Mass Balance Intercomparison

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IMBIE Mass Balance Intercomparison

This page describes the experimental protocol for the IMBIE Mass Balance inter-comparison for the IMBIE 2023 assessment. 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.
  • We currently cannot accept mass balance solutions derived from the combination of several techniques.
  • You are only allowed to submit one data set 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. In previous IMBIE submissions there was quite a wide interpretation of the submitted file formats by participants, often including format or value errors, which required a large effort by the IMBIE team to manually check and correct many of the submissions. In IMBIE-3 we hope to avoid this by performing stricter initial checks, 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 calculate the 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 the time-series over 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 every Zwally Antarctic basins ‘1’ to ’27’, also provide a time-series (multiple rows) for regions ‘AIS’, and optionally ‘EAIS’,’WAIS’,’APIS’. If you provide all Zwally or Rignot Greenland basins also provide a time-series for region ‘GRIS’. The description of the drainage basins can be found here.

 

General CSV File Requirements

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

  1. CSV format file names must end in .csv (we do not accept any other end strings such as .txt).
  2. CSV files should use UTF-8 character encoding (this is normally the default used by most modern programming languages).
  3. 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.
  4. CSV format files must contain comma separated values or strings. (ie String,Value,Value,…). No other delimiters are allowed.
  5. 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.
  6. Comment lines are allowed anywhere in the file. These lines must start with a # character as the first character. We ignore these lines.
  7. CSV files must not contain additional columns. The number of columns and the column order must exactly match the specification below.
  8. You must not include commas or any special characters (*/\'”_+) in your values or strings unless explicitly allowed below.
  9. Positive numerical values should not include the + sign.
  10. Floating point numbers should be represented by standard (not exponential) numbering. ie 123456.0 and not 1.234560+e05
  11. Do not include any commas in numerical values. ie use 10000 and not 10,000.
  12. Empty column entries are not allowed unless explicitly specified in the format description.
  13. Do not include NaN values.

 

  1. 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 can not 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 basin_type Drainage Region Set employed (Zwally or Rignot) A string containing one of ‘Zwally’, or ‘Rignot’. Do not include the quote marks. Case sensitive.
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.
Zwally Antarctic basin numbers:
‘1’, ‘2’, ‘3’, ‘4’, ‘5’, ‘6’, ‘7’, ‘8’, ‘9’, ’10’, ’11’, ’12’, ’13’, ’14’, ’15’, ’16’, ’17’, ’18’, ’19’, ’20’, ’21’, ’22’, ’23’, ’24’, ’25’, ’26’, ’27’, or
Zwally Antarctic regions:
‘AIS’, ‘EAIS’, ‘WAIS’, ‘APIS’, or
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
Zwally Greenland basins or regions:
‘1.1’, ‘1.2’, ‘1.3’, ‘1.4’, ‘2.1’, ‘2.2’, ‘3.1’, ‘3.2’, ‘3.3’, ‘4.1’, ‘4.2’, ‘4.3’, ‘5.0’, ‘6.1’, ‘6.2’, ‘7.1’, ‘7.2’, ‘8.1’, ‘8.2’, or
Zwally Greenland regions :
‘1’, ‘2’, ‘3’, ‘4’, ‘5’, ‘6’, ‘7’, ‘8’ (now allowed in IMBIE-3),or
Zwally Greenland regions :
‘GRIS’, or
Rignot Greenland regions:
‘NO’, ‘NE’, ‘SE’, ‘SW’, ‘CW’, ‘NW’, or
Rignot 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.
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 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, ie ‘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, ie ‘-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, ie ‘-100.45’ or ‘303.76’ Do not include units, other text or the quote marks. Do not include the ‘+’ character.

 

  1. 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 annual epochs or finer temporal duration. If you submit annual rates of mass change, please provide rates calculated over calendar years (from 1st January to 31st 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 can not 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 basin_type Drainage Region Set employed (Zwally or Rignot) A string containing one of ‘Zwally’, or ‘Rignot’. Do not include the quote marks. Case sensitive.
5 region_id Drainage Region ID A single string containing one of the strings shown below within the quote marks:
Zwally Antarctic basin numbers:
‘1’, ‘2’, ‘3’, ‘4’, ‘5’, ‘6’, ‘7’, ‘8’, ‘9’, ’10’, ’11’, ’12’, ’13’, ’14’, ’15’, ’16’, ’17’, ’18’, ’19’, ’20’, ’21’, ’22’, ’23’, ’24’, ’25’, ’26’, ’27’, or
Zwally Antarctic regions:
‘AIS’, ‘EAIS’, ‘WAIS’, ‘APIS’, or
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
Zwally Greenland basins or regions:
‘1.1’, ‘1.2’, ‘1.3’, ‘1.4’, ‘2.1’, ‘2.2’, ‘3.1’, ‘3.2’, ‘3.3’, ‘4.1’, ‘4.2’, ‘4.3’, ‘5.0’, ‘6.1’, ‘6.2’, ‘7.1’, ‘7.2’, ‘8.1’, ‘8.2’, or
Zwally Greenland regions :
‘1’, ‘2’, ‘3’, ‘4’, ‘5’, ‘6’, ‘7’, ‘8’ (now allowed in IMBIE-4),or
Zwally Greenland regions :
‘GRIS’, or
Rignot Greenland regions:
‘NO’, ‘NE’, ‘SE’, ‘SW’, ‘CW’, ‘NW’, or
Rignot 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.
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.

 

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