Ocean Basin and Lake Polygons for Sea Level Grids

This collection of files contains geographically registered polygons defining the shape of ocean basins and large lakes across the globe, designed for use in gridding and analysis of satellite-based observations of sea level.  In particular, this data set was produced as part of the NASA-SSH (https://podaac.jpl.nasa.gov/NASA-SSH) effort, whose aim is to deliver continuously updated, climate-quality, global observations of sea level derived from radar altimeter observations. 

The polygons were derived using products from free vector and raster map data Natural Earth (https://naturalearthdata.com).  Ocean basins were derived from version 5.1.0 of the 1:10m Marine Areas:

https://www.naturalearthdata.com/downloads/10m-physical-vectors/

and Lakes were derived from version 5.0.0 of the 1:50m Lakes and Rivers polygons:

https://www.naturalearthdata.com/downloads/50m-physical-vectors/

For the lakes, only the largest 26 lakes and inland seas were retained, as most smaller lakes are not typically sampled by traditional nadir altimeters.  For the marine basins, some polygons were joined or sometimes split in order to simplify grouping altimeter data by regions where it is expected to be geographically correlated.  For example, southern sections were split from the South Pacific and South Atlantic Oceans to simplify separation of these basins across the South American Peninsula. 

In addition to the polygons themselves, a table listing connections between polygons is also provided.  This allows users to select observations in regions that are likely to be correlated over time scales of days to weeks or longer. Each polygon carries a unique numerical identifier (the Arctic Ocean is 1, the Southern Ocean is 2, etc…).  For each identifier, the connection table lists all of the other identifiers that polygon is connected to.  This is used in the NASA-SSH gridding process to down-select data used to estimate sea level at a specific location.

Both the ocean and lake polygons themselves, and the connection table can be easily visualized in Google Earth (or other geographic mapping software) using the KMZ file provided.   The connection table provides sets of polygons connected to each individual feature.  For example, the Arctic Ocean polygon is connected to the Beaufort Sea, the Greenland Sea, the Barents Sea, etc.  These can be easily visualized by turning on subsets of features in the Basin Connections folder within the KMZ file.

Files contained in this dataset include:

basin_files.tar.gz – a tar gzip file that contains a .dbf, .prj, .shx, and .shp Shape file that can be loaded into a geographic mapping program such as QGIS or Google Earth.  This contains the polygon definitions, including their names.

basin_name_table.txt – an ascii text file containing a list of all the basin ID numbers and simplified version of the basin names, separated by a colon “:”.  A few basins were created for this dataset and do not have common geographic names.  These are given names based on their ID number for example “Feature ID: 240”. 

basin_connection_table.txt – an ascii text file containing a list of all the basin ID numbers that are geographically connected to a given basin ID.  The basin ID number in question is listed first on each row, and the connected ID numbers follow a colon “:”, in a comma separated list.

NASA-SSH Basins.kmz – This KMZ file contains all of the polygon definitions, along with the set of polygons for each basin that shows which basins it is connected to.  If loaded into Google Earth, it will create a folder in the Google Earth “Places” panel called “NASA-SSH Basins”.  Below this, two subfolders will be created, one will be called “All Basin Polygons” and will contain all of the basins polygons colored red.  Clicking on any one of the polygons will show the Basin ID number and name of this polygon.  The second subfolder is called “Basin Connections” and contains a list of subfolders, one for each Basin ID.  These can be turned on 1 at a time and will show a given basin polygon and all of the polygons it is connected to.

If you use these data please cite:

Willis, J.K., J. Sanchez, R. Santos, and S. Fournier,  Ocean Basin and Lake Polygons for Sea Level Grids, at DOI:10.5281/zenodo.13910542.