Ninth International Conference on Permafrost ... - IARC Research

Permafrost Characteristics of AlaskaTorre Jorgenson, Kenji Yoshikawa, Mikhail Kanevskiy, Yuri ShurUniversity of Alaska Fairbanks, Institute of Northern Engineering, Fairbanks, Alaska, USAVladimir Romanovsky, Sergei Marchenko, Guido GrosseUniversity of Alaska Fairbanks, Geophysical Institute, Fairbanks, Alaska, USAJerry Brown<strong>International</strong> Permafrost Association, Woods Hole, Massachusetts, USABen JonesU.S. Geological Survey, Anchorage, Alaska, USAA new permafrost map of Alaska (see inside of frontcover), using a terrain-unit approach for mapping permafrostdistribution based on climate and surficial geology, ispresented. This map represents the third iteration of apermafrost map for Alaska, following the circum-Arcticpermafrost map (Brown et al. 1997), which made minormodifications to the initial map by Ferrians (1965). Tomap permafrost, we developed a rule-based model thatincorporated mean annual air temperatures (MAAT) fromthe PRISM climate map and the surficial geology map ofKarlstrom et al. (1964) modified with some new informationon geology. We used terrain-permafrost relationshipsdeveloped by Kreig and Reger (1982) and our knowledge ofpermafrost distribution to assign permafrost characteristicsto each surficial deposit under varying temperatures.We coded the map with surficial geology, MAAT, primarysoil texture, permafrost extent, ground ice volume, andprimary thermokarst landforms. The map focuses on thetop 10 m of permafrost, where permafrost can be morereadily mapped from surface features, determined by simplefield measurements, and where ground ice usually is mostabundant. Although we used recent MAAT in our model,we note that permafrost distribution is greatly affected bypast climates. We relied on many sources for the effort, butare not able to cite all references in this abstract. The mainmap shows permafrost thickness values based on Ferrians(1965), Péwé (1975), Osterkamp and Payne (1981), Collettet al. (1989), and others.The following characteristics are shown on small thematicmaps on the inside of back cover:Ground temperatures (usually measured at depths 20 to30 m) were obtained from boreholes by V. Romanovsky, G.Clow, K. Yoshikawa, D. Kane, and T. Osterkamp as part ofthe Thermal State of Permafrost project for the <strong>International</strong>Polar Year (Brown & Romanovsky 2008). Ground icevolumes were estimated for the upper 5 m of permafrostusing terrain relationship from Kreig and Reger (1982) andour field data. Ground ice volume near the surface is higherin colder regions due to active ice wedge formation andice segregation in fine-grained deposits. Pingo distributionwas compiled mostly from the literature and by satelliteimage interpretation. There are >1500 known pingos inAlaska. In central Alaska and bordering Yukon areas, thereare ~760 pingos, mostly open-system. Closed-systempingos predominate in the North Slope, Seward Peninsula,and Noatak regions. The distribution of ice wedges wasdetermined from the literature, from polygonal patternsevident on remote sensing imagery, and from our fieldexperience. Ice wedges actively form in the continuouspermafrost zone and are mostly inactive in the discontinuouszone (Péwé 1975). Holocene ice wedges are limited tothe top 3 to 5 m of permafrost; large, deep (up to 35 m)syngenetic ice wedges formed during the Late Pleistocene.Thermokarst landforms are abundant in all recent and pastpermafrost zones (Jorgenson et al. 2008). They are varied,due to differences in temperature, ground ice volume, soiltexture, slope, and hydrologic conditions.The permafrost zones underlie 80% of Alaska, includingcontinuous (29%), discontinuous (35%), sporadic (8%), andisolated (8%) permafrost. Permafrost is absent beneath 15%of the State, with glaciers and ice sheets occupying 4% andlarge water bodies, 1% of the area.ReferencesBrown, J.B., Ferrians, O.J., Heginbottom, J.A. & Melnikov,E.S. 1997. Circum-Arctic Map of Permafrost andGround-Ice Conditions. U.S. Geol. Surv. Map CP-45,scale 1:10,000,000.Brown, J. & Romanovsky, V.E. 2008. Report from the<strong>International</strong> Permafrost Association: State ofpermafrost in the first decade of the 21st century.Permafrost and Periglacial Processes 19: 255-260.Collett, T.S., Bird, K.J., Kvenvolden, K.A. & Magoon, L.B.1989. Map Showing the Depth to the Base of theDeepest Ice-Bearing Permafrost as Determined fromWell Logs, North Slope, Alaska. U.S. Geol. Surv. OilGas Inv. Map OM-222, scale 1: 1,000,000.Ferrians, O.J. 1965. Permafrost Map of Alaska. U.S. Geol.Surv. Misc. Geol. Inv. Map I-445, scale 1: 2,500,000.Jorgenson, M.T., Shur, Y. & Osterkamp, T.E. 2008.Thermokarst in Alaska. Proceedings of the <strong>Ninth</strong><strong>International</strong> <strong>Conference</strong> on Permafrost, Fairbanks,Alaska, June 29–July 3, 2008..Karlstrom, T.N.V. et al. 1964. Surficial Geology of Alaska.U.S. Geol. Surv. Misc. Geol. Inv. Map I-357, scale1:1,584,000.121