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December 23, 1999

Lake Ontario

The National Oceanic and Atmospheric Administration released a color poster depicting new bathymetry of Lake Ontario. This poster represents the third Lake among the five Laurentian Great Lakes for which new, highly detailed bathymetry has been completed. It is the latest in a series of bathymetric map posters and data sets on CD-ROM completed and made available to the public. Lake Michigan and Lake Erie bathymetry products were completed and released in 1996 and 1998, respectively.

The new 36" x 50" poster portrays bathymetry at a contour interval of 2 meters using Transverse Mercator projection and a scale of 1:275,000. In addition to the main map, insets are included showing details of bottom relief in part of the Rochester Basin, and in the vicinity of Charity Shoal. Also included are text explaining the geology and geomorphology of the main lakefloor features, and a list of references for further reading.

Source data for the new Lake Ontario bathymetry includes the entire historic hydrographic sounding data base from the U.S. and Canada. These highly accurate hydrographic sounding data were collected over a 100-plus year period for nautical charting purposes by the U. S. Coast Survey, the U. S. Army Corps of Engineers, and the Canadian Hydrographic Service. Also used were multibeam bathymetric data collected by the University of New Brunswick's Ocean Mapping Group (UNB-OMG), with support of the Geological Survey of Canada (GSC), and CHS.

Many earlier interpretations of Lake Ontario geomorphology are confirmed by the new bathymetry; and new ideas have emerged which have significant implications for a number of environmental concerns:

  1. Linear and parallel ridges (3D view and flat 3D view) (1-2 km spacing, 15-30m relief), which trace a NE-SW arc on the floor of the Rochester Basin, resemble grooved topography in onshore drumlin fields north of the lake, and therefore may record flow direction of advancing ice and/ or subglacial meltwater.

  2. The Duck-Galloo Ridge is comprised of north-facing cuestas (20-30m relief) formed on resistant Ordovician limestones. Channels incising the Ridge terminate at its southern margin, which probably coincides with location of the Lake Ontario shoreline in early postglacial time.

  3. A small circular depression (3D view and flat 3D view) (1000m in diameter, 10-15m relief) with a continuous encircling rim coincides with the feature referred to as Charity Shoal. Origin of the feature remains unknown, although it resembles a simple impact crater.

  4. Strongly linear bathymetric features displaying the imprint of glaciation, or of exhumation of bedrock topography and structure, occur at intervals along almost all of the near-shore, where strong wave action and currents have evidently prevented deposition of postglacial muds, except in sheltered areas.

Since Lake Ontario lakefloor features are better described (or revealed for the first time) by the new bathymetry, new geographic names for these features have been proposed to the U. S. Board on Geographic Names (BGN), and these names have been adopted by BGN. The new names, shown on the new Lake Ontario poster, incorporate previously used names (names of precedence) where such names exist.

Completion of new and highly detailed bathymetry of the Great Lakes has been the objective of a long-term cooperative effort among scientists at NOAA/NESDIS's National Geophysical Data Center (NGDC) (now the National Centers for Environmental Information (NCEI)), NOAA/OAR's Great Lakes Environmental Research Laboratory (GLERL), and the Canadian Hydrographic Service (CHS). Financial support for this work to date has come from NOAA's ESDIM (Environmental Services Data and Information Management) Office, and from the aforementioned cooperating agencies.

Leaders of the effort are Troy L. Holcombe, Ph.D., research scientist at the NOAA/ University of Colorado Cooperative Institute for Research in Environmental Sciences (CIRES), David L. Divins, Ph.D., of NGDC, and David F. Reid, Ph.D., research scientist at GLERL. Principal compilers of the Lake Ontario bathymetry were William T. Virden of NGDC (now NCEI) and CIRES; and John S. Warren of CHS.

Data and imagery from Lake Ontario bathymetry is ready for incorporation into geographic information systems as base layers for various applications. Physical oceanographers and limnologists will be installing the bathymetry into their water circulation models.

High-resolution digital bathymetry makes possible meaningful quantitative estimates of available habitats for fish and other living organisms. In other lakes these estimates have been used to formulate regulations intended to prevent overfishing. Conversely, Great Lakes bathymetry is much in demand by anglers as an aid in locating the most promising areas for fishing.

This project is making Great Lakes bathymetry and various physical, chemical, and geological data readily available via posters, the internet, and CD-ROM. Ready availability has greatly increased the number and kind of uses for Great Lakes bathymetry, to the extent that more than ever before, this bathymetry is becoming a recognized national asset of the U. S. and Canada. Bathymetry posters and CD-ROMs are among NGDC's (now NCEI) demand products, and the bathymetry web pages are currently receiving "hits" at the rate of 55,000 per year.

Lake Ontario page, preview poster |

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