Geology, Published Online on 24 May 2011 As Doi:10.1130/G31902.1
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Geology, published online on 24 May 2011 as doi:10.1130/G31902.1 Geology Whole-edifice ice volume change A.D. 1970 to 2007/2008 at Mount Rainier, Washington, based on LiDAR surveying T.W. Sisson, J.E. Robinson and D.D. Swinney Geology published online 24 May 2011; doi: 10.1130/G31902.1 Email alerting services click www.gsapubs.org/cgi/alerts to receive free e-mail alerts when new articles cite this article Subscribe click www.gsapubs.org/subscriptions/ to subscribe to Geology Permission request click http://www.geosociety.org/pubs/copyrt.htm#gsa to contact GSA Copyright not claimed on content prepared wholly by U.S. government employees within scope of their employment. Individual scientists are hereby granted permission, without fees or further requests to GSA, to use a single figure, a single table, and/or a brief paragraph of text in subsequent works and to make unlimited copies of items in GSA's journals for noncommercial use in classrooms to further education and science. 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Citations to Advance online articles must include the digital object identifier (DOIs) and date of initial publication. © Geological Society of America Geology, published online on 24 May 2011 as doi:10.1130/G31902.1 Whole-edifi ce ice volume change A.D. 1970 to 2007/2008 at Mount Rainier, Washington, based on LiDAR surveying T.W. Sisson1*, J.E. Robinson1*, and D.D. Swinney2* 1U.S. Geological Survey, 345 Middlefi eld Road, Menlo Park, California 94025, USA 2National Park Service, Mount Rainier National Park, Ashford, Washington 98304, USA ABSTRACT Slowed retreat and local readvance of Pacifi c Net changes in thickness and volume of glacial ice and perennial snow at Mount Rainier, Northwest glaciers were coincident with a cool Washington State, have been mapped over the entire edifi ce by differencing between a high- phase of the Pacifi c Decadal Oscillation from resolution LiDAR (light detection and ranging) topographic survey of September–October ca. 1945 to ca. 1975 (Harper, 1993; Nylen, 2007/2008 and the 10 m lateral resolution U.S. Geological Survey digital elevation model 2004; Josberger et al., 2007), with above aver- derived from September 1970 aerial photography. Excepting the large Emmons and Win- age winter precipitation and below average win- throp Glaciers, all of Mount Rainier’s glaciers thinned and retreated in their terminal regions, ter sea surface temperatures along the Pacifi c with substantial thinning mainly at elevations <2000 m and the greatest thinning on south- Northwest coast (Mantua and Hare, 2002). facing glaciers. Mount Rainier’s glaciers and snowfi elds also lost volume over the interval, excepting the east-fl ank Fryingpan and Emmons Glaciers and minor near-summit snowfi elds; METHODS maximum volume losses were centered from ~1750 m (north fl ank) to ~2250 m (south fl ank) Severe rainfall in November 2006 led to elevation. The greatest single volume loss was from the Carbon Glacier, despite its northward widespread fl ooding across southwest Wash- aspect, due to its sizeable area at <2000 m elevation. Overall, Mount Rainier lost ~14 vol% ington that extensively damaged infrastruc- glacial ice and perennial snow over the 37 to 38 yr interval between surveys. Enhanced thin- ture in Mount Rainier National Park. To aid in ning of south-fl ank glaciers may be meltback from the high snowfall period of the mid-1940s recovery and long-term planning, the National to mid-1970s associated with the cool phase of the Pacifi c Decadal Oscillation. Park Service contracted for an aerial LiDAR topographic survey of Mount Rainier National INTRODUCTION Survey digital elevation model (DEM) derived Park (954 km2). An area ~100 km2 centered on Glaciers grow or shrink appreciably due to from September 1970 aerial photography. Dif- Mount Rainier’s summit was surveyed in Sep- decadal variations in ablation season tempera- ferencing these DEMs maps changes in ice tember 2007, but inclement weather halted the ture and accumulation season snowfall, and so surface elevation over a 37 to 38 yr period, and effort, and the survey was completed in Septem- can serve as visually compelling sentinels of cli- thereby the changes in ice and snow thickness ber–October 2008. Results averaged 5.73 laser mate change. Alpine glaciers advanced multiple and volume, including all of Mount Rainier’s points/m2 over the main edifi ce and forested times during the Holocene, most recently during glaciers and perennial snowfi elds. regions, with a vertical accuracy of 3.7 cm based the Little Ice Age; the last major glacial advance on 2243 real-time kinematic control points on was in the mid-1800s (Grove, 2004; Matthews GLACIERS OF MOUNT RAINIER AND open fl at road surfaces. Mean relative vertical and Briffa, 2005). Portable cameras and glass THE PACIFIC NORTHWEST accuracy is 11 cm as evaluated by comparisons plate negatives were invented at about that time, Mount Rainier sustains the greatest concen- of points on overlapping fl ightlines. Limits of leading to the earliest photographs of alpine gla- tration of glacial ice in the conterminous United ice and perennial snow were mapped utilizing ciers having been taken when they were close to States (~92 km2, or ~16% of the total ice area both shaded relief and slope images of the bare- their greatest sizes of the last few thousand years. exclusive of Alaska) including the largest gla- earth LiDAR DEM (Robinson et al., 2010). Subsequently, alpine glaciers have generally cier, the longest glacier, and the lowest terminus Changes in ice area, elevation, and volume retreated 102–103 m, though at varying rates, and, elevation (Driedger and Kennard, 1986; Krim- are referenced against the U.S. Geological Sur- in some cases, interrupted by small re advances. mel, 2002; Fountain et al., 2007). Mount Rain- vey 1/3 arc-s (~10 m lateral spacing) DEM from While the overall retreat of glaciers since the Lit- ier’s glaciers were fi rst written about in A.D. the national elevation data set (http://ned.usgs. tle Ice Age is indisputable, measures are largely 1833, and were fi rst mapped in their entirety in gov/). For the Mount Rainier area this DEM is restricted to length or area (Orelemans, 2005), 1896 (Tolmie, 1833–1865; Russell, 1898). Due derived from 1:24000 topographic maps pro- whereas direct measures of changing ice volume to their impressive size and ready accessibility, duced by photogrammetry of September 1970 and mass are few (Huss et al., 2010). Mount Rainier’s glaciers became a focus for aerial photographs. Perimeters of glaciers and Heightened interest in the scope, rates, causes, glaciological studies (Heliker et al., 1984). perennial snowfi elds in 1970 were digitized and potential consequences of climate change Mount Rainier’s glaciers were close to their from the topographic sheets using georegistered motivate improved measurements of its direct maximum Holocene sizes ca. 1850 (Sigafoos scans of the hydrologic separates (Robinson et and derivative aspects, including quantities of and Hendricks, 1972). They then retreated for a al., 2010). Most glacial terminii do not have ice and perennial snow and their rates of loss or century until the mid-1940s or early 1950s, when simple shapes, so representative terminus retreat gain. Here we assess changes in ice volume over retreat slowed, and many readvanced modestly or advance ranges from 1970 to 2007/2008 are the entire edifi ce of Mount Rainier, Washington through the early 1970s to middle 1980s; sub- reported with no distinction between active and State (United States), by differencing surface sequently, most have been in retreat (Driedger, stagnant ice (Table 1). elevations between a high-resolution light detec- 1986; Nylen, 2004). Other Pacifi c Northwest Suitability of the LiDAR and 1970 DEMs for tion and ranging (LiDAR) topographic survey glaciers behaved similarly, including on Mounts comparison was assessed from their apparent performed in September–October 2007/2008, Baker, Hood, and Adams (Harper, 1993; Jack- elevation differences exclusive of glacierized ter- and the 10 m lateral resolution U.S. Geological son and Fountain, 2007; Sitts et al., 2010), the rain, after coarsening both DEMs to coincident Blue Glacier in the Olympic Mountains (Spicer, 100 m2 pixels using a cubic-spline algorithm. *E-mails: [email protected]; [email protected]; 1989), and with less continuous readvance, the Over the entire park, the coarsened LiDAR [email protected]. South Cascade Glacier (Josberger et al., 2007). DEM averages 2.54 m low, exclusive of snow © 2011 Geological Society of America. For permission to copy, contact Copyright Permissions, GSA, or [email protected]. GEOLOGY,Geology, July July 2011; 2011 v. 39; no. 7; p. 639–642; doi:10.1130/G31902.1; 2 fi gures; 1 table; Data Repository item 2011257. 639 Geology, published online on 24 May 2011 as doi:10.1130/G31902.1 TABLE 1. GLACIER SIZE CHANGES FROM 1970 to 2007/2008, MOUNT RAINIER is also recorded by the most southerly facing Name 1970 area 2007/2008 area Mean Volume Terminus glaciers (Nisqually, Wilson, and Paradise) hav- (sector) (106 m2) (106 m2) elevation change change ing the greatest areally averaged reductions in change (106 m3) (m) surface elevation (Table 1).