasizing the important role of ocean transport in the uptake of anthropogenic CO 2 .
Journal of Climate, 2014
Carbon cycle feedbacks are usually categorized into carbon-concentration and carbon-climate feedb... more Carbon cycle feedbacks are usually categorized into carbon-concentration and carbon-climate feedbacks, which arise owing to increasing atmospheric CO 2 concentration and changing physical climate. Both feedbacks are often assumed to operate independently: that is, the total feedback can be expressed as the sum of two independent carbon fluxes that are functions of atmospheric CO 2 and climate change, respectively. For phase 5 of the Coupled Model Intercomparison Project (CMIP5), radiatively and biogeochemically coupled simulations have been undertaken to better understand carbon cycle feedback processes. Results show that the sum of total ocean carbon uptake in the radiatively and biogeochemically coupled experiments is consistently larger by 19-58 petagrams of carbon (Pg C) than the uptake found in the fully coupled model runs. This nonlinearity is small compared to the total ocean carbon uptake (533-676 Pg C), but it is of the same order as the carbon-climate feedback. The weakening of ocean circulation and mixing with climate change makes the largest contribution to the nonlinear carbon cycle response since carbon transport to depth is suppressed in the fully relative to the biogeochemically coupled simulations, while the radiatively coupled experiment mainly measures the loss of near-surface carbon owing to warming of the ocean. Sea ice retreat and seawater carbon chemistry contribute less to the simulated nonlinearity. The authors' results indicate that estimates of the ocean carbon-climate feedback derived from ''warming only'' (radiatively coupled) simulations may underestimate the reduction of ocean carbon uptake in a warm climate high CO 2 world.
IOP Conference Series: Earth and Environmental Science, 2009
This article was submitted without an abstract, please refer to the full-text PDF file.
Biogeosciences Discussions, 2008
The first step in developing an operational model of ocean biogeochemistry is presented. The Cent... more The first step in developing an operational model of ocean biogeochemistry is presented. The Centre for observation of Air-Sea Interactions and fluXes (CASIX), funded by the UK Natural Environment Research Council, aims to quantify the air-sea fluxes of CO2 accurately and on a global scale. An important tool for achieving this aim will be a model of the ocean carbon cycle which can accurately represent the short time-scale variability of CO2 fluxes. It is intended that such a model will be able to assimilate physical and biogeochemical data. As an initial step, the Hadley Centre Ocean Carbon Cycle (HadOCC) model has been embedded in the Met Office Forecasting Ocean Assimilation Model (FOAM). The HadOCC model features a simple Nutrient-Phytoplankton-Zooplankton-Detritus ecosystem and a representation of the carbon chemistry. The FOAM system is a suite of nested ocean models which can assimilate various types of physical data to produce a best estimate of the present physical ocean st...
Biogeosciences, 2009
We compare modeled oceanic carbon uptake in response to pulse CO 2 emissions using a suite of glo... more We compare modeled oceanic carbon uptake in response to pulse CO 2 emissions using a suite of global ocean models and Earth system models. In response to a CO 2 pulse emission of 590 Pg C (corresponding to an instantaneous doubling of atmospheric CO 2 from 278 to 556 ppm), the fraction of CO 2 emitted that is absorbed by the ocean is: 37±8%, 56±10%, and 81±4% (model mean ±2σ ) in year 30, 100, and 1000 after the emission pulse, respectively. Modeled oceanic uptake of pulse CO 2 on timescales from decades to about a century is strongly correlated with simulated presentday uptake of chlorofluorocarbons (CFCs) and CO 2 across all models, while the amount of pulse CO 2 absorbed by the ocean from a century to a millennium is strongly correlated with modeled radiocarbon in the deep Southern and Pacific Ocean. However, restricting the analysis to models that are capable of reproducing observations within uncertainty, the correlation is generally much weaker. The rates of surface-Correspondence to: L. Cao (longcao@stanford.edu) to-deep ocean transport are determined for individual models from the instantaneous doubling CO 2 simulations, and they are used to calculate oceanic CO 2 uptake in response to pulse CO 2 emissions of different sizes pulses of 1000 and 5000 Pg C. These results are compared with simulated oceanic uptake of CO 2 by a number of models simulations with the coupling of climate-ocean carbon cycle and without it. This comparison demonstrates that the impact of different ocean transport rates across models on oceanic uptake of anthropogenic CO 2 is of similar magnitude as that of climate-carbon cycle feedbacks in a single model, emphasizing the important role of ocean transport in the uptake of anthropogenic CO 2 .
Journal of Climate, 2014
Carbon cycle feedbacks are usually categorized into carbon-concentration and carbon-climate feedb... more Carbon cycle feedbacks are usually categorized into carbon-concentration and carbon-climate feedbacks, which arise owing to increasing atmospheric CO 2 concentration and changing physical climate. Both feedbacks are often assumed to operate independently: that is, the total feedback can be expressed as the sum of two independent carbon fluxes that are functions of atmospheric CO 2 and climate change, respectively. For phase 5 of the Coupled Model Intercomparison Project (CMIP5), radiatively and biogeochemically coupled simulations have been undertaken to better understand carbon cycle feedback processes. Results show that the sum of total ocean carbon uptake in the radiatively and biogeochemically coupled experiments is consistently larger by 19-58 petagrams of carbon (Pg C) than the uptake found in the fully coupled model runs. This nonlinearity is small compared to the total ocean carbon uptake (533-676 Pg C), but it is of the same order as the carbon-climate feedback. The weakening of ocean circulation and mixing with climate change makes the largest contribution to the nonlinear carbon cycle response since carbon transport to depth is suppressed in the fully relative to the biogeochemically coupled simulations, while the radiatively coupled experiment mainly measures the loss of near-surface carbon owing to warming of the ocean. Sea ice retreat and seawater carbon chemistry contribute less to the simulated nonlinearity. The authors' results indicate that estimates of the ocean carbon-climate feedback derived from ''warming only'' (radiatively coupled) simulations may underestimate the reduction of ocean carbon uptake in a warm climate high CO 2 world.