Firn Density and Stratigraphy Observations from USGS Benchmark Glaciers

Identification_Information:

Citation:

Citation_Information:

Originator: Stevens, C. Max (ORCID: 0000-0003-2005-0876)
Originator: Sass, Louis C. (ORCID: 0000-0003-4677-029X)
Originator: Florentine, Caitlyn E. (ORCID: 0000-0002-7028-0963)
Originator: Mcneil, Christopher J. (ORCID: 0000-0003-4170-0428)
Originator: Baker, Emily H. (ORCID: 0000-0002-0938-3496)
Originator: Bollen, Katherine E. (ORCID: 0000-0003-4345-0899)
Publication_Date: 20230719
Title:

Geospatial_Data_Presentation_Form: tabular digital data
Publication_Information:

Publication_Place: Anchorage, Alaska
Publisher: U.S. Geological Survey, Alaska Science Center

Other_Citation_Details:

Suggested Citation: Stevens, C.M., Sass,L.C., Florentine, C.E., Mcneil, C.J., Baker, E.H., Bollen, K.E., 2023, Firn density and stratigraphy observations from USGS Benchmark Glaciers: U.S. Geological Survey data release, https://doi.org/10.5066/F7610XHQ

Online_Linkage: https://doi.org/10.5066/F7610XHQ
Larger_Work_Citation:

Citation_Information:

Originator: U.S. Geological Survey Benchmark Glacier Program
Publication_Date: 2020
Title: USGS Benchmark Glacier Project Comprehensive Data Collection
Geospatial_Data_Presentation_Form: dataset
Publication_Information:

Publication_Place: Anchorage, Alaska
Publisher: U.S. Geological Survey

Other_Citation_Details:

U.S. Geological Survey Benchmark Glacier Program, 2020, USGS benchmark glacier project comprehensive data collection: U.S. Geological Survey data release, https://doi.org/10.5066/P9AGXQSR

Online_Linkage: https://doi.org/10.5066/P9AGXQSR

Description:

Abstract:

This dataset contains observations of snow and firn density and stratigraphy from Site EC on Wolverine Glacier. Site EC is located in the accumulation zone on the northwest flank of the upper glacier at 1350m. Cores were recovered using a FELICS corer to approximately 25m depth at the end of the accumulation season and the end of ablation season starting in 2016. Additional cores were drilled throughout the ablation seasons of 2016 and 2017. The cores were processed in the field. The dataset includes depth-density profiles, ice-lens stratigraphy, and annual-layer depths. Density was calculated by measuring the mass and length of each core section (the corer retrieves cores with uniform diameter, which was measured on randomly selected core sections). Ice lenses were identified by visual inspection. Annual layer depths were determined by identifying dark layers in the core, which are interpreted to be the end-of-melt-season surfaces.

Purpose:

This collection of data is used to quantitatively record changes in firn and snow properties on Wolverine Glacier over the period of record. These data were primarily collected for the purpose of understanding how firn processes affect glacier mass balance. There are many other potential uses for this data, including improving understating of firn evolution, remote sensing validation, and/or water resource applications. Data are included as available through the history of the firn coring project on Wolverine Glacier. Additional information is included in the README file.

Time_Period_of_Content:

Time_Period_Information:

Range_of_Dates/Times:

Beginning_Date: 2016
Ending_Date: 2022

Currentness_Reference: observed

Status:

Progress: Complete
Maintenance_and_Update_Frequency: As needed

Spatial_Domain:

Bounding_Coordinates:

West_Bounding_Coordinate: -148.9142
East_Bounding_Coordinate: -148.9141
North_Bounding_Coordinate: 60.4261
South_Bounding_Coordinate: 60.4260

Keywords:

Theme:

Theme_Keyword_Thesaurus: USGS Metadata Identifier
Theme_Keyword: USGS:ASC545

Theme:

Theme_Keyword_Thesaurus: ISO 19115 Topic Category
Theme_Keyword: geoscientificInformation

Theme:

Theme_Keyword_Thesaurus: NASA GCMD Earth Science Thesaurus
Theme_Keyword: Cryosphere
Theme_Keyword: Glaciers/Ice Sheets
Theme_Keyword: Glaciers
Theme_Keyword: Ablation Zones/Accumulation Zones
Theme_Keyword: Glacier Mass Balance/Ice Sheet Mass Balance

Theme:

Theme_Keyword_Thesaurus: USGS CSA Biocomplexity Thesaurus
Theme_Keyword: Glaciology

Theme:

Theme_Keyword_Thesaurus: USGS Thesaurus
Theme_Keyword: Snow and ice cover
Theme_Keyword: Glaciation
Theme_Keyword: Glaciology

Theme:

Theme_Keyword_Thesaurus: None
Theme_Keyword: Geophysics

Place:

Place_Keyword_Thesaurus: USGS Geographic Names Information System (GNIS)
Place_Keyword: Wolverine Glacier
Place_Keyword: Alaska

Access_Constraints: None
Use_Constraints:

It is requested that the authors and the USGS be cited for any subsequent publications that reference this dataset.

Point_of_Contact:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization: U.S. Geological Survey, Alaska Science Center

Contact_Address:

Address_Type: Mailing and Physical
Address: 4210 University Drive
City: Anchorage
State_or_Province: Alaska
Postal_Code: 99508
Country: USA

Contact_Voice_Telephone: 907-786-7000
Contact_Electronic_Mail_Address: ascweb@usgs.gov

Cross_Reference:

Citation_Information:

Originator: USGS Glaciers and Climate Group
Publication_Date: 2018
Title: Alaska Benchmark Glacier Mass Balance Website
Geospatial_Data_Presentation_Form: website
Publication_Information:

Publication_Place: online
Publisher: U.S. Geological Survey

Other_Citation_Details: USGS Glaciology Studies information website
Online_Linkage: https://doi.org/10.5066/P9AGXQSR

Data_Quality_Information:

Attribute_Accuracy:

Attribute_Accuracy_Report:

Uncertainties in the measurements are not well constrained but can be estimated. Each core section's mass and length was measured. Mass measurement resolution is estimated to be +/-5 g, based on the resolution of the scale. Some mass measurements could be biased high because of drill shavings that can stick to the outside of the core.

Length measurements are estimated to be +/-1 cm. This uncertainty stems mostly from core breaks that are not exactly perpendicular to the core axis.

Core diameter is only measured on random sections of core, but the corer consistently produces cores with a diameter of 5.7 cm, and we estimate that +/- 0.1 cm is a reasonable uncertainty bound.

Some core sections have very uneven core breaks or portions of core missing (e.g., where the core dogs chewed into the core). We have made our best effort to note these sections. These core sections have larger uncertainties in their densities. In general, the volume of material missing can be estimated to be less than 10% of the total volume of the core section.

Ice lens stratigraphy recording has used two different methods during the project; in some cases, the thickness and position of each ice lens was recorded, and in others the total thickness of ice within a core section was recorded. In some cases, ice lens positions were not recorded. When ice lenses were recorded, a conservative uncertainty estimate is to assume that the ice lens is somewhere within the particular length of core.

Annual layer depths are estimated to be accurate to +/-1 cm. The year of the annual layer is certain unless noted otherwise in the comments.

Logical_Consistency_Report:

The data release is derived from original spreadsheets in which field notes were transcribed. Data have been QA/QC'd by hand. Any inconsistencies or outlying data were checked against field notebooks. However, errors in the data may remain.

Completeness_Report:

We include all digitized firn core data; additional information may be available via digital scans of field notebooks.

Positional_Accuracy:

Horizontal_Positional_Accuracy:

Horizontal_Positional_Accuracy_Report:

All firn cores were drilled at the same location. The coordinates for Site EC on Wolverine Glacier are UTM zone 6N, E394619, N6700393. The location was found using handheld GPS or mobile phone, and the estimated accuracy in horizontal position is 5 m.

Lineage:

Process_Step:

Process_Description:

Field Measurements: For end-of-accumulation season measurements, a snow pit is dug to approximately 1 m depth. Density of the snow pit is measured using a 1000cc SnowMetrics cutter on the snow pit wall. Coring is commenced from the bottom of the snow pit. At the end of the ablation season, coring is commenced from the surface.

Each corer drive retrieves some length of snow/firn core. If the retrieved core is long, it is broken into sections of approximately 30 cm. The core section's length is measured using a tape measure and then it is weighed. The diameter of random sections is measured to ensure that the corer is retrieving uniform cores. If the core is missing some material (e.g., due to core dogs or an uneven core break) a note is made in the field notebook.

The core is then visually inspected for ice lenses and annual layers. Ice lens depth and thickness are recorded. In some years, each core section's total ice lens thickness was recorded, which allows a density correction for the firn in that section but does not identify depths of individual lenses. In other years, the thickness and position of individual lenses were recorded. In some cases ice lens stratigraphy was not recorded.

Annual layers are identified by darker layers within the firn, which are assumed to be end-of-melt-season surfaces. The year of the annual layer is determined by either counting backward or considering the mass of firn between identified annual layers. These layers are often difficult to identify, and so not all cores have annual layers identified.

Finally, the depth of the borehole is measured using a tape measure after each coring drive.

Process_Date: Unknown

Process_Step:

Process_Description:

Post processing: The post processing routine first calculates sample density. Then, layer boundaries are calculated. These may not be the same as the depths of the sample top and bottom due to small measurement discrepancies. If the measured borehole depth and the core length do not agree, the layer bottom and layer top fields are determined by taking the mean of the two. (See README file for more detail.) The sample density is assigned to be the layer density. The, we calculate layer snow-water equivalent (SWE), cumulative (from the surface) density and SWE, and density of the firn excluding ice lenses if lenses were present.

Process_Date: 20230406

Entity_and_Attribute_Information:

Detailed_Description:

Entity_Type:

Entity_Type_Label: [GLACIER]_[SITE]_firn_[DATE].csv
Entity_Type_Definition:

Folder containing tables of data from firn cores taken on different dates. Firn core measurements include depth-density profiles, ice-lens stratigraphy, and annual-layer depths. Density was calculated by measuring the mass and volume of each core section. Ice lenses were identified by visual inspection. Annual layer depths were determined by identifying dark layers in the core, which are interpreted to be the end-of-melt-season surfaces. Missing data or no data are left blank. Presented in a Comma Separated Value (CSV) formatted table.

All firn cores were drilled at the same location. The coordinates for Site EC on Wolverine Glacier are UTM zone 6N, E394619, N6700393.

File naming convention: [GLACIER]_[SITE]_firn_[DATE]: where [GLACIER] = glacier name; [SITE] = observation site on glacier; [DATE] = sampling date (yyyy.mm.dd)

Entity_Type_Definition_Source: Author defined

Attribute:

Attribute_Label: SBD
Attribute_Definition:

Sample Bottom Depth. The measured depth at the bottom of borehole after each core drive. For core drives that had more than one core section, SBD is determined by subtracting the section length from the measured SBD.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain: Sample Bottom Depth measured in centimeters (cm).

Attribute:

Attribute_Label: mass
Attribute_Definition: Mass of the core section or sample.
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain: Mass of the core section or sample measured in grams (g).

Attribute:

Attribute_Label: length
Attribute_Definition:

Length of the core section. In some campaigns the core was measured to 0.1 cm resolution and in other to 0.5 cm resolution.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain: Length of the core section measured in centimeters (cm).

Attribute:

Attribute_Label: diameter
Attribute_Definition:

Diameter of the core section. The FELICS corer generally recovers core with a 5.7 cm diameter. Random core sections are measured to verify the consistency of this measurement. Blank cells indicate that density measurements on snow pit walls with the cutter do not have a diameter.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain: Diameter of the core section measured in centimeters (cm).

Attribute:

Attribute_Label: volume
Attribute_Definition:

Volume of the sample (core section or snow recovered with wedge cutter). For core sections, this value is derived from the core length and diameter. The volume of the wedge cutter is known.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain: Volume of the sample measured in cubic centimeters (cm^3).

Attribute:

Attribute_Label: layer_top
Attribute_Definition: Depth of the top of the snow/firn layer that is sampled.
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain:

Depth of the top of the snow/firn layer measured in centimeters (cm).

Attribute:

Attribute_Label: layer_bottom
Attribute_Definition: Depth of the bottom of the snow/firn layer that is sampled.
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain:

Depth of the bottom of the snow/firn layer measured in centimeters (cm).

Attribute:

Attribute_Label: layer_density
Attribute_Definition: Density of the layer.
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain:

Density of the layer measured in grams per cubic centimeters (g cm^-3).

Attribute:

Attribute_Label: layer_SWE
Attribute_Definition: Snow-water equivalent of the layer.
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain:

Snow-water equivalent of the layer measured in meters water equivalent (m w.e.).

Attribute:

Attribute_Label: cumulative_density
Attribute_Definition:

The cumulative density of the snow and firn to the layer_bottom.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain:

The cumulative density of the snow and firn to the layer_bottom measured in grams per cubic centimeter (g cm^-3).

Attribute:

Attribute_Label: cumulative_SWE
Attribute_Definition:

The cumulative snow-water equivalent of the snow and firn to the layer_bottom.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain:

The cumulative snow-water equivalent of the snow and firn to the layer_bottom measured in meters water equivalent (m w.e.).

Attribute:

Attribute_Label: ice_lens_height_all
Attribute_Definition:

The height of the bottoms of each observed ice lens relative to the layer_bottom. If multiple ice lenses were observed in the core section, this is a series of values separated by commas. Blank cells indicate no ice lens in the core section.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain:

The height of the bottoms of each observed ice lens relative to the layer_bottom measured in centimeters (cm).

Attribute:

Attribute_Label: ice_lens_thick_all
Attribute_Definition:

The thickness of each observed ice lens, corresponding to ice_layer_height_all. If multiple ice lenses were observed in the core section, this is a series of values separated by commas. Blank cells indicate no ice lens in the core section.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain:

The thickness of each observed ice lens measured in centimeters (cm).

Attribute:

Attribute_Label: ice_lens_height_sum
Attribute_Definition:

The height of the bottom of the lowest (closest to the layer bottom) lens if multiple ice lenses were observed, or height of bottom of ice lens if there was a single ice lens. Blank cells indicate no ice lens in the core section.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain:

The height of the bottom of the lowest lens measured in centimeters (cm).

Attribute:

Attribute_Label: ice_lens_thick_sum
Attribute_Definition:

Summed thickness of all ice lenses in the layer. Blank cells indicate no ice lens in the core section.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain:

Summed thickness of all ice lenses in the layer measured in centimeters (cm).

Attribute:

Attribute_Label: density_no_ice
Attribute_Definition:

Density of just the snow/firn in the layer if ice lenses were present, assuming an ice density of 0.9 g cm^-3.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain:

Density of just the snow/firn in the layer measured in grams per cubic centimeter (g cm^-3).

Attribute:

Attribute_Label: annual_layer_depth
Attribute_Definition:

Depth of annual layers below surface. Blank cells indicate that there was no identified annual layer in the core section.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain:

Depth of annual layers below surface measured in centimeters (cm).

Attribute:

Attribute_Label: annual_layer_year
Attribute_Definition:

Year of the annual layer. Blank cells indicate that there was no identified annual layer in the core section.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain: Year (YYYY) of the annual layer.

Attribute:

Attribute_Label: LWC
Attribute_Definition:

Percent Liquid water content. Blank cells indicates no measurement taken.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain: Percent Liquid water content (%).

Attribute:

Attribute_Label: temperature
Attribute_Definition:

Snow/firn temperature. Blank cells indicates no measurement taken.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain: Snow/firn temperature measured in degrees Celsius (C)

Attribute:

Attribute_Label: grain_size
Attribute_Definition: Average grain size. Blank cells indicates no measurement taken.
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain: Average grain size measured in millimeters (mm)

Attribute:

Attribute_Label: measurement_type
Attribute_Definition: Whether the measurement is from a snow pit (P) or a core (C)
Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Enumerated_Domain:

Enumerated_Domain_Value: P
Enumerated_Domain_Value_Definition: Measurement from a snow pit.
Enumerated_Domain_Value_Definition_Source: Author defined

Attribute_Domain_Values:

Enumerated_Domain:

Enumerated_Domain_Value: C
Enumerated_Domain_Value_Definition: Measurement from a core section
Enumerated_Domain_Value_Definition_Source: Author defined

Attribute:

Attribute_Label: Comments
Attribute_Definition:

Any comments about the core section or other germane notes about the methodology.

Attribute_Definition_Source: Author defined
Attribute_Domain_Values:

Unrepresentable_Domain: Comments are entered as strings.

Firn Density and Stratigraphy Observations from USGS Benchmark Glaciers

Metadata: