Data Set ID:
NSIDC-0192

Sea Ice Trends and Climatologies from SMMR and SSM/I-SSMIS, Version 3

NSIDC provides this data set to aid investigations of variability and trends in sea ice cover. Ice cover in these data are indicated by sea ice concentration: the percentage of the ocean surface covered by ice. The ice-covered area indicates how much ice is present; it is the total surface area of a pixel multiplied by the ice concentration in that pixel. Ice persistence is the percentage of months over the data set time period that ice existed at a location. The ice extent indicates whether ice is present; here, ice is considered to exist in a pixel if the sea ice concentration exceeds 15 percent. This data set provides users with data about total ice-covered areas, sea ice extent, ice persistence, and monthly climatologies of sea ice concentrations.

Version Summary:

Changes to this version include: 

  • Incorporated a change from Version 2 to Version 3 of the Bootstrap data set. For V3 Bootstrap data, the concentration record was re-calculated for the entire period of the data set, 1978 through current processing. The most impactful changes were a lowering of the threshold to 10% for ice extent, and the recalculation of the algorithm’s tie points every day. However, despite the new 10% threshold for Bootstrap input data, this Sea Ice Trends and Climatologies data set continues to be derived using a 15% threshold.

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Sea Ice Trends and Climatologies from SMMR and SSM/I-SSMIS, Version 3

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Geographic Coverage

Parameter(s):
  • Sea Ice > Ice Extent
  • Sea Ice > Sea Ice Concentration
Spatial Coverage:
  • N: -39.23, S: -90, E: 180, W: -180

  • N: 90, S: 30.98, E: 180, W: -180

Spatial Resolution:
  • 25 km x 25 km
Temporal Coverage:
  • 26 October 1978 to 31 December 2016
Temporal Resolution: Varies
Data Format(s):
  • ASCII Text
  • JPEG
  • PNG
  • Binary
Platform(s) DMSP 5D-2/F11, DMSP 5D-2/F13, DMSP 5D-2/F15, DMSP 5D-2/F8, DMSP 5D-3/F17, Nimbus-5, Nimbus-7
Sensor(s): ESMR, SMMR, SSM/I, SSMIS
Version: V3
Data Contributor(s): Julienne Stroeve, Walt Meier

Data Citation

As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.

Stroeve, J. and W. Meier. 2018. Sea Ice Trends and Climatologies from SMMR and SSM/I-SSMIS, Version 3. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: https://doi.org/10.5067/IJ0T7HFHB9Y6. [Date Accessed].

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Detailed Data Description

NSIDC provides this data set to aid investigations of variability and trends in sea ice cover. Ice cover in these data are indicated by sea ice concentration: the percentage of the ocean surface covered by ice. The ice-covered area indicates how much ice is present; it is the total surface area of a pixel multiplied by the ice concentration in that pixel. Ice persistence is the percentage of months over the data set time period that ice existed at a location. The ice extent indicates whether ice is present; here, ice is considered to exist in a pixel if the sea ice concentration exceeds 15 percent. This data set provides users with data about total ice-covered areas, sea ice extent, ice persistence, and monthly climatologies of sea ice concentrations.

Total Ice-Covered Areas and Sea Ice Extent Data

Along with one historical data file from the Electrically Scanning Microwave Radiometer (ESMR), these data are derived from the Scanning Multichannel Microwave Radiometer (SMMR), the Special Sensor Microwave/Imager (SSM/I), and the Special Sensor Microwave Imager/Sounder (SSMIS).

Daily and Monthly Total Ice-Covered Area and Total Sea Ice Extent Data

Daily Arctic and Antarctic ice-covered area and total sea ice extent ASCII text data files list the total ice-covered area (km2) and total sea ice extent (km2) for both the Bootstrap Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS and/or the NASA Team Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS Passive Microwave Data algorithms.

Monthly mean sea ice concentrations were used to derive monthly extents for both the NASA Team and Bootstrap algorithms. 

Regional Graphs: Time-Series Plots

The total ice-covered area and sea ice extent data are used to create .png images of regional monthly time-series plots of ice-covered areas, area anomalies, ice extent, and extent anomalies for both the NASA Team and Bootstrap algorithms. The scientific basis for these algorithms and their validation are discussed in Parkinson and Cavalieri (2012), Cavalieri and Parkinson (2008), and Parkinson et al. (1999).

Ice Persistence

Monthly climatologies of ice persistence binary data files with corresponding .png images are intended for users interested in persistence of ice over a particular month during the time series, which includes January 1979 through current processing. Ice persistence fields provide information on how frequently ice occurs in a region during a given month over the time period of the data. The ice extent climatologies are derived each month from monthly-averaged sea ice concentrations using the NASA Team data.

Monthly Climatology of Sea Ice Concentration

Monthly sea ice concentration climatology binary data files with corresponding .png images represent mean ice concentration for each month over the entire time period of January 1979 through current processing. The data are derived from the NASA Team data.

Format

Data are provided in the following formats:

Total Ice-Covered Areas and Sea Ice Extent
ASCII text
PNG browse

Ice Persistence
Two-byte integer binary
PNG browse

Monthly Climatology of Sea Ice Concentration
Flat, one-byte integer binary
PNG browse

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File and Directory Structure

Data are available at: 

https://daacdata.apps.nsidc.org/pub/DATASETS/nsidc0192_seaice_trends_climo_v3/

This main directory contains three folders:

  • ice-persistence/ - Contains monthly climatologies of ice persistence binary data files and a browse/ folder with corresponding .png images of monthly ice persistence
  • monthly-climatology/ - Contains monthly sea ice concentration climatology binary data files and a browse/ folder with corresponding .png images of monthly climatologies
  • total-ice-area-extent/ - Contains three sub folders:
    • bootstrap/ - Contains ASCII text data files and a browse/ folder with .png files of regional graphs showing monthly time-series plots of ice-covered area, area anomalies, ice extent, and extent anomalies
    • esmr-smmr-ssmi-merged/ - Contains ASCII text data files of daily and monthly sea ice extent summaries from 01 January 1972 to 31 December 2002 for the Northern Hemisphere and 01 January 1973 to 31 December 2002 for the Southern Hemisphere
    • nasateam/ - Contains ASCII text data files and a browse/ folder with .png files of regional graphs showing monthly time-series plots of ice-covered area, area anomalies, ice extent, and extent anomalies

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File Naming Conventions

Files are named according to the following conventions:

Ice Persistence

Convention: persistence.mmm.1979-yyyy.h
Example: persistence.apr.1979-2015.n

where: 

Table 1. File Naming Convention for Ice Persistence Data Files
Variable Description
persistence Identifies this as an ice persistence data file
mmm 3-character month abbreviation
1979 First year for which data are available
yyyy 4-digit year of the last year for which data are available
h Hemisphere (n: Northern, s: Southern)


Monthly Climatology of Sea Ice Concentration

Convention: mean.mmm.1979-yyyy.h
Example: mean.apr.1979-2015.n

where:

Table 2. File Naming Convention for Monthly Climatology of Sea Ice Concentration Data Files
Variable Description
mean Identifies this as a mean ice concentration percentage data file
mmm 3-digit month abbreviation
1979 First year for which data are available
yyyy 4-digit year of the last year for which data are available
h Hemisphere (n: Northern, s: Southern)


Total Ice Area Extent

Bootstrap and NASA Team Files

The following file naming conventions pertain to both the NASA Team and Bootstrap algorithm data files. Data are provided in two different temporal resolutions: daily and monthly.

There are two different types of daily files: ice covered area files and sea ice extent files.

There are six different types of monthly files: ice covered area files, sea ice extent files, ice covered area anomaly files, sea ice extent anomaly files, monthly mean ice covered area files, and monthly mean sea ice extent files.

Monthly anomalies of ice-covered area and ice extent are calculated from monthly mean ice concentrations throughout the period of study. These anomalies show the deviations from the mean monthly values averaged over the entire time series.

Conventions: 
gsfc.algorithm.xxxx.area.1978-yyyy.h
gsfc.algorithm.xxxx.extent.1978-yyyy.h
gsfc.algorithm.xxxx.anomaly.area.1978-yyyy.h
gsfc.algorithm.xxxx.anomaly.extent.1978-yyyy.h

gsfc.algorithm.xxxx.mean.area.1978-yyyy.h
gsfc.algorithm.xxxx.mean.extent.1978-yyyy.h

where:

Table 3. File Naming Convention for Total Ice Area Extent Files
Variable Description
gsfc Indicates that data were acquired from Goddard Space Flight Center (GSFC)
algorithm Algorithm used to process the data (nasateam or bootstrap)
xxxx Indicates that this file is either daily or monthly
anomaly Indicates that this file contains the difference between the monthly data (area or extent) and the total monthly mean for the entire temporal coverage period
area Indicates that this file contains ice-covered area measurements
extent Indicates that this file contains sea ice extent measurements
1978 First year for which data are available
yyyy 4-digit year of the last year for which data were available
h Hemisphere (n: Northern, s: Southern)


ESMR-SMMR-SSM/I-SSMIS-Merged Sea Ice Extent

Data are provided in two different temporal resolutions: daily and monthly.

Conventions: 
gsfc.nasateam.extent.1972-yyyy.h
gsfc.nasateam.month.extent.1972-yyyy.h

Examples: 
gsfc.nasateam.extent.1972-2002.n
gsfc.nasateam.month.extent.1972-2002.n

where:

Table 4. File Naming Conventions for ESMR-SMMR-SSM/I-SSMIS-Merged Sea Ice Extent Files
Variable Description
gsfc.nasateam Indicates this is GSFC data processed with the NASA Team algorithm
extent Indicates this file contains sea ice extent measurements
month Indicates this file contains monthly averaged data (otherwise daily)
1972 First year for which data are available
yyyy 4-digit year (most recent year of processing)
h Hemisphere (n: Northern, s: Southern)
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Column Headers in ASCII Text Files

Total Ice Area and Extent

Data are in ASCII text format arranged in columns as described in Table 5.

Table 5. Column Header Descriptions for Total Ice Area and Extent ASCII Text Files
Column Description
Year 4-digit year
Mon 1-digit and 2-digit month
Day 1-digit and 2-digit day of month
DOY 3-digit day of year
Ver Version number of input NASA Team or Bootstrap data (pre: preliminary, v01: version 01, v02: version 02)
Region The remaining columns of the Arctic and Antarctic daily area and daily extent files list the total ice-covered area (km2) and total sea ice extent (km2), respectively. The columns are labeled by region. Refer to Table 6 and Table 7 for a list of abbreviations for column names.

The following tables list the Arctic and Antarctic regions covered by this data set and define the abbreviations in the data files.

Table 6. Arctic Regions and Abbreviations
Arctic Region Abbreviation
Total Arctic TotalArc
Seas of Okhotsk & Japan Okhotsk
Bering Sea Bering
Hudson Bay Hudson
Baffin Bay Baffin
Greenland Sea Grnland
Kara and Barents Seas BarKara
Arctic Ocean ArctOcn
Canadian Archipelago CanArch
Gulf of St. Lawrence StLawr
Table 7. Antarctic Regions and Abbreviations
Antarctic Region Abbreviation
Total Antarctic TotalAnt
Weddell Sea Weddell
Indian Ocean Indian
Pacific Ocean Pacific
Ross Sea Ross
Bellingshausen and Amundsen Seas BellAm


Merged ESMR-SMMR-SSMI Sea Ice Extent

Data are in ASCII text format arranged in columns as described in Table 8 and Table 9 for the daily and monthly data.

Column Number Description
Table 8. Column Descriptions for Merged Daily Data Files
1 4-digit year
2 1-digit and 2-digit month
3 1-digit and 2-digit day of month
4 1-digit to 3-digit day of year
5 Observed/interpolated sea ice extent (106 km2)
Column Description

Table 9. Column Descriptions for Merged Monthly Data Files
Year 4-digit year
Months (remaining 12 columns) 3-character month abbreviation
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File Size

File sizes vary, but generally are:

  • 136,192 bytes for Northern Hemisphere data files
  • 104,912 bytes for Southern Hemisphere data files
  • 25-40k bytes for .png browse images
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Spatial Coverage

N: -39.23, S: -90, E: 180, W: -180
N: 90, S: 30.98, E: 180, W: -180

Spatial Resolution

25 km x 25 km

Projections

Arctic: NSIDC Sea Ice Polar Stereographic North
Antarctic: NSIDC Sea Ice Polar Stereographic South

Grids

For the Northern Hemisphere, the grid size is 304 x 448 pixels.
For the Southern Hemisphere, the grid size is 316 x 332 pixels.

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Temporal Coverage

The temporal coverage for this data set is 26 October 1978 to 31 December 2016. 

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Parameters

Parameters include:

  • Sea Ice Concentration
  • Total Ice-Covered Area (km2)
  • Total Sea Ice Extent (km2)

Parameter Description

Ice Persistence

The ice persistence data indicate the historical frequency of the presence of ice with at least 15 percent concentration in each pixel of the 25 km polar stereographic grid in binary format.

Northern Hemisphere binary files are 304 x 448 bytes.
Southern Hemisphere binary files are 316 x 332 bytes.

Table 10 lists the data values for the ice persistence files.

Value Description
Table 10. Data Values for Ice Persistence Files
0 Water, no ice
1 - 100 Historical frequency of the presence of ice, as a percentage
253 Coastlines (land adjacent to water)
254 Land

Monthly Climatology of Sea Ice Concentration

The monthly climatology data give the average sea ice concentration for each polar stereographic pixel. A minimum concentration value of 15 percent is imposed. When concentrations are lower than this, the grid cell is considered to be free of ice.

Northern Hemisphere binary files are 304 x 448 bytes.
Southern Hemisphere binary files are 316 x 332 bytes.

Table 11 lists the data values for the ice persistence files.

Value Description
Table 11. Data Values for the Monthly Climatology of Sea Ice Concentration Files
0 Water, no ice
15 - 100 Average ice concentration; minimum concentration is 15 percent
251 Indicates pole hole; no direct satellite observation
253 Coast (land adjacent to water)
254 Land

Total Ice-Covered Areas and Sea Ice Extent

The daily and monthly total sea ice extent and sea ice area data for specified Arctic and Antarctic regions are displayed in ASCII text tables. Anomalies are also provided, which indicate departures from the long-term averages.

Sample Data Images

Total Ice-Covered Areas and Sea Ice Extent

Figures 1 and 2 show Bootstrap sample data images for the Total Ice-Covered Areas and Sea Ice Extent data files.

sample data of browse file
Figure 1. Total Ice-Covered Areas and Sea Ice Extent ASCII Text Bootstrap Sample Data File for the
Northern Hemisphere (gsfc.bootstrap.daily.area.1978-2015.n)
total-ice-coverd-area-gsfc-bootstrap-anomaly-area-arctic-ocean_1978-2015_n
Figure 2. Total Ice-Covered Areas and Sea Ice Extent PNG Bootstrap Sample Data File for the Northern Hemisphere (gsfc.bootstrap.anomaly.area.Arctic-Ocean.1978-2015.n.png)

Figures 3 and 4 show NASA Team sample data images for the Total Ice-Covered Areas and Sea Ice Extent data files.

Total Ice-Covered Areas and Sea Ice Extent ASCII Text NASATEAM Sample Data File
Figure 3. Total Ice-Covered Areas and Sea Ice Extent ASCII Text NASA Team Sample Data File for the Southern Hemisphere (gsfc.nasateam.daily.area.1978-2015.s)
Total Ice-Covered Areas and Sea Ice Extent PNG NASATEAM Sampe Data File
Figure 4. Total Ice-Covered Areas and Sea Ice Extent PNG NASA Team Sample Data File for the Southern Hemisphere (gsfc.nasateam.extent.Total-Antarctic.1978-2015.s.png)

Sea Ice Persistence

Figures 5 through 8 show sample data images of the Sea Ice Persistence data files for both the Northern Hemishphere and Southern Hemishphere.

Note:  The following sample data images (Figures 5 through 12) were created using a deprecated version of this data set which only included data through 2015. Therefore, these images are intended as visual examples only and should not be compared to the latest version, which includes data through 31 December 2016.

Coastal values in the binary files are outlined in red in the following figures. Browse images in .png format include a color bar indicating the scale used for the persistence frequency.
sea ice persistance image
Figure 5. Sea Ice Persistence Binary Sample Data File of the Southern Hemisphere (persistence.dec.1979-2015.s)
Figure 6. Sea Ice Persistence PNG Sample Data File of the Southern Hemisphere (persistence.dec.1979-2015.s.png)
sea ice persistence southern hemisphere binary files
Figure 7. Sea Ice Persistence Binary Sample Data File of the Northern Hemisphere (persistence.dec.1979-2015.n)
ice persistence png image
Figure 8. Sea Ice Persistence PNG Sample Data File of the Northern Hemisphere (persistence.dec.1979-2015.n.png)

Monthly Climatology of Sea Ice Concentration

Figures 9 through 12 show sample data images of the Monthly Climatology of Sea Ice Concentration data files for both the Northern Hemishphere and Southern Hemishphere.

Monthly Climatology of Sea Ice Concentration Binary Sample Data File of the Northern Hemisphere
Figure 9. Monthly Climatology of Sea Ice Concentration Binary Sample Data File of the Northern Hemisphere (mean.dec.1979-2015.n)
Monthly Climatology of Sea Ice Concentration PNG Sample Data File of the Northern Hemisphere
Figure 10. Monthly Climatology of Sea Ice Concentration PNG Sample Data File of the Northern Hemisphere
(mean.dec.1979-2015.n.png)
Monthly Climatology of Sea Ice Concentration Binary Sample Data File of the Southern Hemisphere
Figure 11. Monthly Climatology of Sea Ice Concentration Binary Sample Data File of the Southern Hemisphere (mean.dec.1979-2015.s)
Monthly Climatology of Sea Ice Concentration PNG Sample Data File of the Southern Hemisphere
Figure 12. Monthly Climatology of Sea Ice Concentration PNG Sample Data File of the Southern Hemisphere
(mean.dec.1979-2015.s.png)
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Software and Tools

Regional Map Tool

To view time-series plots of an area, area anomalies, extent, and extent anomalies for each region, click on the colored region area in the maps in Figures 13 and 14.

To view graphs for an entire area, visit the Total Arctic or Total Antarctic pages.

Example
Figure 13. Arctic Region Areas
Figure 14. Antarctic Region Areas
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Data Acquisition and Processing

Derivation Techniques and Algorithms

Data Sources

These data are derived from the following sources: 

Processing Steps

Total Ice-Covered Areas and Sea Ice Extent

In computing the total ice-covered area and ice extent data with both the NASA Team and Bootstrap algorithms, pixels must have an ice concentration of 15 percent or greater to be included. Total ice-covered area is defined as the area of each pixel with at least 15 percent ice concentration multiplied by the ice fraction in the pixel (0.15 to 1.00). Total ice extent is computed by summing the number of pixels with at least 15 percent ice concentration multiplied by the area per pixel; thus, the entire area of any pixel with at least 15 percent ice concentration is considered to contribute to the total ice extent. Anomalies are the difference between the current time period's average value and the long-term average.  A positive anomaly indicates that the current period has greater extent or area than the average.

Ice Persistence

Individual ocean pixels containing a minimum of 15 percent ice cover are summed throughout the time series. The maximum ice persistence value is 100 percent. Each pixel represents the percentage of years for which ice was present during that month. Only the NASA Team algorithm is used to compute these data.

Monthly Climatology of Sea Ice Concentration

A threshold of 15 percent concentration is applied to the monthly climatology fields. Only the NASA Team algorithm is used to compute these data.

Missing Data and Monthly Anomalies

Periods for which there are no available data are described in Table 12.

Monthly anomalies of ice-covered area and ice extent are calculated from monthly mean ice concentrations throughout the period of study. These anomalies show the deviations from the mean monthly values averaged over the entire time series.

Table 12. Missing Data
Time Periods Data Type Description
October 1978, December 1987 Sea ice Sea ice data are missing for most days, so monthly values are not calculated for these months.
January 1988 Sea ice January 1988 is missing data for the first half of the month. A value is given for this month, but the value may not represent true monthly mean since the sea ice data are incomplete.

Gap in Coverage over the North Pole

There is a circular section over the Northern Hemisphere pole known as the pole hole, which is never measured due to orbit inclination. For the purposes of ice extent, pixels under the pole hole are always considered to be at least 15 percent. For total ice-covered area, the pixels under the pole hole are not used. The Southern Hemisphere also has a pole hole, but it does not affect this sea ice data set because there is only land under this hole. For SMMR, the hole is 611 km in radius and is located poleward of 84.5 degrees North. For SSM/I and SSMIS, the hole is 311 km in radius and is located poleward of 87.2 degrees North.

The difference in pole hole areas between SMMR and SSM/I-SSMIS results in a discontinuity in the Northern Hemisphere ice-covered area time series across the instrument transitions.
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Sensor or Instrument Description

For information regarding the sensors used for this product, refer to the SMMR, SSM/I, and SSMIS Sensors page.

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Version History

Table 13 provides a summary of the version history of this product. 

Version Date Implemented Description of Updates
Table 13. Summary of Version History
Version 3 06 April 2018

Changes to this version include: 

  • Incorporated a change from Version 2 to Version 3 of the Bootstrap data set. For V3 Bootstrap data, the concentration record was re-calculated for the entire period of the data set, 1978 through current processing. The most impactful changes were a lowering of the threshold to 10% for ice extent, and the recalculation of the algorithm’s tie points every day. However, despite the new 10% threshold for Bootstrap input data, this Sea Ice Trends and Climatologies data set continues to be derived using a 15% threshold.
Version 2 01 January 2017

Changes to this version include: 

Version 1 28 July 2014

No science changes were made during this update. 

04 September 2013
Changes included in this update are: 
2004 Initial release of this data product.

Version 3 Update Notice

01 March 2018

The climatology presents a summary of the long-term record of satellite-derived sea ice concentrations calculated using the NASA Team (NT) and Bootstrap (BT) algorithms. Prior to this update, the climatology included NT and BT data from 1978 through 2015. Because no changes were made to the NT data that were used in the previous version of this product, only small differences due to averaging data from an additional year are expected.

Findings

Because the ice persistence and monthly climatology fields are based on the NT data set, there are only small differences. A few grid cells have small changes, but overall there are minimal changes in the ice persistence and monthly climatology fields in both hemispheres for all months.

The NT-derived fields of regional ice extent and areas similarly consist of just the additional year of data; the values through the end of 2015 are unchanged.

The BT-derived fields do show widespread changes because the underlying Bootstrap data have been updated to a new version. While monthly hemisphere-wide areas show average area increases of less than 2%, some smaller regions—for which even small changes in ice area can be a large percentage of the region’s total—can show much larger percentage changes.

While monthly hemisphere-wide areas show average area increases of less than 2%, some smaller regions–for which even small changes in ice area can be a large percentage of the region’s total–can show much larger percentage changes.

Recommendations

The updated Sea Ice Trends and Climatologies data are consistent in format and value with the previous version and can be used for the same purposes. Because the Bootstrap data have been updated for the entire time series, users of the Bootstrap data should update those applications with the entire Bootstrap data set. 

Version 2 Update Notice

01 January 2017

In the Northern Hemisphere, very small differences in sea ice extent were found: less than 0.2 percent for the NASA Team algorithm and less than 0.05 percent for the Bootstrap algorithm.

Differences in Northern Hemisphere sea ice area were also small. Most years had less than 0.05 percent. Differences in the Bootstrap sea ice area were generally less than 0.01 percent.

For both the Bootstrap and NASA Team algorithms, the differences in the Southern Hemisphere were negligible.

These small differences are found in the persistence and monthly climatology data also. The Northern Hemisphere monthly fields showed no difference in 95-98 percent of the sea ice values, and fewer than 0.02 percent of pixels had differences in ice concentration of greater than 2 percent.

Version 1 Update Notice

28 July 2014

Data are now available through 31 December 2013 for all Sea Ice Trends and Sea Ice Trends and Climatologies from SMMR and SSM/I-SSMIS data sets.

Version 1 Update Notice

04 September 2013

Reprocessing is complete and updated data are now available through 31 December 2012 for all Sea Ice Trends and Sea Ice Trends and Climatologies from SMMR and SSM/I-SSMIS data sets. With this update, the following changes have been implemented:

Total Ice-Covered Area and Extent

The cutoff value which defines a region as ice-covered or not ice-covered has been adjusted from 14.8 percent to 15 percent to more closely match the methodology used to calculate other sea ice extent and area products at NSIDC.

Ice Persistence and Monthly Climatology of Sea Ice Concentration (Monthly Means)
  • Includes the new 15 percent cutoff value described above.
  • To prevent inconsistencies between different algorithms, these parameters are now calculated exclusively using the NASA Team algorithm.
Monthly Ocean Masks and Maximum Extent Masks

The ocean mask files and maximum extent mask files were removed as they are not the masks used in the production of these data sets.

This most recent reprocessing also rectifies two previous releases of these data sets that contained erroneous data. In January/February of 2012, and May of 2013, the products were to have contained data from 2007 to 2010 and from 2010 to 2011, respectively. However, the climatology products contained data only through 2007. We recommend replacing previously downloaded 2010 and 2011 climatology data files with the climatology files that now extend through 2012. The Total Ice-Covered Area and Extent data set did contain post-2007 data, but reprocessed data utilizing the new methodology are available in the 2012 release.

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References and Related Publications

Contacts and Acknowledgments

Julienne Stroeve
Polar Observation & Modelling
University College London

Walt Meier
National Snow and Ice Data Center 

Document Information

DOCUMENT CREATION DATE

January 2017

DOCUMENT REVISION DATE

April 2018

No technical references available for this data set.

FAQ

What is the difference between the NASA Team algorithm and the Bootstrap algorithm?
For general analyses or creation of simple images, either algorithm will suffice. The Bootstrap sea ice concentration data set is believed to be more useful for modeling and process studies in the polar regions because it is generally free of residual errors that could not be removed by... read more

How To

How to import the sea ice trends data into ArcGIS
The following are instructions describing how to import "Sea Ice Trends and Climatologies from SMMR and SSM/I-SSMIS" binary files into ArcGIS. These instructions were tested with ArcInfo 10.0. 1. Rename the Data File. In order to be able to import a Polar Stereographic monthly climatology sea... read more