Ninth International Conference on Permafrost ... - IARC Research

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Bathymetric Mapping of Lakes in the Western Arctic Coastal Plain, AlaskaBarry WinstonUniversity of Cincinnati, Cincinnati, USAKenneth HinkelDepartment of Geography, University of Cincinnati, Cincinnati, USARichard BeckDepartment of Geography, University of Cincinnati, Cincinnati, USAIntroductionThe Arctic Coastal Plain (ACP) of northern Alaskais characterized by thousands of lakes developed atopcontinuous permafrost. This region can be subdivided intothe Younger Outer Coastal Plain (YOCP), the Outer CoastalPlain (OCP), and the Inner Coastal Plain (ICP) (Hinkel etal. 2005), which are demarcated by ancient shorelines at23–29 m. a.s.l. and 7 m a.s.l. (Hopkins 1973, Péwé 1975).These subregions can be further differentiated by surficialsediments that reflect the effects of recent geomorphicprocesses, with fine-grained marine sediments associatedwith the OCP and YOCP and eolian sand characteristic ofthe ICP (O’Sullivan 1961, Williams et al. 1978, Williams1983). Lakes are significantly different among these threesubregions with respect to lake surface area, depth, and lakedensity (Hinkel et al. 2005).Many lakes on the ACP have depths of less than 2 m(Carson & Hussey 1962). Such lakes are shallow enoughthat water freezes to the lake bottom during winter and iscontinuous with the underlying permafrost. However, in thecase of deeper lakes, water at depth remains unfrozen. Withwater temperature above freezing, the underlying permafrostbegins to thaw, thereby creating a thaw bulb. The thaw bulbexpands and the substrate slowly subsides as it loses volumewhen pore ice is converted to water. As the lake growslarger and deeper over time, the thaw bulb beneath the lakeexpands, the underlying permafrost thaws, and the groundsubsides further. It is possible for the thaw bulb to reach themaximum depth of permafrost (>300 m) in large, deep lakes,resulting in the formation of an open talik (French 2007).Several models for lakes on the ACP suggest that thesefeatures develop, expand, and drain as part of a cyclicalprocess (Cabot 1947, Carson & Hussey 1962, Everett1980, Billings & Peterson 1980). However, recent researchsuggests that lake evolution is more complex and may not beapplicable across the entire ACP (Jorgenson & Shur 2007).The goal of this study is to gather basic bathymetric andsedimentological information from these small, deep lakes.They appear to be fundamentally different from the wellstudiedlakes of the OCP that were used to develop the thawlakecyclical model.Study Area and MethodologyThe lakes reported on here are all with 32 km of ourbase camp at 70°0′N and 153°5′W. They are located withinthe ICP and are characterized by deep central basins andprominent shelves composed of sand deposits. Bathymetricdata were collected along transects from 17 lakes during latesummer 2007 to determine general basin depth, slope, andmorphological characteristics.Depth measurements from the lakes were recorded with anEagle SeaCharter 502c DF iGPS sonar mounted to the sternof the vessel. The sonar was equipped with a 50/200 kHzdual-frequency transducer that was positioned approximately15 cm below the water surface. The GPS was calibratedto UTM Zone 5 North, NAD-1983 and had a locationalaccuracy better than 3 m. The data were collected by makinga series of transect passes across the lakes, recording bothdepth and location once every second. The distance betweeneach sample was estimated during post-processing of theGPS locations. The slope was calculated between each pairof samples using the depth measurements.Results and ConclusionsOut of the 17 lakes sampled, 7 lakes contained deep basinsthat exceed a depth of 10 m; the maximum recorded depth inone lake was 19 m. These 7 lakes contained shallow shelvesthat declined into deep basins over short distances. However,the deep basins were not always located in the center of thelake, and several lakes contained multiple basins or exhibiteddiscontinuous basins.The shelves were very shallow (0.3–3 m), with dunesand ripples apparent in the sandy sediment. The basin floorswere relatively flat (1–2°), and the shelf-basin transition areaaveraged 30°. However, for the 2 transects shown in Figures1 and 2, a slope of 54° was estimated in Lake A, and a slopeof 44° was determined in Lake B.The sandy lake bottom sediments should have an angleof repose no greater than 35° (Stegner & Wesfreid 1999).However, in the case of the 2 observed lakes, the slope wassignificantly greater. This suggests that the shelf sedimentsare bonded by permafrost, since unconsolidated sand cannotmaintain the observed slope.It is not known if the permafrost is syngenetic, andaggraded upward with sediment deposition along the lakemargin. The association of the deepest lake basins (~18 m)with oversteepened slopes suggests thaw bulb developmentand subsidence. However, thaw consolidation is typicallynot very effective in sandy sediments unless significantlyenriched in ice. Jorgenson & Shur (2007) indicate that nearsurfacesediment cores from this region of the ACP havenot evidenced ice oversaturation. Subsequent fieldwork onlakes in the ACP will focus on mapping lake bathymetry,347
Ni n t h In t e r n at i o n a l Co n f e r e n c e o n Pe r m a f r o s tFigure 1. Landsat-7 grayscale image showing two sampled lakes.White lines indicate data acquisition path. For reference, Lake A ison the left; Lake B is on the right.Figure 2. Associated transect profiles. Transect in Lake A is fromwest to east; transect in Lake B is from south to north.French, H.M. 2007. The Periglacial Environment, 3 rd ed.England: John Wiley and Sons Ltd.Hinkel, K.M., Frohn, R.C., Nelson, F.E., Eisner, W.R. &Beck, R.A. 2005. Morphometric and spatial analysesof thaw lakes and drained thaw lake basins in thewestern Arctic coastal plain, Alaska. Permafrost andPeriglacial Processes 16: 327-341.Hopkins, D.M. 1973. Sea level history in Beringia duringthe last 210,000 years. Quaternary Research 3: 520-540.Jorgenson, M.T. & Shur, Y. 2007. Evolution of lakes andbasins in northern Alaska and discussion of thaw lakecycle. Journal of Geophysical Research (in press).O’Sullivan, J.B. 1961. Quaternary geology of the ArcticCoastal Plain, northern Alaska. Ph.D. Dissertation.Ames: Iowa State University Science andTechnology.Péwé, T.L. 1975. Quaternary Geology of Alaska. U.S.Geological Survey Professional Paper 835.Stegner, A. & Wesfreid, J.E. 1999. Dynamical evolution ofsand ripples under water. Physical Review 60: 3487-3490.Williams, J.R. 1983. Engineering-Geologic Maps ofNorthern Alaska, Meade River Quadrangle. U.S.Geological Survey Open File Rep. 83-294.Williams, J.R., Carter, L.D. & Yeend, W.E. 1978. CoastalPlain Deposits of NPRA, In: K.A. Johnson (ed.), TheU.S. Geological Survey in Alaska: AccomplishmentsDuring 1977. Reston, VA: USGS, Circ. 77-2 B.collecting bottom cores, and conducting ground penetratingradar investigations.AcknowledgmentsThis work was supported by the NSF under grants9732051 & 0094769 to KMH and 0548846 & 0539167 toW. Eisner. Any opinions, findings, or conclusions expressedin this material are those of the authors. We appreciatesupport from the Barrow Arctic Science Consortium and theUkpeagvik Inupiat Corporation.ReferencesBillings, W.D. & Peterson, K.M. 1980. Vegetational changeand ice-wedge polygons through the thaw-lake cyclein Arctic Alaska. Arctic and Alpine Research 12: 413-432.Cabot, E.C. 1947. The northern Alaska coastal plaininterpreted from aerial photographs. GeographicalReview 37: 369-648.Carson, C.E. & Hussey, K.M. 1962. The oriented thaw lakesof northern Alaska. Journal of Geology 70: 417-439.Carter, L.D. 1981. A Pleistocene sand sea on the Alaskanarctic coastal plain. Science 211: 381-383.Everett, K.R. 1980. Landforms. Geobotanical Atlas of thePrudhoe Bay Region, Alaska. Hanover, NH: U.SArmy Cold Regions Reserve.348
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NICOP 2008 Ninth <
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ContentsPreface ...................
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Mapping and Modeling the Distributi
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Satellite Observations of Frozen Gr
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xiiIce Wedge Thermal Regime in Nort
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xivPermafrost Response to Dynamics
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xvi
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NICOP SponsorsUniversitiesUniversit
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Deep Permafrost Studies at the Lupi
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Effect of Fire on Pond Dynamics in
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Cryological Status of Russian Soils
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Acoustical Surveys of Methane Plume
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Permafrost Delineation Near Fairban
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Preparatory Work for a Permanent Ge
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A Provisional Soil Map of the Trans
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Martian Permafrost Depths from Orbi
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Time Series Analyses of Active Micr
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Impact of Permafrost Degradation on
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DC Resistivity Soundings Across a P
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Modeling Thermal and Moisture Regim
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A Provisional Permafrost Map of the
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Alpine Permafrost Distribution at M
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Cryogenic Formations of the Caucasu
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Modeling Potential Climatic Change
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A Hypothesis: A Condition of Growth
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Modeled Continual Surface Water Sto
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Freeze/Thaw Properties of Tundra So
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Discontinuous Permafrost Distributi
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Thermal Regime Within an Arctic Was
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Seasonal and Interannual Variabilit
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Twelve-Year Thaw Progression Data f
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Continued Permafrost Warming in Nor
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Landsliding Following Forest Fire o
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A Permafrost Model Incorporating Dy
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Seasonal Sources of Soil Respiratio
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Greenland Permafrost Temperature Si
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The Importance of Snow Cover Evolut
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The Account of Long-Term Air Temper
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The Combined Isotopic Analysis of L
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Adaptating and Managing Nunavik’s
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Human Experience of Cryospheric Cha
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HiRISE Observations of Fractured Mo
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A Soil Freeze-Thaw Model Through th
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Mapping and Modeling the Distributi
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First Results of Ground Surface Tem
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Historical Changes in the Seasonall
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Rock Glaciers in the Kåfjord Area,
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Snowpack Evolution on Permafrost, N
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Climate Change in Permafrost Region
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Maximizing Construction Season in a
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Pleistocene Sand-Wedge, Composite-W
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