U.S. Department of the Interior

U.S. Geological Survey

Data Series 419

PRISM3/GISS Topographic Reconstruction
PRISM3/GISS Topographic Reconstruction

By Linda E. Sohl, Mark A. Chandler, Robert B. Schmunk, Ken Mankoff, Jeffrey A. 

Jonas, Kevin M. Foley, and Harry J. Dowsett

Prepared in cooperation with NASA Goddard Institute for Space Studies, and the 

Center for Climate Systems Research at Columbia University

Data Series 419

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2009

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Suggested citation:

Sohl, L.E., Chandler, M.A., Schmunk, R.B., Mankoff, Ken, Jonas, J.A., Foley, K.M., and Dowsett, H.J., 2009, PRISM3/

GISS topographic reconstruction: U.S. Geological Survey Data Series 419, 6 p.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Procedures......................................................................................................................................................1

Land Topography...................................................................................................................................1

Ice Sheet Distribution and Ice Topography......................................................................................2

Rationale..........................................................................................................................................................2

Tibetan Plateau......................................................................................................................................2

Andes Plateau .......................................................................................................................................2

Colorado Plateau/Rocky Mountains..................................................................................................3

Maps and Data...............................................................................................................................................3

Acknowledgments.........................................................................................................................................3

References Cited............................................................................................................................................3

Figures

1. Reconstructed PRISM3/GISS topography (GISS_P3_topo_v1.0).........................................5

2. Anomaly map showing the elevation changes made for the PRISM3/GISS topography 

with respect to the older PRISM2 topography.........................................................................6

Conversion Factors

Multiply By To obtain

Length

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

Abbreviations used in this report:

~ approximately

BAS British Antarctic Survey

BAS ISM British Antarctic Survey Ice Sheet Model

EAIS East Antarctic Ice Sheet

GCM General Circulation Model

GISS Goddard Institute for Space Studies

ISM Ice Sheet Model

NOAA National Oceanic and Atmospheric Administration

Ma Mega-annum

PNG Portable Network Graphics

PRISM Pliocene Research, Interpretation and Synoptic Mapping

RGB Red, Green, and Blue

SLR Sea Level Rise

USGS U.S. Geological Survey

Abstract

The PRISM3/GISS topographic reconstruction is one of 

the global data sets incorporated into a new reconstruction for 

the mid-Piacenzian warm interval of the Pliocene, at about 

3.3 to 3.0 Ma. The PRISM3/GISS topography-gridded data 

set is a digitization of a graphical reconstruction, provided at 

2° × 2° resolution and based on updated paleoaltimetry data 

and a refined land/ocean mask. Mid-Piacenzian topography 

as shown in this data set is generally quite similar to modern 

topography, with three notable differences: (1) the coastline 

as shown is 25 meters higher than modern sea level, reflecting 

the hypothesized reduction in ice sheet volume; (2) Hudson 

Bay is filled in to low elevation, in the absence of evidence 

for submergence at that time; and (3) the West Antarctic ice 

sheet is absent, permitting open seaways to exist in Ellsworth 

and Marie Byrd Lands. Two alternate ice sheet configurations 

with corresponding vegetation schemes are available; one is a 

minor modification of the PRISM2 ice reconstruction, and one 

is derived from the British Antarctic Survey Ice Sheet Model 

(BAS ISM).

Introduction

The PRISM3/GISS topographic reconstruction is a threedimensional global data set representing a best estimation of 

land and ice sheet relief for use with climate model simulations of the mid-Piacenzian. This time interval (~3.3–3.0 Ma, 

or “PRISM interval”) has been intensely studied as part of the 

U.S. Geological Survey Pliocene Research, Interpretation and 

Synoptic Mapping (PRISM) Project (Dowsett, 2007). This 

reconstruction was created at the NASA Goddard Institute for 

Space Studies (GISS) and builds upon the U.S. Geological 

Survey’s previous PRISM2 topography through the incorporation of recent paleoaltimetry data and information derived 

PRISM3/GISS Topographic Reconstruction

Linda E. Sohl,1 2 Mark A. Chandler,1 2 Robert B. Schmunk,2 Ken Mankoff,1 2 Jeffrey A. Jonas,1 2 Kevin M. Foley,3 

and Harry J. Dowsett3

from Markwick’s (2007) Pliocene paleogeography. A variant 

of the PRISM3/GISS topography that incorporates an alternate ice sheet and ice topography reconstruction created by 

the British Antarctic Survey (Hill and others, 2007) is also 

available.

Procedures

Land Topography

The previous PRISM1/PRISM2 digital topographic 

reconstruction for the PRISM interval (Dowsett and others, 

1994; Thompson and Fleming, 1996), at 2° × 2° grid resolution, was projected as an equirectangular (equidistant cylindrical) map image, and elevation contours were interpolated 

for greater ease in further modification. Markwick (2007), as 

a much more recent reconstruction of Pliocene topography, 

was generally used as reference for locations where the older 

PRISM1/PRISM2 map lacked detail at lower elevation ranges 

(for example, 0–500 meters), and the additional elevation 

information was drawn in accordingly. Where the PRISM 

topography supplied additional detail at low elevation, this 

information was retained and combined with Markwick’s data 

to produce smooth and geologically/geographically consistent 

elevation changes. Several map reconstructions were then produced, including a version that extrapolates topographic relief 

to the modern coastlines in order to permit the widest possible 

use among climate modeling groups with varying ability to 

modify ocean-continent distribution. In all cases the Hudson 

Bay region has been raised above sea level, assuming groups 

can mask that region if they are truly restricted to modern 

coastlines for experiments.

The maps were digitized using the G.Sampler software 

program developed at NASA, which analyzes the RGB color 

values of each pixel, binning the values based on a predefined 

latitude x longitude grid overlay. Each RGB combination (pixel) is then assigned a height above sea level, and a 

weighted average for each grid cell is generated. It should be 

noted that the northernmost and southernmost rows (first and 

last row of each array) should be averaged for input into general circulation models (GCMs) that use a single pole-centered 

cell over the North and South poles.

1

Center for Climate Systems Research at Columbia University, New York, 

NY.

2

NASA Goddard Institute for Space Studies, New York, NY.

3

U.S. Geological Survey, Reston, VA.
2 PRISM3/GISS Topographic Reconstruction

Ice Sheet Distribution and Ice Topography

As with the PRISM2 reconstruction, the topography of 

ice sheets in Greenland and Antarctica is included with land 

topography. Two ice sheet distributions are provided: one is 

a minor modification of the original PRISM2 ice, here called 

PRISM2 ́, and the other was produced by the British Antarctic 

Survey Ice Sheet Model (BAS ISM) (see below). Areas of ice 

sheet distribution are distinguishable in the associated vegetation reconstructions, where ice is assigned as a vegetation type 

(for example, Salzmann and others, 2008).

PRISM2’: This distribution is very similar to the older 

PRISM2 ice, with minor changes introduced in order to tie ice 

sheet distribution in Greenland more closely with the topographic reconstruction, as well as to produce a more “natural” 

outline for Antarctic ice. The size and shape of the Greenland 

ice sheet are reduced approximately 50 percent from its modern extent (Dowsett and others, 1994; Thompson and Fleming, 

1996) in order to supply approximately 4 m of the required 

25-m sea level rise. In Antarctica, the entire West Antarctic ice 

sheet has been removed to yield another 6 m of sea level rise. 

An independent ice sheet model (Michael Prentice, University 

of New Hampshire, personal commun., 1999, cited in Dowsett 

and others, 1999) was used to produce a smaller, more realistic East Antarctic ice sheet distribution that accommodated 

the remaining 15 m of sea level rise needed for the PRISM 

interval.

BAS ISM: This ice sheet distribution was created by the 

British Antarctic Survey Ice Sheet Model, a dynamic ice sheet 

model run asynchronously with the Hadley Centre’s HadAM3 

GCM (Hill and others, 2007). A “standard mid-Pliocene climate” experiment was run with the HadAM3, and the output 

of that run downscaled to a 50-km x 50-km grid for use in an 

array of sensitivity experiments conducted with the ISM. The 

East Antarctic Ice Sheet (EAIS) in the BAS reconstruction 

presented here represents the smallest of those ice reconstructions (Hill and others, 2007). In terms of area, the BAS ISM 

reconstruction is not significantly different from the PRISM2 ́, 

although the BAS ISM did yield slightly higher elevations 

across a wider area of the EAIS and portions of the Greenland 

ice sheet.

Rationale

As with the PRISM2 reconstruction, Pliocene sea levels 

are assumed to have been 25 m higher than present day (Dowsett and others, 1999). To create a coastline reflecting this 

change, we applied an ocean mask derived from ETOPO5 data 

(National Oceanic and Atmospheric Administration, 1988) 

over the modern continental outline, with some adjustments 

(fig. 1). In a departure from the PRISM2 land/ocean mask, 

Hudson Bay was filled in at low elevation, assuming that no 

part of it was yet submerged in Pliocene time. In Antarctica, 

the West Antarctic ice sheet is absent in this reconstruction, 

leaving open waterways in locations where the current bedrock elevation is less than 25 m above modern sea level.

Several terrestrial regions were of particular interest for 

this reconstruction, since at the time the PRISM1/PRISM2 

reconstruction was completed (Dowsett and others, 1994; 

Thompson and Fleming, 1996) insufficient data were available 

to provide good constraints on paleoaltimetry. These elevation 

differences are shown in figure 2.

Tibetan Plateau

Original PRISM2 topography: Elevations for the Tibetan 

Plateau itself were made roughly consistent with the modern 

day because of uncertainty over the timing of plateau uplift.

Current reconstruction: Elevations were left substantively unchanged, as more recent data suggest that the Tibetan 

Plateau has long been at or near current elevations. Oxygen 

isotope data from paleosol carbonates in Tibet imply an elevation of 5,200 m since the late Miocene (~10 Ma; Garzione, 

Dettman, and others, 2000; Garzione, Quade, and others, 

2000; Rowley and others, 2001) with no recognizable change 

in height of the High Himalaya since 20 Ma (Rowley and Garzione, 2007). Similar data from the southern Tibetan Plateau 

(Rowley and Garzione, 2007), in addition to paleoelevation 

data derived from Late Miocene (15.1 Ma) flora buried in 

ash (Spicer and others, 2003) suggest an elevation of 4,650 

to 5,200 m by ~15 Ma. The central Tibetan Plateau appears 

to have maintained a fairly consistent elevation in excess of 

4,000 m for the past ~35 million years (Rowley and Currie, 

2006), while isotope data from lake carbonates in the northern 

portion suggest that this area underwent significant uplift from 

less than 2,000 m to its current elevation of 4,700 m over the 

past 39 million years (Rowley and Garzione, 2007), although 

it is likely that the northern plateau had reached something 

akin to modern elevations by the PRISM interval. Portions of 

Central Asia beyond the Tibetan Plateau also appear to have 

achieved a modestly higher elevation than previously thought 

by this time, and so are shown at elevations some 500 m 

higher in the current reconstruction.

Andes Plateau

Original PRISM2 topography: Thompson and Fleming (1996) reduced the elevation of the western cordillera 

in northern South America to ~2,000 m, approximately half 

the modern value, in accordance with available geologic and 

isotopic studies.

Current reconstruction: Data from multiple isotopic 

paleoelevation proxies suggest that the central Andes had 

reached most of their current height (3,600–3,800 m) by 6.8 

Ma (Ghosh and others, 2006; Garzione and others, 2006; 

Rowley and Garzione, 2007), so only minor adjustments were 

needed showing an additional 500 m elevation along parts of 

the inner edge of the Peru salient/Chile recess. The northern-
PRISM3/GISS Topographic Reconstruction 3

most cordillera was left at elevations a few hundred meters 

lower than modern, as per Markwick (2007).

Colorado Plateau/Rocky Mountains

Original PRISM1/PRISM2 topography: Applying data 

from geologic and isotopic studies available at the time, 

Thompson and Fleming (1996) decreased the elevation of the 

western cordillera in North America elevations by half, to a 

maximum of approximately 1,500 m.

Current reconstruction: A reconstruction of a datum surface used to measure the amount of incision in the Colorado 

Plateau in the Late Cenozoic (McMillan and others, 2006) 

suggests that there has not been more than a 750-m increase in 

elevation since ~35 Ma. Modeling of the viscous mantle flow 

beneath the Colorado Plateau suggests that post-Laramide 

uplift of this region has been on the order of 1,200 m, much 

of it occurring within the past 10 million years (Moucha and 

others, 2008). Markwick (2007) thus gives this region nearmodern topographic relief, which we adopt for this reconstruction; it is roughly 1,500 to 2,000 m higher than the PRISM2 

topography.

Maps and Data

Multiple versions of the PRISM3/GISS topography 

are available as both map images and in digitized form. The 

map images are available in PNG format as supplementary 

material. Digitized versions of the data are available on the 

PRISM3 Web site (http://geology.er.usgs.gov/eespteam/prism/) 

at 2° x 2° (latitude x longitude) resolution and are available 

in two formats: (1) Microsoft® Excel, and (2) as netCDF files. 

Filenames and descriptions of the data they contain are below.

• GISS_P3_topo_v1.0: Values are given in meters above 

sea level and this data set incorporates a 25-m sea 

level rise (SLR) above modern based on ETOPO5 data 

(National Oceanic and Atmospheric Administration, 

1988). The coastline was also modified so that Hudson 

Bay is above sea level, as are the Great Lakes. The 

West Antarctic Ice Sheet was removed and shallow 

seas are present across much of the continent in that 

region.

• GISS_P2_ice_sheet_v1.0: This data set contains the 

fractional amount of ice sheet covering each grid cell. 

Values are given as a fraction of 1.0, with 1.0 representing 100 percent ice sheet cover and 0 percent 

representing no ice sheet cover.

• BAS_GISS_P3_topo_v1.1: Similar to GISS_P3_topo_

v1.0, except that the topography for Greenland and 

Antarctica uses ice sheets simulated by the BAS Ice 

Sheet Model.

• BAS_GISS_P3_ice_sheet_v1.1: Fractional coverage 

of the ice sheet distribution simulated by the BAS Ice 

Sheet Model. Values are given as a fraction of 1.0, 

with 1.0 representing 100 percent ice sheet cover and 0 

percent representing no ice sheet cover.

• GISS_P3_topo_v1.2: Includes the same Pliocene 

topography as in GISS_P3_topo_v1.0 except that the 

topographic elevation data are extended to modern 

coastlines. This is for climate models that cannot easily 

alter land/sea distributions from modern defaults. As in 

GISS_P3_topo_v1.0, Hudson Bay and the Great Lakes 

are above sea level and shallow seas are present across 

West Antarctica.

• GISS_P3_topo_v1.3: Includes the same Pliocene 

topography as in GISS_P3_topo_v1.0 except the topographic relief is extended to modern coastlines. As in 

GISS_P3_topo_v1.0, Hudson Bay and the Great Lakes 

are above sea level. Unlike v1.2, there are no shallow 

seas across Antarctica. This is for climate models that 

cannot easily alter land/sea distributions from modern 

defaults.

Acknowledgments

The authors thank P.J. Markwick for sharing his paleotopographic data, and D.B. Rowley for additional information. 

This work was supported by the USGS Earth Surface Dynamics Program and National Science Foundation Paleoclimate 

program grant ATM 0323516.

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and causes of post-Laramide relief in the Rocky Mountain 

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PRISM3/GISS Topographic Reconstruction 5Figure 1. Reconstructed PRISM3/GISS topography (GISS_P3_topo_v1.0).
6 PRISM3/GISS Topographic Reconstruction

Figure 2. Anomaly map showing the elevation changes made for the PRISM3/GISS topography with respect to the older PRISM2 topography.