Lemon Creek Glacier Active

Sources/Usage: Public Domain.

Lemon Creek Glacier is located at the southernmost tip of the Juneau Icefield in Southeast Alaska, USA, approximately 6.5 km northeast of the city of Juneau. It is a subarctic alpine glacier in a maritime climate. The glacier flows northward from its accumulation zone and spans 900 m of elevation, from approximately 600 to 1500 m. Lemon Creek Glacier is in a 31.9 km² basin and had an area of 9.7 km² in 2018 (O'Neel et al, 2019).

In 1957/58, Lemon Creek Glacier was chosen as a representative glacier for the 1957/58 International Geophysical Year and it continues to serve as a reference glacier of the World Glacier Monitoring Service.

Lemon Creek Glacier is geographically situated between glaciers in the contiguous USA and those in mainland Alaska. This strategic location and existing long term data set prompted the USGS to align protocols and mass balance analysis with the other four USGS Benchmark Glaciers in 2013.

Research

Sources/Usage: Public Domain.

Glacier mass balance

Mass balance measurements began at Lemon Creek Glacier in 1953, under the direction of the Juneau Icefield Research Program (JIRP). These data represent the second longest continuous annual record of mass balance in North America, consisting mostly of annual late-season accumulation observations. Around 1970 a network of four standard measurement sites were established across an elevation gradient and standard methods of mass balance measurement were implemented at snow pits and along ablation transects (Pelto and others, 2013). In 2013, additional measurements were added to complement the USGS Benchmark Glacier research protocol which includes two field visits per year to capture the range of mass balance (O’Neel, and others, 2019). These visits to measure and maintain stakes at the 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.

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.

Meteorologic

Sources/Usage: Public Domain.

Measurements of air temperature data have been collected at many permanent camp facilities and along the margins of Lemon Creek Glacier for use in mass balance calculations for the period of record 1990-2018. These data are available through the Alaska Science Center Data Repository for the following parameters:

• Temperature, air (1998 - present)

Gaps in data and challenges with instrumentation over the decades have also required the use of nonlocal meteorological data from the nearby Juneau Airport (ncdc.noaa.gov, Station ID: USW00025309) for mass balance calculations. The airport is located at sea-level, 13 km from the glacier. The data from the Juneau airport were used in the 2019 reanalysis and are available here.

Hydrologic

The Lemon Creek near Juneau stream gaging station, USGS station 15052000, 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. Water data back to 1948 exists of the USGS Lemon Creek Gaging Station web page.

Lemon Creek Gaging Station Data (USGS 15052000):

• Temperature, air (available 2019-08-18 to current)
• Temperature, water (available 2017-11-09 to current)
• Stream Discharge (available 2002-05-08 to current)
• Gage Height (available 2007-10-18 to current)

Location: Latitude: 58°23'30"N, Longitude: 134°25'15 NAD27, City And Borough Of Juneau, Alaska, Hydrologic Unit 19010301, Datum of gage: 204 m above NAVD88.

Drainage Area: 32 km²

Period of Record: August 1951 to current year (discharge data), Field/lab water quality data Oct 1948 to current year.

Sources/Usage: Public Domain.

Previous Work

Because of its ease of access and its designation as a one of nine representative glaciers for the 1957/58 International Geophysical Year, Lemon Creek Glacier has been extensively studied over the decades. The data are reported to the World Glacier Monitoring Service (WGMS) annually. Field observations were initiated in 1953, under the direction of the Juneau Icefield Research Program (JIRP). Seasonal measurements and a consistent network of snowpit sites were added to the protocol in 2016 to align methodology with the other benchmark glaciers. Reanalysis of the five USGS Benchmark Glaciers (including Lemon Creek) was published by O’Neil et al (2019) and underscored the importance of using geodetic calibration to evaluate mass-balance trends based on the direct glacier measurements.