Item talk:Q226891

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 "url": "https://www.usgs.gov/programs/climate-research-and-development-program/science/gulkana-glacier",
 "headline": "Gulkana Glacier",
 "datePublished": "February 23, 2024",
 "author": [
   {
     "@type": "Person",
     "name": "Louis Sass, III",
     "url": "https://www.usgs.gov/staff-profiles/louis-sass",
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   {
     "@type": "Person",
     "name": "Caitlyn Florentine, Ph.D.",
     "url": "https://www.usgs.gov/staff-profiles/caitlyn-florentine",
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 "description": [
   {
     "@type": "TextObject",
     "text": "Nunatak weather station (Latitude 63\u00b017'N, Longitude 145\u00b026'W)"
   },
   {
     "@type": "TextObject",
     "text": "Return to Glaciers and Climate Project"
   },
   {
     "@type": "TextObject",
     "text": "Gulkana Glacier is located in the high-latitude continental climate regime of Alaska\u2019s Delta Mountains. Glacier observations began at this site in 1966."
   },
   {
     "@type": "TextObject",
     "text": "Additional Stations"
   },
   {
     "@type": "TextObject",
     "text": "The Phelan Creek near Paxson stream gaging station, USGS station 15478040, is part of the USGS network of nearly 100 stations in Alaska. Data collection and analysis are conducted by standard techniques developed by the USGS. Daily values of discharge are available online and published annually in the USGS Water-Data report series."
   },
   {
     "@type": "TextObject",
     "text": "Among other glaciological research, mass balance measurements of Gulkana Glacier began in the early 1960s with the University of Alaska Gulkana Glacier Project (P\u00e9w\u00e9 and Reger, 1983). In 1966 the USGS began direct measurements of surface mass balance, which, after a decade of dense spatial sampling, were reduced to three \"index\" sites distributed across the elevation range of Gulkana Glacier. Field visits to measure and maintain stakes at the three index sites are made each spring, at the onset of the melt season, and again in early autumn, near its completion. Density of the material gained or lost is measured with a snow-pit or core. By collecting data near the balance maxima and minima direct measurements closely reflect maximum winter accumulation and the annual balances at each location. Since 1975 both the stakes and the glacier surface elevations at the actual index sites have been surveyed to allow calculations of velocity and surface elevation change."
   },
   {
     "@type": "TextObject",
     "text": "Ridge-top weather station (Latitude 63\u00b018'N, Longitude 145\u00b024'W)"
   },
   {
     "@type": "TextObject",
     "text": "Liljedahl, A. et al., 2017, Glacierized headwater streams as aquifer recharge corridors, subarctic Alaska, Geophys. Res. Lett., 44, 6876\u20136885, doi:10.1002/2017GL073834."
   },
   {
     "@type": "TextObject",
     "text": "Since 1966, part of the Gulkana data set (net balance, accumulation, ablation, accumulation area ratio (AAR), and equilibrium line altitude (ELA)) has been published by the World Glacier Monitoring Service (Kasser, 1967; Muller, 1977; Haeberli, 1985; Haeberli and M\u00fcller, 1988; Haeberli and Hoelzle, 1993). Index-site glacier-surface and summer-surface altitudes, measured winter balance, and net firn and ice balance from 1975 to 1983 are reported by Mayo and Trabant (1986). Data for 1992 and 1993 were published by March and Trabant (1996 and 1997) and for 1994 by March (1998)."
   },
   {
     "@type": "TextObject",
     "text": "The original weather station had analogue instruments with strip-chart recorders. Daily average temperatures from that era have an accuracy of about \u00b11.0\u00b0C, and annual precipitation has an estimated accuracy of about \u00b10.005 m (Mayo and others, 1992; Kennedy, 1995). Daily precipitation records are complicated by thermal expansion of the antifreeze water solution. Starting in the late 1980's the station has been updated with progressively newer, more accurate, and more sensors."
   },
   {
     "@type": "TextObject",
     "text": "Gulkana Glacier is situated in the eastern Alaska Range of central Alaska, 200 miles north-east of Anchorage, Alaska. It sits in continental climate where precipitation tends to be lighter than in more coastal areas. Melt of glacial ice provides a seasonal input of cold, sediment-rich water to downstream rivers. Additionally, recent work has shown that melting glaciers increase streamflow in winter as well as summer, through contribution to aquifer recharge (Liljedahl, 2017). This impact has been demonstrated in glacier-fed headwater streams and larger lowland rivers, far downstream of initial glacial input. Glaciers in Interior Alaska are an important source of water to both streams and aquifers, as well as providing nutrients to downstream ecological communities."
   },
   {
     "@type": "TextObject",
     "text": "To increase the spatial distribution, two additional weather stations were placed higher in the basin in 2012 allowing researchers to directly measure lapse rates in each basin."
   },
   {
     "@type": "TextObject",
     "text": "Drainage Area: 32 km2"
   },
   {
     "@type": "TextObject",
     "text": "Nunatak is on bedrock between the main trunk and a western cirque at 1725 m. The sensors installed measure:"
   },
   {
     "@type": "TextObject",
     "text": "Gulkana Glacier is located along the south flank of the eastern Alaska Range. The climate is continental, characterized by a large range in temperatures, and irregular, lighter precipitation as compared to more coastal areas. The main trunk of the glacier has a southerly aspect, and is fed by four cirques with west, south, and east aspects. It spans 1300 m of elevation, from 1160 to 2470 m. The glacier is in a 31.5 km2 basin and in 2016 it had an area of 16.0 km2 (O'Neel et al, 2019)."
   },
   {
     "@type": "TextObject",
     "text": "Meteorological observations began in 1967 with installation of temperature and precipitation instruments near the moraine weather station. The addition and upgrading of sensors over the years have included measurement of precipitation (Sutron gauge) and new stations to directly measure lapse rates in each basin. The stations are telemetered for real time data acquisition."
   },
   {
     "@type": "TextObject",
     "text": "Current data available from the Gulkana weather station (USGS 15478038) includes:"
   },
   {
     "@type": "TextObject",
     "text": "Selected Publications:"
   },
   {
     "@type": "TextObject",
     "text": "Location: Latitude: 63\u00b014'27\"N, Longitude: 145\u00b028'03\"W., 1,125 m altitude, in SW 1/4 sec.28, T.19 S., R.12 E., Hydrologic Unit 19020102, on left bank about 1 km downstream from terminus of Gulkana Glacier and 23 km north of Paxson, Alaska."
   },
   {
     "@type": "TextObject",
     "text": "Ridge-top is north of the main trunk at 1925 m. The sensors installed measure:"
   },
   {
     "@type": "TextObject",
     "text": "The Gulkana weather station (latitude 63\u00b016'N, longitude 145\u00b025'W) is located at an altitude of 1480 m on the crest of a wind-swept, ice-cored moraine along the eastern boundary of the glacier. The station is slightly lower than the glacier's average equilibrium line altitude (ELA) and approximately 300 m from the east edge of the glacier. The average ELA is near 1,735m which is consistent with a continental mountain climate. The average annual air temperature at the recorder site is about -4 degrees Celsius(\u00b0C), and the average annual precipitation-gage catch is about 1,000 millimeters (mm). Snowfall is the dominant form of precipitation and usually accumulates on the glacier from September through mid-June. Daily average temperatures range from a low of -35\u00b0C to a high of 16\u00b0C. Daily precipitation catch can be over 100 mm."
   },
   {
     "@type": "TextObject",
     "text": "Period of Record: October 1966 to September 1978, October 1989 to September 1993, October 1994 to current year, and annual maximums, water years 1984-85. Before October 1968, published as Gulkana Creek near Paxson."
   },
   {
     "@type": "TextObject",
     "text": "In 1966 scientists with the USGS began collecting mass balance data on Gulkana Glacier, one of two \"benchmark glaciers\" in Alaska. Repeated point measurements at established index sites, in conjunction with local meteorology and runoff data, are used to estimate glacier-wide mass balances. These data constitute the longest continuous set of mass-balance data in North America (Josberger and others, 2007) which are used to understand glacier dynamics and hydrology, and understand the glacier's response to climate change."
   },
   {
     "@type": "TextObject",
     "text": "Direct field measurements are combined with weather data and imagery analyses to calculate the seasonal and annual mass balance of each glacier. Access all the data here."
   },
   {
     "@type": "TextObject",
     "text": "Gulkana Gaging Station Data (USGS 15478040):"
   },
   {
     "@type": "TextObject",
     "text": "NOTE: Records are poor. The creek bed is composed of typical ground-moraine material: poorly-sorted gravel and small boulders. The channel is subject to frequent changes during high flows. Large fluctuations result from ice melt and alternate damming and storage release during melt season. Typical winter under-ice discharge is about 0.1 m3/s; typical summer discharge is about 4-20 m3/s; the period-of-record peak discharge is 65 m3/s (Linn and others, 1994). The typical minimum winter under-ice discharge is about 0.04 m3/s, which is about three to four times the average contribution from the combined geothermal melt of the bed of the glacier and melting caused by the loss of potential energy from ice motion."
   },
   {
     "@type": "TextObject",
     "text": "Measurements began on Gulkana Glacier during the early 1960's with the University of Alaska Gulkana Glacier Project (P\u00e9w\u00e9 and Reger, 1983). For several years this project measured the energy budget, mass balance, meteorology, foliation, flow, and glacier bottom topography (from gravity anomalies) at Gulkana Glacier. In 1966, a continuing series of meteorological, snow and ice balance, and runoff measurements was begun by the USGS as part of the United States contribution to the International Hydrologic Decade study of mass balances on selected glaciers. Detailed results from 1966 and 1967 are reported by Meier and others (1971) and Tangborn and others (1977), respectively. Measured winter snow balances and annual balances from 1966-77 are reported by Meier and others (1980). Balance studies were relatively intensive until the mid-1970's, after which spatial sampling was reduced to three sites used as indices for mass balance. Measurements at the three remaining sites were expanded to include ice-motion and surface-altitude observations (for determining glacier-volume change) in addition to the balance, runoff, and meteorological observations already in progress."
   }
 ],
 "funder": {
   "@type": "Organization",
   "name": "Climate Research and Development Program",
   "url": "https://www.usgs.gov/programs/climate-research-and-development-program"
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