Geoscience Reference
In-Depth Information
cape, in the Mid-Atlantic region, where the glacier never reached, a low-lying, mostly linear coastal plain pre-
vails, consisting of sediments eroded from the Appalachian Mountains then molded by the ocean's tides, cur-
rents, and storms into sandy beaches, barrier islands, and coastal lagoons.
Far from shore, at the Tail of Newfoundland's Grand Banks, the cold, iceberg-studded Labrador Current,
swinging down from the Canadian Arctic and Greenland, and the warm Gulf Stream, curving up from the trop-
ics, vie for supremacy. The first chronicler of New France, Marc Lescarbot, observed this strange conjunction
on his first voyage to the New World, in 1606:
I discovered something remarkable that a philosopher of nature should wonder about. On 18 June 1606 at
45 degrees latitude and at a distance of one hundred and twenty leagues to the east of the banks of New-
foundland, we found ourselves surrounded by very warm water, although the air was cold. Yet on 21 June
we were suddenly caught in such a fog that one would have thought oneself to be in January, and the sea
was extremely cold.
Lescarbot was witness to the clash of the titans, whereby both of these powerful currents are deflected: the
Gulf Stream to the northeast, where it warms northern Europe as the North Atlantic Current; the Labrador Cur-
rent to the southwest, where it cools the North American coast. While robbing the Northwest Atlantic of a
more equable climate, the Labrador Current has bestowed benefits to both wildlife and society. These cold,
plankton-rich waters are the foundation of the legendary productivity of Newfoundland's Grand Bank and its
more southerly counterpart, Georges Bank, in the Gulf of Maine—two of the richest fishing regions in the
world.
Diverse Waters
The Northwest Atlantic—the subject of this topic—is not a homogenous body of water, which is hardly sur-
prising given its size and reach. As we have already seen, the warm Gulf Stream exerts a moderating influence
in the southernmost region, whereas in the north the cold Labrador Current is dominant. Moving from north to
south, we encounter water masses that are dramatically different, from very cold, subarctic waters along the
Labrador coast to the Strait of Belle Isle, to the cold-temperate waters of the Canadian Maritime Provinces and
northern New England, and, finally, to the warmer, temperate waters of the Mid-Atlantic region, between Cape
Cod and Cape Hatteras. As a whole, the Northwest Atlantic comprises an ecozone, which is the largest biogeo-
graphic unit. South of Cape Hatteras, we enter the Wider Caribbean ecozone—an ocean of warm waters and
warm-water species in sharp contrast to the cool waters and cold-water species of the Northwest Atlantic eco-
zone.
The diverse marine and terrestrial environments within the Northwest Atlantic can best be understood by
adopting an ecoregional approach. A useful, if sometimes flexible, concept, an ecoregion is a large, geograph-
ically distinct area of land or water sharing a large majority of species and environmental conditions that inter-
act in ways leading to its persistence over long periods of time. It is smaller than an ecozone and larger than an
ecosystem. The ecosystem is the basic unit of nature and itself varies in scale. A lake, a forest, and a bog are
examples of ecosystems, though a larger geographic unit encompassing all of them might also be considered
an ecosystem. Within an ecosystem, living organisms and their environment are inseparable, with a constant
exchange of energy and matter, in the form of food, nutrients, water, and waste, occurring between its living
and nonliving parts.
Differences in marine environments are more difficult to determine than differences in terrestrial environ-
ments. Oceanographic factors, such as currents, tides, water temperature, and salinity, set them apart. Due to
the far-reaching, ever-present influence of the ocean, these define the nature not only of the marine life found
there but of life along the coast and on land. The types and numbers of organisms are also useful criteria in
drawing boundaries.
