Keith Lindsay - Academia.edu (original) (raw)
Papers by Keith Lindsay
Journal of Climate, 2012
To assess the climate impacts of historical and projected land cover change in the Community Clim... more To assess the climate impacts of historical and projected land cover change in the Community Climate System Model, version 4 (CCSM4), new time series of transient Community Land Model, version 4 (CLM4) plant functional type (PFT) and wood harvest parameters have been developed. The new parameters capture the dynamics of the Coupled Model Intercomparison Project phase 5 (CMIP5) land cover change and wood harvest trajectories for the historical period from 1850 to 2005 and for the four representative concentration pathway (RCP) scenarios from 2006 to 2100. Analysis of the biogeochemical impacts of land cover change in CCSM4 reveals that the model produced a historical cumulative land use flux of 127.7 PgC from 1850 to 2005, which is in general agreement with other global estimates of 156 PgC for the same period. The biogeophysical impacts of the transient land cover change parameters were cooling of the near-surface atmosphere over land by 20.18C, through increased surface albedo and reduced shortwave radiation absorption. When combined with other transient climate forcings, the higher albedo from land cover change was counteracted by decreasing snow albedo from black carbon deposition and high-latitude warming. The future CCSM4 RCP simulations showed that the CLM4 transient PFT parameters can be used to represent a wide range of land cover change scenarios. In the reforestation scenario of RCP 4.5, CCSM4 simulated a drawdown of 67.3 PgC from the atmosphere into the terrestrial ecosystem and product pools. By contrast the RCP 8.5 scenario with deforestation and high wood harvest resulted in the release of 30.3 PgC currently stored in the ecosystem.
Atmospheric Chemistry and Physics, 2010
... on the shorter in situ Barbados concentration data (1968 to 2000) (Prospero and Lamb, 2003), ... more ... on the shorter in situ Barbados concentration data (1968 to 2000) (Prospero and Lamb, 2003), and extrapolate a similar less dusty early part ... several updates relative to CLM3.5 (Oleson et al., 2008) including a land biogeochemistry model (Thorn-ton et al., 2007; Thornton et al ...
CCSM4 with ocean and land ecosystem and freely evolving atmospheric carbondioxide is used to quan... more CCSM4 with ocean and land ecosystem and freely evolving atmospheric carbondioxide is used to quantify the response of carbon fluxes and climate to changes in orbital forcing. Compared to the present-day simulation, the simulation with the Earth's orbital parameters from 115.000 years ago features significantly cooler northern high latitudes, but only moderately cooler southern high latitudes. This asymmetry is explained by the sea-ice/snow albedo feedback; the MOC is almost unchanged. Most importantly, there is a substantial build up of snow cover on Baffin Island and North Canada - the origins of the Laurentide Ice Sheet. The strong northern high-latitude cooling and the direct insolation induced tropical warming lead to global shifts in precipitation and winds of the same order. However, the differences in global net air-sea carbon fluxes are small, and provide no support for the hypothesis that the solubility pump is responsible for the intial drawdown of atmospheric CO2 duri...
Proceedings of The National Academy of Sciences, 2005
Climate change is expected to influence the capacities of the land and oceans to act as repositor... more Climate change is expected to influence the capacities of the land and oceans to act as repositories for anthropogenic CO2, and hence provide a feedback to climate change. A series of experiments with the NCAR-CSM1 coupled carbon-climate model shows that carbon sink strengths are inversely related to the rate of fossil fuel emissions, so that carbon storage capacities of the
Journal of Geophysical Research: Biogeosciences, 2014
• We analyzed emission-driven simulations from 15 Earth System Models (ESMs) • Most ESMs had a sm... more • We analyzed emission-driven simulations from 15 Earth System Models (ESMs) • Most ESMs had a small positive bias in contemporary atmospheric CO 2 predictions • We used a linear relationship to create a trajectory of future atmospheric CO 2
ABSTRACT Iron is a key nutrient for phytoplankton growth in the surface ocean. At high latitudes,... more ABSTRACT Iron is a key nutrient for phytoplankton growth in the surface ocean. At high latitudes, the iron cycle is closely related to sea ice. In recent decades, Arctic sea ice cover has been declining rapidly and Antarctic sea ice has exhibited large regional trends. A significant reduction of sea ice in both hemispheres is projected in future climate scenarios. To study impacts of sea ice on the iron cycle, iron sequestration in ice is incorporated to the Biogeochemical Elemental Cycling (BEC) model. Sea ice acts as a reservoir of iron during winter and releases iron to the surface ocean in spring and summer. Simulated iron concentrations in sea ice generally agree with observations, in regions where iron concentrations are lower. The maximum iron concentrations simulated in the Arctic sea ice and the Antarctic sea ice are 192 nM and 134 nM, respectively. These values are much lower than observed, which is likely due to missing biological processes in sea ice. The largest iron source to sea ice is suspended sediments, contributing fluxes of iron of 2.2 × 108 mol Fe month-1 to the Arctic and 4.1 × 106 mol Fe month-1 to the Southern Ocean during summer. As a result of the iron flux from ice, iron concentrations increase significantly in the Arctic. Iron released from melting ice increases phytoplankton production in spring and summer and shifts phytoplankton community composition in the Southern Ocean. Simulation results for the period of 1998 to 2007 indicate that a reduction of sea ice in the Southern Ocean will have a negative influence on phytoplankton production. Iron transport by sea ice appears to be an important process bringing iron to the central Arctic. Impacts of iron fluxes from ice to ocean on marine ecosystems are negligible in the current Arctic Ocean, as iron is not typically the growth-limiting nutrient. However, it may become a more important factor in the future, particularly in the central Arctic, as iron concentrations will decrease with declining sea ice cover and transport.
Journal of Climate, 2014
ABSTRACT Version 1 of the Community Earth System Model, in the configuration where its full carbo... more ABSTRACT Version 1 of the Community Earth System Model, in the configuration where its full carbon cycle is enabled, is introduced and documented. In this configuration, the terrestrial biogeochemical model, which includes carbon?nitrogen dynamics and is present in earlier model versions, is coupled to an ocean biogeochemical model and atmospheric CO2 tracers. The authors provide a description of the model, detail how preindustrial-control and twentieth-century experiments were initialized and forced, and examine the behavior of the carbon cycle in those experiments. They examine how sea- and land-to-air CO2 fluxes contribute to the increase of atmospheric CO2 in the twentieth century, analyze how atmospheric CO2 and its surface fluxes vary on interannual time scales, including how they respond to ENSO, and describe the seasonal cycle of atmospheric CO2 and its surface fluxes. While the model broadly reproduces observed aspects of the carbon cycle, there are several notable biases, including having too large of
Progress in Oceanography, 2011
137Cs originating from global fallout is transported into the ocean interior by advection and dif... more 137Cs originating from global fallout is transported into the ocean interior by advection and diffusion, and the 137Cs concentration is reduced by radioactive decay. 137Cs concentrations in the global ocean can be simulated by global integration of the coarse-resolution Parallel Ocean Program to understand the mechanism of material transport in the ocean. We investigated the transport mechanism of 137Cs to
Journal of Climate, 2013
Changes in atmospheric CO 2 variability during the twenty-first century may provide insight about... more Changes in atmospheric CO 2 variability during the twenty-first century may provide insight about ecosystem responses to climate change and have implications for the design of carbon monitoring programs. This paper describes changes in the three-dimensional structure of atmospheric CO 2 for several representative concentration pathways (RCPs 4.5 and 8.5) using the Community Earth System Model-Biogeochemistry (CESM1-BGC). CO 2 simulated for the historical period was first compared to surface, aircraft, and column observations. In a second step, the evolution of spatial and temporal gradients during the twenty-first century was examined. The mean annual cycle in atmospheric CO 2 was underestimated for the historical period throughout the Northern Hemisphere, suggesting that the growing season net flux in the Community Land Model (the land component of CESM) was too weak. Consistent with weak summer drawdown in Northern Hemisphere high latitudes, simulated CO 2 showed correspondingly weak north-south and vertical gradients during the summer. In the simulations of the twenty-first century, CESM predicted increases in the mean annual cycle of atmospheric CO 2 and larger horizontal gradients. Not only did the mean north-south gradient increase due to fossil fuel emissions, but east-west contrasts in CO 2 also strengthened because of changing patterns in fossil fuel emissions and terrestrial carbon exchange. In the RCP8.5 simulation, where CO 2 increased to 1150 ppm by 2100, the CESM predicted increases in interannual variability in the Northern Hemisphere midlatitudes of up to 60% relative to present variability for time series filtered with a 2-10-yr bandpass. Such an increase in variability may impact detection of changing surface fluxes from atmospheric observations.
Journal of Climate, 2012
To assess the climate impacts of historical and projected land cover change in the Community Clim... more To assess the climate impacts of historical and projected land cover change in the Community Climate System Model, version 4 (CCSM4), new time series of transient Community Land Model, version 4 (CLM4) plant functional type (PFT) and wood harvest parameters have been developed. The new parameters capture the dynamics of the Coupled Model Intercomparison Project phase 5 (CMIP5) land cover change and wood harvest trajectories for the historical period from 1850 to 2005 and for the four representative concentration pathway (RCP) scenarios from 2006 to 2100. Analysis of the biogeochemical impacts of land cover change in CCSM4 reveals that the model produced a historical cumulative land use flux of 127.7 PgC from 1850 to 2005, which is in general agreement with other global estimates of 156 PgC for the same period. The biogeophysical impacts of the transient land cover change parameters were cooling of the near-surface atmosphere over land by 20.18C, through increased surface albedo and reduced shortwave radiation absorption. When combined with other transient climate forcings, the higher albedo from land cover change was counteracted by decreasing snow albedo from black carbon deposition and high-latitude warming. The future CCSM4 RCP simulations showed that the CLM4 transient PFT parameters can be used to represent a wide range of land cover change scenarios. In the reforestation scenario of RCP 4.5, CCSM4 simulated a drawdown of 67.3 PgC from the atmosphere into the terrestrial ecosystem and product pools. By contrast the RCP 8.5 scenario with deforestation and high wood harvest resulted in the release of 30.3 PgC currently stored in the ecosystem.
Atmospheric Chemistry and Physics, 2010
... on the shorter in situ Barbados concentration data (1968 to 2000) (Prospero and Lamb, 2003), ... more ... on the shorter in situ Barbados concentration data (1968 to 2000) (Prospero and Lamb, 2003), and extrapolate a similar less dusty early part ... several updates relative to CLM3.5 (Oleson et al., 2008) including a land biogeochemistry model (Thorn-ton et al., 2007; Thornton et al ...
CCSM4 with ocean and land ecosystem and freely evolving atmospheric carbondioxide is used to quan... more CCSM4 with ocean and land ecosystem and freely evolving atmospheric carbondioxide is used to quantify the response of carbon fluxes and climate to changes in orbital forcing. Compared to the present-day simulation, the simulation with the Earth's orbital parameters from 115.000 years ago features significantly cooler northern high latitudes, but only moderately cooler southern high latitudes. This asymmetry is explained by the sea-ice/snow albedo feedback; the MOC is almost unchanged. Most importantly, there is a substantial build up of snow cover on Baffin Island and North Canada - the origins of the Laurentide Ice Sheet. The strong northern high-latitude cooling and the direct insolation induced tropical warming lead to global shifts in precipitation and winds of the same order. However, the differences in global net air-sea carbon fluxes are small, and provide no support for the hypothesis that the solubility pump is responsible for the intial drawdown of atmospheric CO2 duri...
Proceedings of The National Academy of Sciences, 2005
Climate change is expected to influence the capacities of the land and oceans to act as repositor... more Climate change is expected to influence the capacities of the land and oceans to act as repositories for anthropogenic CO2, and hence provide a feedback to climate change. A series of experiments with the NCAR-CSM1 coupled carbon-climate model shows that carbon sink strengths are inversely related to the rate of fossil fuel emissions, so that carbon storage capacities of the
Journal of Geophysical Research: Biogeosciences, 2014
• We analyzed emission-driven simulations from 15 Earth System Models (ESMs) • Most ESMs had a sm... more • We analyzed emission-driven simulations from 15 Earth System Models (ESMs) • Most ESMs had a small positive bias in contemporary atmospheric CO 2 predictions • We used a linear relationship to create a trajectory of future atmospheric CO 2
ABSTRACT Iron is a key nutrient for phytoplankton growth in the surface ocean. At high latitudes,... more ABSTRACT Iron is a key nutrient for phytoplankton growth in the surface ocean. At high latitudes, the iron cycle is closely related to sea ice. In recent decades, Arctic sea ice cover has been declining rapidly and Antarctic sea ice has exhibited large regional trends. A significant reduction of sea ice in both hemispheres is projected in future climate scenarios. To study impacts of sea ice on the iron cycle, iron sequestration in ice is incorporated to the Biogeochemical Elemental Cycling (BEC) model. Sea ice acts as a reservoir of iron during winter and releases iron to the surface ocean in spring and summer. Simulated iron concentrations in sea ice generally agree with observations, in regions where iron concentrations are lower. The maximum iron concentrations simulated in the Arctic sea ice and the Antarctic sea ice are 192 nM and 134 nM, respectively. These values are much lower than observed, which is likely due to missing biological processes in sea ice. The largest iron source to sea ice is suspended sediments, contributing fluxes of iron of 2.2 × 108 mol Fe month-1 to the Arctic and 4.1 × 106 mol Fe month-1 to the Southern Ocean during summer. As a result of the iron flux from ice, iron concentrations increase significantly in the Arctic. Iron released from melting ice increases phytoplankton production in spring and summer and shifts phytoplankton community composition in the Southern Ocean. Simulation results for the period of 1998 to 2007 indicate that a reduction of sea ice in the Southern Ocean will have a negative influence on phytoplankton production. Iron transport by sea ice appears to be an important process bringing iron to the central Arctic. Impacts of iron fluxes from ice to ocean on marine ecosystems are negligible in the current Arctic Ocean, as iron is not typically the growth-limiting nutrient. However, it may become a more important factor in the future, particularly in the central Arctic, as iron concentrations will decrease with declining sea ice cover and transport.
Journal of Climate, 2014
ABSTRACT Version 1 of the Community Earth System Model, in the configuration where its full carbo... more ABSTRACT Version 1 of the Community Earth System Model, in the configuration where its full carbon cycle is enabled, is introduced and documented. In this configuration, the terrestrial biogeochemical model, which includes carbon?nitrogen dynamics and is present in earlier model versions, is coupled to an ocean biogeochemical model and atmospheric CO2 tracers. The authors provide a description of the model, detail how preindustrial-control and twentieth-century experiments were initialized and forced, and examine the behavior of the carbon cycle in those experiments. They examine how sea- and land-to-air CO2 fluxes contribute to the increase of atmospheric CO2 in the twentieth century, analyze how atmospheric CO2 and its surface fluxes vary on interannual time scales, including how they respond to ENSO, and describe the seasonal cycle of atmospheric CO2 and its surface fluxes. While the model broadly reproduces observed aspects of the carbon cycle, there are several notable biases, including having too large of
Progress in Oceanography, 2011
137Cs originating from global fallout is transported into the ocean interior by advection and dif... more 137Cs originating from global fallout is transported into the ocean interior by advection and diffusion, and the 137Cs concentration is reduced by radioactive decay. 137Cs concentrations in the global ocean can be simulated by global integration of the coarse-resolution Parallel Ocean Program to understand the mechanism of material transport in the ocean. We investigated the transport mechanism of 137Cs to
Journal of Climate, 2013
Changes in atmospheric CO 2 variability during the twenty-first century may provide insight about... more Changes in atmospheric CO 2 variability during the twenty-first century may provide insight about ecosystem responses to climate change and have implications for the design of carbon monitoring programs. This paper describes changes in the three-dimensional structure of atmospheric CO 2 for several representative concentration pathways (RCPs 4.5 and 8.5) using the Community Earth System Model-Biogeochemistry (CESM1-BGC). CO 2 simulated for the historical period was first compared to surface, aircraft, and column observations. In a second step, the evolution of spatial and temporal gradients during the twenty-first century was examined. The mean annual cycle in atmospheric CO 2 was underestimated for the historical period throughout the Northern Hemisphere, suggesting that the growing season net flux in the Community Land Model (the land component of CESM) was too weak. Consistent with weak summer drawdown in Northern Hemisphere high latitudes, simulated CO 2 showed correspondingly weak north-south and vertical gradients during the summer. In the simulations of the twenty-first century, CESM predicted increases in the mean annual cycle of atmospheric CO 2 and larger horizontal gradients. Not only did the mean north-south gradient increase due to fossil fuel emissions, but east-west contrasts in CO 2 also strengthened because of changing patterns in fossil fuel emissions and terrestrial carbon exchange. In the RCP8.5 simulation, where CO 2 increased to 1150 ppm by 2100, the CESM predicted increases in interannual variability in the Northern Hemisphere midlatitudes of up to 60% relative to present variability for time series filtered with a 2-10-yr bandpass. Such an increase in variability may impact detection of changing surface fluxes from atmospheric observations.