WALE - Western Arctic Linkage Experiment
Models
In this study, we will use five models (ARCSyM, LSM, STM-TEM, ALFRESCO, PADBM) to explore linkages between the atmosphere, the land, and the ocean in the regional functioning of the Arctic System:
The ARCSyM (Lynch et al., 1995) combines representations of the atmosphere, land surface, sea ice and ocean over a limited area and can be implemented at a range of grid resolutions (generally from 10 to 100 km) and locations. The ocean component of ARCSyM includes a sigma-coordinate, free-surface primitive equation ocean model (Blumberg and Mellor, 1987) with a high-resolution mixed layer model able to resolve vertical ocean convection (Kantha and Clayson, 1994; Bailey et al., 1997). Sea ice is modeled based on the Hunke and Dukowicz (1997) elastic-viscous-plastic ice dynamics, with an ice thickness distribution following Flato and Hibler (1995), and Parkinson and Washington (1979) ice thermodynamics with modifications following Schramm et al. (1997). The performance of the ocean and sea ice components have been examined by Lynch et al. (1998), in studies of the effects of the oceanic mixed layer and ocean circulation in the Beaufort Sea (Bailey et al., 1997), studies of polyna formation in the Bering Strait (Lynch et al., 1997), and analysis of sea ice anomalies in the Arctic Ocean (Maslanik et al., 2000b).
The ARCSyM/LSM incorporates the NCAR LSM (Bonan, 1996), and can be run over a spatially explicit domain or as a single column. The NCAR LSM is a one-dimensional model of energy, momentum, and water exchange between the atmosphere and land, accounting for ecological differences among vegetation types, hydraulic and thermal differences among soil types, and allowing for a multiple of surface types including lakes and wetlands within a grid cell. The NCAR LSM is capable of making estimates of net photosynthesis, net primary production, and net ecosystem production for mature ecosystems, but does not currently simulate net carbon exchange with the atmosphere that accounts for the effects of disturbance on carbon dynamics.
The STM-TEM (Zhuang et al., 2000a, 2000b) is a new version of the Terrestrial Ecosystem Model (TEM; Tian et al., 1999; McGuire et al. 2000a, 2000b, 2000c; Clein et al. 2000a, 2000b) that couples permafrost dynamics with the biogeochemistry of high latitude ecosystems. The model simulates the major carbon and nitrogen fluxes of high latitude ecosystems, and can be applied at the same spatial resolution as ARCSyM/LSM. The STM-TEM is capable of simulating permafrost dynamics and biogeochemical responses to prescribed changes in climate, atmospheric CO2, and disturbance regimes. The TEM has been used to investigate a number of issues influencing carbon dynamics in high latitudes (see prior research section).
The Alaska Frame Based Ecosystem Code (ALFRESCO; Starfield and Chapin, 1996; Chapin and Starfield, 1997; Rupp et al., 2000a, 2000b, 2000c) simulates the timing and location of fire disturbance and the timing of vegetation transitions at decadal time steps and 2-km resolution in high latitude regions (Rupp et al., 2000a, 2000b, 2000c). ALFRESCO has been coupled to TEM to simulate the role of fire disturbance and vegetation dynamics in the response of carbon dynamics to transient scenarios of projected climate change for the Seward Peninsula of Alaska (Rupp and McGuire, unpublished). This research has revealed that the large-scale application of ALFRESCO as part of a coupled functional-structural model of ecosystem dynamics is best accomplished by modifying ALFRESCO so that it operates at a spatial resolution appropriate to a regional climate model and at annual time steps.
The modeling component of PADBM includes the Permafrost Water Balance Model (P/WBM) (Holden 1999, Lammers et al., 2000b) which represents enhancements over the existing non-Arctic version of the global WBM (Vorosmarty et al. 1989). These enhancements include improved handling of the snowpack and inclusion of degree-day thaw depth and permafrost extent calculations. The model produces estimates of time-varying water budgets over heterogeneous Arctic watersheds and links computed runoff to a Water Transport Model (Vorosmarty et al. 1996, Fekete et al., 2000b), which transports continental runoff through simulated river networks to the oceans.