Glacier-Wide Mass Balance and Compiled Data Inputs

Table of yearly glacier geometry provided as Area Altitude Distribution (AAD). Columns represent area in 100 m elevation bins, except Sperry Glacier which uses 30 m bins, and South Cascade Glacier which uses 50 m bins. The area in each bin is given in km2. The first row is a column header and specifies the median elevation for the bin. The first column gives the balance year that the areas represent. The total glacier area can be calculated by summing across the row for any given year. Glacier areas are derived from DEMS constructed in a number of years, and area is interpolated linearly between DEM acquisitions. Presented in a Comma Separated Value (CSV) formatted table. File naming convention: Input_[GLACIER]_Area_Altitude_Distribution: where [GLACIER] = glacier name

Table with daily meteorological observations. Precipitation is given in millimeter water equivalent (mm.w.e.) and temperature in degrees Celsius. Precipitation values represent daily totals and temperature values represent daily averages of all temperatures recorded. Presented in a Comma Separated Value (CSV) formatted table. Detailed information on specific stations, and sub-daily data beginning in the 1990s at the analog-digital transition is available in an associated weather data release, available under the USGS Benchmark Glacier Mass Balance and Project Data collection via https://doi.org/10.5066/F7BG2N8R. In glacier-wide analyses, meteorological stations installed within the glacier watershed are used at Wolverine and Gulkana glaciers. Discontinuous local records for South Cascade Glacier, Lemon Creek Glacier, and Sperry Glacier prompted use of continuously-operating area weather stations. Portions of this discontinuous, local station data is available in the associated weather data release. Locations of weather stations used for calculation of glacier-wide mass balance are given below. Wolverine 990: 60.3819, -148.9397 Gulkana 1480: 63.2614, -145.4102 Lemon Creek 5: 58.3566, -134.564 South Cascade 270: 48.7141, -121.143 Sperry 1920: 48.8017, -113.857 Location of primary weather station used for each glacier. Gulkana and Wolverine are within the glacier basin; others are continuously-operating weather stations in the area of the glacier. Coordinates are given in decimal degrees; elevations are in meters. To produce glacier-wide mass balance solutions, these weather data are used to solve for the timing of mass extrema. The USGS uses data from Seward, AK to fill data gaps in the Wolverine glacier meteorology record (van Beusekom and others, 2010). Gaps in the Gulkana record are filled with data from the Gulkana Airport in Glenallen, AK. In Montana, near Sperry Glacier, data gaps from the Flattop SNOTEL are filled with data from the Hungry Horse Dam. Time series from the Juneau Airport for Lemon Creek and Diablo Dam for South Cascade are not filled with data from a secondary site. Prior to Version 5.0, a lapse rate of -6.5 C/km was used to calculate on-glacier temperatures across at all Benchmark Glaciers. In Version 5.0 forward, using local weather stations the Lemon Creek Glacier lapse rate was optimized, resulting in a -5.0 C/km lapse rate as detailed in McNeil and others 2020, "Explaining mass balance and retreat dichotomies at Taku and Lemon Creek Glaciers, Alaska". Mass balance estimates rely on the relationship between winter precipitation observed at a weather station, and snow/ice observed on the ground during spring mass balance measurements and the balance profile. Additional years of data allow for further refinement of this relationship, which changes the historical time series very slightly with each additional year of data. File naming convention: Input_[GLACIER]_Daily_Weather: where [GLACIER] = glacier name

Table of site names of all Mass Balance Index Sites and their geographic coordinates (UTM). Presented in a Comma Separated Value (CSV) formatted table. File naming convention: [GLACIER]_UTM[zone]: where [GLACIER] = glacier name, [zone] = UTM zone

Table with time series of point water balances measurements. Presented in a Comma Separated Value (CSV) formatted table. File naming convention: Input_[GLACIER]_Glaciological_Data: where [GLACIER] = glacier name

Table with both annual and seasonally time-stepped glacier-wide mass balance solutions calibrated with geodetic observations (O'Neel and others, 2014). Presented in a Comma Separated Value (CSV) formatted table. These results are produced using a two-piece linear balance profile based on elevation. This two-piece balance profile was chosen because it incorporates physical expectations of variable melt rates for snow and ice. Our choice was guided by several factors including: 1) feasibility and goodness-of-fit at all glaciers, 2) applicability for both sparse and robust data sets, and 3) capacity to include short-lived expanded stake and ground-penetrating radar campaigns above long-term index sites. Each fit is constrained to have a single interior breakpoint, or knot, in the piecewise-linear fit. Further details are given in O'Neel and others, 2019. Prior to version 3.0 of this data release, values were calculated using the "index method" (van Beusekom and others, 2010). Version 3.0 of this data release results from a significant reanalysis effort, detailed in O'Neel and others, 2019. Calibration: USGS follows much of the re-analysis procedure outlined by Zemp and others (2013). However, for geodetic calibration, we adopt a piecewise/ breakpoint fitting approach over approximately decadal intervals. This maximizes the incorporation of geodetic data, while minimizing the impacts of non-stationarity that manifest in multi-decadal calibrations, and limits the impact of errors arising from material density assumptions. For further details, see O'Neel (2019). Associated geodetic data used to derive the calibrations are given in an accompanying data release, found under the USGS Benchmark Glacier Mass Balance and Project Data collection via https://doi.org/10.5066/F7BG2N8R File naming convention: Output_[GLACIER]_Glacier_Wide_solutions_calibrated: where [GLACIER] = glacier name

Table of transient snow line data. Presented in a Comma Separated Value (CSV) formatted table. *Note that TSL data is not provided for all glaciers in this data release. File naming convention: Input_[GLACIER]_TSL_Data: where [GLACIER] = glacier name

Table with sub-seasonal glaciological data. Presented in a Comma Separated Value (CSV) formatted table. *Note that sub-seasonal data is not provided for all glaciers in this data release. File naming convention: Input_[GLACIER]_SubSeasonal_Glaciological_Data: where [GLACIER] = glacier name

Table with geodetic summary data. Presented in a Comma Separated Value (CSV) formatted table. File naming convention: Input_[GLACIER]_Geodetics: where [GLACIER] = glacier name

Table with a list of contributors to the data collection at each glacier each year. Presented in a Comma Separated Value (CSV) formatted table.