Lori Thompson Sentman

Research Interests

Developing and using comprehensive climate and biosphere models of the atmosphere-ocean-ice-land system to identify and elucidate physical, biogeochemical and ecological mechanisms, asses and understand the predictability of the Earth system on seasonal and longer time scales, and evaluate the impact of anthropogenic activity on the Earth system.

Research Activities

• interactions and feedbacks of climate on the terrestrial biosphere carbon cycle
• impact of land use change on the terrestrial biosphere carbon stores and fluxes
• sensitivity of the terrestrial biosphere carbon cycle to atmospheric initial conditions
• Model execution, analysis and management of Earth System Model (ESM) Coupled Model Intercomparison Project Phase 5 (CMIP5) and Intergovernmental Panel on Climate Change 5th Assessment Report (IPCC AR5) simulations.
  

Key Publications

Shevliakova, Elena, S. W. Pacala, Sergey Malyshev, G. C. Hurtt, P.C.D. Milly, J. P. Caspersen, Lori T. Sentman, J. P. Fisk, C. Wirth, and C. Crevoisier, 2009, Carbon Cycling under 300 Years of Land-use Change: the Importance of the Secondary Vegetation Sink. Global Biogeochemical Cycles, 23, GB2022, doi:10.1029/2007GB003176. [ Abstract PDF].

We have developed a dynamic land model (LM3V) able to simulate ecosystem dynamics and exchanges of water, energy and CO2 between land and atmosphere. LM3V is specifically designed to address the consequences of land-use/land-management changes including cropland and pasture dynamics, shifting cultivation, logging, fire, and resulting patterns of secondary regrowth. Here we analyze the behavior of LM3V, forced with the output from the Geophysical Fluid Dynamics Laboratory (GFDL) atmospheric model AM2, observed precipitation data and four historic scenarios of land-use change for 1700-2000. Our analysis suggests a net terrestrial carbon source due to land-use activities from 1.1 to 1.3 GtC/yr during the 1990s, where the range is due to the difference in the historic cropland distribution. This magnitude is substantially smaller than previous estimates from other models, largely due to our estimates of a secondary vegetation sink of 0.35 to 0.6 GtC/yr in the 1990s and decelerating agricultural land clearing since the1960s. For the 1990s, our estimates for the pastures carbon flux vary from a source of 0.37 to a sink of 0.15 GtC/yr, and for the croplands our model shows a carbon source of 0.6 to 0.9 GtC/yr. Our process-based model suggests a smaller net deforestation source than earlier bookkeeping models because it accounts for decelerated net conversion of primary forest to agriculture and for stronger secondary vegetation regrowth in tropical regions. The overall uncertainty is likely to be higher than the range reported here because of uncertainty in the biomass recovery under changing ambient conditions, including atmospheric CO2 concentration, nutrients availability and climate.

Appears in Nature Reports Climate Change | Vol 5 | April 2009.

Sentman, Lori T., Elena Shevliakova, Ronald J. Stouffer, Sergey Malyshev, 2009: Evaluating the time scale of the terrestrial carbon response to land use and implications for initializing an Earth System Model. In prep.

Shevliakova, Elena, Ronald J. Stouffer, Lori T. Sentman, S. W. Pacala, Michael J. Spelman, Sergey Malyshev, 2009: Uncertainty in the land-carbon uptake due to CO₂ fertilization under climate change. In prep.