Ninth International Conference on Permafrost ... - IARC Research

Employing a Coupled Permafrost Water Balance Modelto Study Possible Changes in PermafrostD.J. NicolskyGeophysical Institute, University of Alaska Fairbanks PO Box 757320, Fairbanks, AK 99775, USAV.E. RomanovskyGeophysical Institute, University of Alaska Fairbanks PO Box 757320, Fairbanks, AK 99775, USAM.A. RawlinsJet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USAIntroductionThawing and freezing of arctic soils is affected by manyfactors, with air temperature, vegetation, snow accumulation,and soil moisture among the most significant. Here wedescribe the coupling of a Permafrost Model (Sazonova& Romanovsky 2003, Nicolsky et al. 2007) and the pan-Arctic Water Balance Model (PWBM, Rawlins et al. 2003),developed at the University of Alaska Fairbanks and theUniversity of New Hampshire, respectively. Additionally,we present resultant simulated soil temperature and moisturedynamics, depth of seasonal freezing and thawing, river runoff,and water storage across the pan-Arctic. The coupledmodels simulate the snow/ground temperature with a 5-layersnow and 23-layer soil model. In the soil model, the layersthicken with depth and span a 60 m thick column. ThePWBM has two soil storage zones: a root zone that gainswater from infiltration and loses water via evapotranspirationand horizontal and vertical drainage, and a deep zone thatgains water via root zone vertical drainage and loses watervia horizontal drainage. Forcing data (i.e., air temperature,precipitation) are taken from ERA40 datasets and fromseveral of the IPCC 4th Assessment model simulations offuture arctic climate. We validate our model simulationsby comparing soil moisture and thermal profiles withobservational data collected within the pan-Arctic.ARC-0520578, ARC-0612533, IARC-NSF CA: Project 3.1Permafrost Research), by NASA Water and Energy Cyclegrant, and by the State of Alaska.ReferencesNicolsky, D.J., Romanovsky, V.E., Alexeev, V.A. &Lawrence, D.M. 2007. Improved modeling ofpermafrost dynamics in a GCM land-surface scheme.Geophysical Research Letters 34: L08501.Rawlins, M.A., Lammers, R.B., Frolking, S., Fekete, B.M.& Vo¨ro¨smarty, C.J. 2003. Simulating pan-Arcticrunoff with a macro-scale terrestrial water balancemodel. Hydrological Processes 17: 2521-2539.Sazonova, T.S. & Romanovsky, V.E. 2003. A Model forRegional-Scale Estimation of Temporal and SpatialVariability of the Active Layer Thickness and MeanAnnual Ground Temperatures. Permafrost andPeriglacial Processes 14(2): 125-139.Coupling of Two ModelsThe coupling captures thresholds and non-linear feedbackprocesses induced by changes in hydrology and subsurfacetemperature dynamics, and hence helps us to study thespatial and temporal variability of permafrost dynamics aswell as potential future alterations to permafrost and theterrestrial arctic water cycle. Through explicit couplingof the Permafrost Model with the PWBM, we are able tosimulate the temporal and spatial variability in soil water/ice content, active layer thickness, and associated largescalehydrology that are driven by contemporary and futureclimate variability and change. Choosing appropriate climateforcings is clearly a significant challenge.AcknowledgmentsThis research was funded by ARCSS Program and by thePolar Earth Science Program, Office of Polar Programs,National Science Foundation (OPP-0120736, ARC-0632400,223