Global Gridded Pliocene and Late Quaternary Sea Level
U.S. Geological Survey Open-File Report 96-000
by Peter N. Schweitzer and Robert S. Thompson
Image depicting the largest changes in global eustatic sea level that
have been inferred from geological studies. The light blue color shows
an estimate of the coastline of the eastern United States during the
last glacial maximum, about 20,000 years ago. The dark green shows the
modern coastline, and the lighter shades of green show the coastlines
that may have existed during the warm climatic interval of the middle
Pliocene epoch, about 3 million years ago.
This information is in preliminary release from USGS for purposes of
testing by general users. It should not (yet) be cited in official
scientific communications. Formal metadata (documentation) is available
in <URL:http://geochange.er.usgs.gov/pub/data/sea_level/Contents/FGDCmeta>.
Contents
Introduction
This report is a collection of digital information about major changes
in global sea level that occurred in the past at times when Earth's
climate was significantly different than it is today. Its objective
is to provide data on global land distribution and sea level for use
with general circulation models. These data are assembled using digital
data previously published by others, modified for these purposes via
simple algorithms. Results are expressed in formats suitable for use
in spreadsheet and image-processing applications.
Formal metadata
provide more complete documentation for these data. Metadata elements
describing the specific products are listed after the overall metadata
below. These partial metadata records are intended to supplement the
main record to provide complete documentation of the products.
Data sources
ETOPO5 by Margaret Edwards
- ETOPO5 was generated from a digital data base of land and sea- floor
elevations on a 5-minute latitude/longitude grid. The resolution of
the gridded data varies from true 5-minute for the ocean floors, the
U.S.A., Europe, Japan,and Australia to 1 degree in data-deficient
parts of Asia, South America, northern Canada, and Africa.
Data sources are as follows:
- Ocean Areas
- U.S. Naval Oceanographic Office
- USA, Western Europe, Japan, Korea
- U.S. Defense Mapping Agency
- Australia
- Bureau of Mineral Resources, Australia
- New Zealand
- Department of Industrial and Scientific Research, New Zealand
- Balance of world land masses
- U. S. Navy Fleet Numerical Oceanographic Center
These various data bases were originally assembled in 1988 into the
worldwide 5-minute grid by Margo Edwards, then at Washington
University, St. Louis, MO. ETOPO5 has a number of important limitations
including a pervasive offset in the registration of land pixels.
- TerrainBase by the National Geophysical Data Center
- The TerrainBase global digital terrain model contains a complete
matrix of land elevation and ocean depth values for the entire world
gridded at 5-minute intervals. NGDC/WDC-A developed the model using
the best public domain data available at the time of publication.
The version of TerrainBase available at this writing is release 1.0,
described by NGDC as a beta version, dated January 1994.
This beta version has a few significant errors in the vicinity of
Halifax, Nova Scotia, which we corrected before using TerrainBase
in this study.
- ICE4G by Professor W.R. Peltier
- These data describe global topography and ice distribution for each
1000-year interval from 21ka to the present. The data were generated
using a complex geophysical model that accounts for crustal ice loading
and rebound as well as eustatic sea-level rise.
Data products
Present
- Tables showing global distribution of land at 1-degree cell size, 360 columns, 180 rows, tab-delimited ASCII
- Images depicting present-day global topography
- Grid-cell size of 5 arc-minutes (4320x2160 pixels)
- Grid-cell size of 20 arc-minutes (1080x540 pixels)
- Key to colors showing what depth ranges they represent,
GIF or
PICT
Late Quaternary
- Tables showing global distribution of land at 1-degree cell size, 360 columns, 180 rows, tab-delimited ASCII (based on grid of 5-minute cell size), one per thousand years from 0 to 21 ka, inclusive, tab-delimited ASCII
- Images depicting global topography and ice thickness at 1-degree cell size, 360 columns, 180 rows
- One per thousand years before present, as
- Animations depicting global topography and ice thickness at 1-degree cell size, 360 columns, 180 rows, with 22 time intervals
Pliocene
- Tables showing global distribution of land at 1-degree cell size, 360 columns, 180 rows, tab-delimited ASCII (based on grid of 5-minute cell size), one each for higher-than-modern eustatic sea-levels of 10,20,25,30,35,40,45,50, and 60 meters
- Images depicting expected global coastlines with eustatic sea-level of -120, 0, 35, and 60 meters from present, not accounting for ice loading)
- Grid-cell size of 5 arc-minutes (4320x2160 pixels)
- Grid-cell size of 20 arc-minutes (1080x540 pixels)
- Key to colors showing what depth ranges they represent,
GIF or
PICT
Software
Most of the software used to create these data products is original.
Because studying the software and the manner in which it was
used may help users understand the procedures, the software and
makefiles are listed below. The makefiles are written for use under
UNIX with the make utility. In addition to these programs,
we used several image-format conversion utilities from the NetPBM
version of the PBMplus package, originally written by Jeff Poskanzer.
- Programs
- color_topo.c
- Creates a portable pixmap depicting elevation and bathymetry from a 4320x2160 16-bit image such as ETOPO5 or TerrainBase
- color_ice4g.c
- Creates a portable pixmap depicting topography and ice cover from one of W.R. Peltier's top.nn files and the corresponding file is_ice.nn.
- key.c
- Creates a key relating colors to depth ranges for color_topo.c. Requires X11R4 or later.
- subtract.c
- Subtracts one 4320x2160 16-bit image from another.
- bilinear.c
- Expands a 360x180 16-bit image to 4320x2160 using bilinear interpolation.
- add_topo.c
- Adds one 4320x2160 16-bit image to another.
- q1x1.c
- Read a 4320x2160 16-bit image containing elevation and bathymetry data and from it calculates a 1-degree grid containing percent land cover.
- subset_topo.c
- From a 4320x2160 16-bit image, creates a subset 16-bit image, adds a constant to all of the pixels in the subset, or both.
- Makefiles
- Modern
- Late Quaternary
- Pliocene
Contacts
Peter Schweitzer
Mail Stop 906, National Center
12201 Sunrise Valley Drive
Reston, VA 20192
Tel: (703) 648-6533
FAX: (703) 648-6647
email: pschweitzer@usgs.gov
Robert S. Thompson
Box 25046, Mail Stop 919
Denver Federal Center
Denver, CO 80225-0046
Tel: 303-236-5347
Fax: 303-236-5349
email: rthompson@usgs.gov
This page is currently <URL:http://geochange.er.usgs.gov/pub/data/sea_level/ofr96000.html> and WILL be renamed.
Maintained by Peter Schweitzer
Last updated 7-Nov-1996
