Debolskiy and three co-authors reported mid-2020 that Permafrost, a key component of Arctic ecosystems, is currently affected by climate warming and anticipated to undergo further significant changes in this century. The most pronounced changes are expected to occur in the transition zone between the discontinuous and continuous types of permafrost. The authors applied a transient temperature dynamic model to investigate the spatiotemporal evolution of permafrost conditions on the Seward Peninsula, Alaska—a region currently characterized by continuous permafrost in its northern part and discontinuous permafrost in the south.
They calibrated model parameters using a variational data assimilation technique exploiting historical ground temperature measurements collected across the study area. The model is then evaluated with a separate control set of the ground temperature data. Calibrated model parameters are distributed across the domain according to ecosystem types. The forcing applied to their model consists of historic monthly temperature and precipitation data and climate
projections based on the Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios.
Simulated near‐surface permafrost extent for the 2000–2010 decade agrees well with existing permafrost maps and previous Alaska‐wide modeling studies. Future projections suggest a significant increase (3.0°C under RCP 4.5 and 4.4°C under RCP 8.5 at the 2 m depth) in mean decadal ground temperature on average for the peninsula for the 2090–2100 decade when compared to the period of 2000–2010. Widespread degradation of the near‐surface permafrost is projected to reduce its extent at the end of the 21st century to only 43% of the peninsula's area under RCP 4.5 and 8% under RCP 8.5.
The authors concluded that in this study they expanded the high‐resolution ground temperature products developed earlier for the North Slope of Alaska (Nicolsky et al., 2017) to the Seward Peninsula. In addition, they added a model parameter to the snowpack submodule to account for different effects of vegetation on snow accumulation and redistribution and enhanced an existing data assimilation approach for a better model calibration, which is later
verified by the model evaluation.
Modeling results for the present‐day permafrost extent and temperature are generally in agreement with previous studies (Jafarov et al., 2012; Jorgenson et al., 2008; Marchenko et al., 2008) given the difference in the approaches, spatial scales, and climate data utilized. Substantial changes in permafrost are projected for the end of the 21st century.
The whole peninsula experiences a steady increase in air temperatures under both RCP 4.5 and 8.5. For RCP 4.5 in the last decade of the 21st century in more than a half of the Seward Peninsula, the permafrost table will be disconnected from the seasonally freezing layer above it or permafrost will not be present at all. However, the areas occupied by more resilient ecotypes in the northern half of the peninsula will preserve near‐surface permafrost under a seasonally thawed layer. Under a more extreme scenario RCP 8.5, in the last decade of the 21st century, less than 10% of the peninsula will have near‐surface permafrost present.
The applicability of the modeling approach implemented in this study to other regions and different spatial resolutions depends on the availability of the high‐resolution climate data, ground temperature observations available for calibration and evaluation of the model, and high‐resolution ecotype classification maps. When ground temperature observations do not cover a sufficient number of ecotypes to adequately represent the variability of surface and subsurface conditions on a target resolution, two possibilities can be considered.
Approximation of the model parameters for ecotypes where calibration data are absent by model parameters for the equivalent ecotype from an adjacent territory for which a calibration was already done should be considered. If no equivalent ecotype can be found, planning and implementing a ground temperature data acquisition campaign should fill the necessary gaps.
Managed & Built by I2M Consulting, LLC | © 2010-
