Earth`s Cryosphere, 2019, Vol. XXIII, № 4, p. 22-30
IMPACTS OF CLIMATE CHANGE ON LONG-TERM DYNAMICS OF SEASONAL FREEZING IN MOSCOW REGION: RETROSPECTIVE ANALYSIS AND UNCERTAINTIES IN FORECASTING FOR THE SECOND HALF OF THE 21ST CENTURY
S.P. Pozdnyakov, S.O. Grinevskyi, E.A. Dediulina
Lomonosov Moscow State University, Faculty of Geology, Department of Hydrogeology,
1, Leninskie Gory, Moscow, 119991, Russia; sppozd@mail.ru
A quantitative analysis of the forecast dynamics of seasonal freezing depth in the 21st century has been carried out using climate projections obtained by 5 models of the Atmosphere-Ocean General Circulation Model from the CMIP5 model ensemble. This analysis is based on the simulation of snow cover dynamics on the surface and vertical heat transfer and unsaturated water flow in the topsoil and the underlying unsaturated zone. The thermophysical and hydrophysical input parameters were obtained from the inversing of the temperature data at observation sites on the territory of the Moscow State University Zvenigorod Biological Station. The epignosic simulations of freezing depth during the period of 1945–2015 have shown a decreasing trend for a period starting from 1940s through the early 1990s, with its subsequent stabilization in the late 20th and early 21st century. Predictions of seasonal freezing depth for the second half of the 21st century involved generation of three stationary meteorological time series of diurnal resolution (each spanning 100 years for the periods of 2020–2040, 2040–2060 and 2060–2080) for all of the circulation models utilizing the RCP8.5 greenhouse gas emission scenario. These series were used as boundary conditions in modeling of intra-annual dynamics of the snow cover depth at earth’s surface, and heat and moisture transfer dynamics in the underlying subsurface zone. The simulation results analysis revealed reduction of the thickness of the seasonally frozen layer and reduction by at least a month (by the 2060s and 2080s of the 21st century) of soil freezing duration due to earlier onset of steady air temperatures above zero degrees Celsius in the spring. Given those results of the heat transfer and water flow simulations for five different climate projections still differ significantly one from other, they do not allow to provide any reliable predictions of the long-term dynamics of seasonal freezing depth in the second half of the 21st century.
Depth of freezing, modeling, heat transfer and water flow, unsaturated zone, seasonally frozen layer, climate change, the thermal regime of soil