Mass Balance Submission Guide

Mass Balance Submission Guide

This page describes the experimental protocol for the IMBIE Mass Balance Inter-
comparison, including details on participation conditions and data formats to use. This inter-comparison aims at (i) comparing estimates of ice sheet mass balance derived from different satellite techniques to assess their level of agreement and (ii) aggregating these estimates to provide a reconciled time-series of mass changes of Greenland and Antarctica.

Experimental Protocol

To compare and aggregate ice sheet mass balance estimates, we will follow the same methods as previous IMBIE assessments. We are hoping to make some methodological improvements but the main steps will remain the same. We will (i) compute dM(t)/dt for all datasets that were submitted as dM(t), (ii) aggregate the time series of mass trends within each class of satellite observations, (iii) combine the altimetry, gravimetry, and input–output time series to derive a single reconciled time series of mass trends, and (iv) integrate this reconciled time series of mass trends to produce the final reconciled time series of cumulative mass change.

Participation Conditions

You must contribute a unique data set that you or your team has created to one of our three experiment groups (Altimetry, Gravimetry, or Mass Budget).

Submissions must be based on satellite observations of changes in the volume, flow, or gravitational attraction of the ice sheets (estimates derived from DEM differencing can be submitted through the altimetry group).
We currently cannot accept mass balance solutions derived from the combination of several techniques.
You are only allowed to submit one dataset to each experimental group.

The methods you employ and their errors must have been fully described in an international peer-reviewed journal or, in exceptional circumstances, in an accompanying document that will be subject to peer review by the IMBIE Executive Committee.
You are also expected to play an active role in the exercise, remaining in timely correspondence with the project coordinators when required.
The creators of any data incorporated into future IMBIE assessments will be consulted and involved throughout the whole process.
We will endeavour to include all suitable data submitted into a future publication.

Standard Format

We have defined standard file formats to simplify data collection. Please note that the standard file formats are different from the ones used in previous IMBIE assessments to help identify ambiguous entries, which were previously difficult to detect.

We now require strict format and parameter value compliance, which we automatically check when you upload the file. Performing stricter initial checks will help us reduce potential post-processing issues, and focus our efforts on the final mass balance analysis.

Participants can submit either a time-series of mass change, a time-series of mass trends, or both. If you submit just the mass change time-series file, we will generate the corresponding mass rates file for you. You may prefer that your own method of converting mass change to mass rates and integrating their uncertainties is used. If this is the case, please submit the mass rates file.

The following file types apply for Altimetry, Gravimetry and Mass Budget submissions:

Type	Description	Format
Time-series of Mass Change	Single file containing dM(t), uncertainty, and area stats, including all your chosen submitted regions and basins of AIS and/or GrIS	10-column CSV
Rates of Mass Change	Single file containing dM/dt, uncertainty and area stats, including all your chosen submitted regions and basins of AIS and/or GrIS	11-column CSV

Please also make sure that:

For each drainage basin or ice sheet region include one row per available measurement time of mass change.
Only one file can be submitted, so include all your areas for Antarctica and/or Greenland in this file.
If you provide time-series for all the basins that make up an ice sheet, please also provide the total mass change time-series for the corresponding ice sheet in the file. So, for example, if you provide a time-series (multiple rows) for each of the 18 Antarctic drainage basins, also provide a time-series (multiple rows) for regions ‘AIS’, ‘EAIS’, ‘WAIS’, and ‘APIS’. Similarly, if you provide a time-series for each of the 7 Greenland regions, please also provide a time-series for region ‘GRIS’ (multiple rows). The description of the drainage basins can be found here.[IO1]
If you provide time-series for the peripheral ice cap and glaciers, please note that these will need to be distributed across the 18 Antarctic drainage basins and 7 Greenland regions. The description of the drainage basins can be found here [IO2] .

General CSV File Requirements

IMBIE-3 file CSV file formats have the following general requirements, some of which are new in IMBIE-3:

CSV format file names must end in .csv (we do not accept any other end strings such as .txt).
CSV files should use UTF-8 character encoding (this is normally the default used by most modern programming languages).
A single line header is optional, but recommended to label your columns. (ie surname, group, ice_sheet, …). We ignore this line if it is present, but it can be useful if we need to investigate any anomalies in your file.
CSV format files must contain comma separated values or strings. (ie String,Value,Value,…). No other delimiters are allowed.
You may leave spaces either side of a string or value, but not in the middle of a string unless a multi-word string is expected. ie spacing such as : String, Value, Value ,… is allowed.
Comment lines are allowed anywhere in the file. These lines must start with a # character as the first character. We ignore these lines.
CSV files must not contain additional columns. The number of columns and the column order must exactly match the specification below.
You must not include commas or any special characters (*/\’”_+) in your values or strings unless explicitly allowed below.
Positive numerical values should not include the + sign.
Floating point numbers should be represented by standard (not exponential) numbering. ie 123456.0 and not 1.234560+e05
Do not include any commas in numerical values. ie use 10000 and not 10,000.
Empty column entries are not allowed unless explicitly specified in the format description.
Do not include NaN values.
Time-series of mass change

The Mass Time Series CSV file is comprised of exactly 10 comma separated columns in the order shown. Do not include an index (column number) column. Note that the number of columns has increased since IMBIE-3 with an additional column inserted.

Each data row of the .csv file must contain the following columns:

Column Number	Column Name	Description	Allowed Values
1	surname	Surname of lead author	Single word string with no space characters between words. You may include a hyphen – character, but do not include special characters [* _ /]. Only include the lead author of the data. You can attribute other authors in the submission questions.
2	group	Experiment group name.	A string containing one of ‘Altimetry’, ‘Gravimetry’, or ‘Mass Budget’. Do not include the quote marks. Do include the space character between Mass and Budget. These are case sensitive, so ‘altimetry’ will not be accepted. All column 2 entries in the file must be the same. You cannot have more than one group in the file.
3	ice_sheet	Area of this row is contained within Antarctica or Greenland	A string containing one of ‘Antarctica’, or ‘Greenland’. Do not include the quote marks. Case sensitive. Note that this is a new column in IMBIE-3.
4	surface_type	Surface type (ice_sheet, ice_cap or both)	A string containing one of ‘ice_sheet, ‘ice_cap’, ‘both’. Do not include the quote marks. Case sensitive. If you cannot separate between the ice sheet and its peripheral glaciers and ice caps (for instance if you are using gravimetry), then please select ‘both’. Note that this is a new column in IMBIE-3.
5	region_id	Drainage Region ID	A single string containing one of the strings shown below within the quote marks (do not include the quote marks). Please take care to be exact. Rignot Antarctic basins: ‘H-Hp’, ‘F-G’, ‘E-Ep’, ‘D-Dp’, ‘Cp-D’, ‘B-C’, ‘A-Ap’, ‘Jpp-K’, ‘G-H’, ‘Dp-E’, ‘Ap-B’, ‘C-Cp’, ‘K-A’, ‘J-Jpp’, ‘Ipp-J’, ‘I-Ipp’, ‘Hp-I’, ‘Ep-F’, or Rignot Antarctic regions: ‘AIS’, ‘EAIS’, ‘WAIS’, ‘APIS’, or Mouginot Greenland regions: ‘NO’, ‘NE’, ‘SE’, ‘SW’, ‘CW’, ‘NW’, or Mouginot Greenland regions: ‘GRIS’ Note in particular that the Greenland ice sheet is specified by ‘GRIS’ only (not GIS, GrIS, etc.)These are all case sensitive. Do not zero pad basin strings with numerical values ie ’01’ instead of ‘1’. Please take care to get these strings exact. For more information on the drainage basins used please see this link.[IO3]
6	area	Drainage Region Area (in square kilometres). This is the full area of the region chosen in column 5.	A numerical value in units of km². Float or Integer, ie ‘11892542’ or ‘11892542.0’. Do not include units, other text or the quote marks. Do not use exponential formats such as: ‘1.1892542e+06’. Do not use commas in the number such as ‘11,892,542’
7	area_observed	Drainage Region Area Observed by your satellite dataset (in square kilometres). This is area of the region chosen in column 5 that is actually observed and may be less than the full area in column 6.	A numerical value in units of Km2. Float or Integer, i.e. ‘11892542’ or ‘11892542.0’. Do not include units, other text or the quote marks. Do not use exponential formats such as: 1.1892542e+06.Do not use commas in the number such as ‘11,892,542’
8	date	Date for this entry in your time series (in decimal years).	A numerical value in units of years in the format ‘YYYY.yy’. Float, i.e. ‘1991.23’ or ‘2023.96’. Do not include units, other text or the quote marks.
9	mass_change	the Relative Mass Change for each entry in your time series (in gigatons).	A numerical value in units of gigatons. Float, i.e. ‘-100.45’ or ‘303.76’ Do not include units, other text or the quote marks. Do not include the ‘+’ character.
10	mass_change_uncert	Relative Mass Change Uncertainty for each entry in your time series (in gigatons).	A numerical value in units of gigatons. Float, i.e. ‘-100.45’ or ‘303.76’ Do not include units, other text or the quote marks. Do not include the ‘+’ character.

Time-series of mass trends

Please provide discrete rates of mass change (no overlapping time intervals) at the finest temporal resolution afforded by your dataset, preferably over monthly epochs. If you submit annual rates of mass change, please provide rates calculated over calendar years (from 1^st January to 31^st December).

The rate of mass change CSV file is comprised of exactly 11 comma separated columns in the order shown. Do not include an index (column number) column. Note that the number of columns has increased since IMBIE-3 with an additional column inserted

Each data row of the .csv file must contain the following columns:

Column Number	Column Name	Description	Allowed Values
1	surname	Surname of lead author	Single word string with no space characters between words. You may include a hyphen – character, but do not include special characters [* _ /]. Only include the lead author of the data. You can attribute other authors in the submission questions.
2	group	Experiment group name.	A string containing one of ‘Altimetry’, ‘Gravimetry’, or ‘Mass Budget’. Do not include the quote marks. Do include the space character between Mass and Budget. These are case sensitive, so ‘altimetry’ will not be accepted. All column 2 entries in the file must be the same. You cannot have more than one group in the file.
3	ice_sheet	Area of this row is contained within Antarctica or Greenland	A string containing one of ‘Antarctica’, or ‘Greenland’. Do not include the quote marks. Case sensitive. Note that this is a new column in IMBIE-3.
4	surface_type	Surface type (ice_sheet, ice_cap or both)	A string containing one of ‘ice_sheet, ‘ice_cap’, ‘both’. Do not include the quote marks. Case sensitive. If you cannot separate between the ice sheet and its peripheral glaciers and ice caps (for instance if you are using gravimetry), then please select ‘both’. Note that this is a new column in IMBIE-3.
5	region_id	Drainage Region ID	A single string containing one of the strings shown below within the quote marks: Rignot Antarctic basins: ‘H-Hp’, ‘F-G’, ‘E-Ep’, ‘D-Dp’, ‘Cp-D’, ‘B-C’, ‘A-Ap’, ‘Jpp-K’, ‘G-H’, ‘Dp-E’, ‘Ap-B’, ‘C-Cp’, ‘K-A’, ‘J-Jpp’, ‘Ipp-J’, ‘I-Ipp’, ‘Hp-I’, ‘Ep-F’, or Rignot Antarctic regions: ‘AIS’, ‘EAIS’, ‘WAIS’, ‘APIS’, or Mouginot Greenland regions : ‘GRIS’, or Mouginot Greenland regions: ‘NO’, ‘NE’, ‘SE’, ‘SW’, ‘CW’, ‘NW’, or Mouginot Greenland regions: ‘GRIS’ Do not include the quote marks. Case sensitive. Do not zero pad basin strings with numerical values ie ’01’ instead of ‘1’. Please take care to get these strings exact. For more information on the drainage basins used please see this link.[IO4]
6	area	Drainage Region Area (in square kilometres). This is the full area of the region chosen in column 5.	A numerical value in units of km². Float or Integer, ie ‘11892542’ or ‘11892542.0’. Do not include units, other text or the quote marks. Do not use exponential formats such as : ‘1.1892542e+06’. Do not use commas in the number such as ‘11,892,542’
7	area_observed	Drainage Region Area Observed by your satellite dataset (in square kilometres). This is area of the region chosen in column 5 that is actually observed and may be less than the full area in column 6.	A numerical value in units of Km2. Float or Integer, ie ‘11892542’ or ‘11892542.0’. Do not include units, other text or the quote marks. Do not use exponential formats such as : 1.1892542e+06.Do not use commas in the number such as ‘11,892,542’
8	start_date	Start date for this row’s interval in your mass trend time series (in decimal years).	A numerical value in units of years in the format ‘YYYY.yy’. Float, ie ‘1991.23’ or ‘2023.96’. Do not include units, other text or the quote marks.
9	end_date	End date for this row’s interval in your mass trend time series (in decimal years).	A numerical value in units of years in the format ‘YYYY.yy’. Float, ie ‘1991.23’ or ‘2023.96’. Do not include units, other text or the quote marks.
10	mass_rate	the Rate of Mass Change for each interval in your mass trend time series (in gigatons per year),.	A numerical value in units of gigatons per year. Float, ie ‘-100.45’ or ‘303.76’ Do not include units, other text or the quote marks. Do not include the ‘+’ character.
11	mass_rate_uncert	the Rate of Mass Uncertainty for each entry in your mass trend time series (in gigatons per year).	A numerical value in units of gigatons per year. Float, ie ‘-100.45’ or ‘303.76’ Do not include units, other text or the quote marks. Do not include the ‘+’ character.