The
Gulf Stream is a warm ocean current in the North Atlantic Ocean,
flowing from the Gulf of Mexico, northeast along the US coast
to Nantucket Island, and from there to the British Isles and the
Norwegian Seas.
First
described by the Spanish navigator and explorer Juan Ponce de
León early in the 16th century, the Gulf Stream's course
was originally charted in 1770, a collaboration of Benjamin Franklin
and Timothy Folger. In 1844, systematic surveying of the stream
was undertaken by the United States Coast and Geodetic Survey.
More recent efforts occurred in the early 1930's, by the ketch
Atlantis of the Woods Hole Oceanographic Institution.
The
Gulf of Mexico, once thought to be the source of the Stream, actually
contributes very little to its flow. The Gulf Stream results when
two strong currents, the North and South Equatorial Currents,
mingle in the passage between the Windward Islands and the Caribbean
Sea. Off the southern coast of Florida, it is strengthened by
other currents from the northern coast of Puerto Rico and from
the Bahamas to the east.
The
true Gulf Stream flows between the Straits of Florida, and the
Grand Banks. However, it is part of a much larger Gulf Stream
System, that covers the entire northward and eastward flow from
the Straits of Florida, including the branches crossing the North
Atlantic from the region south of the Newfoundland Banks.
About
1,500 miles (2,414 km) northeast of Cape Hatteras, in the area
of the Grand Banks, the warm Gulf Stream waters come close to
the cold, southward-flowing Labrador Current. The contact of cold,
humid air moving over the Labrador Current with the warm surface
waters of the Gulf Stream causes widespread condensation. This
climatic condition causes the region to have one of the highest
incidences of fog in the world.
In
the western Atlantic, the current's deep-blue water, with its
higher temperature and salinity, is readily distinguishable from
surrounding waters, particularly along its well-defined western
margin.
A
major contribution of the Gulf Stream System is its warming effect
upon the climates of adjacent land areas. In winter, the air over
the ocean west of Norway is more than 40° F (22° C)
warmer than the average for that latitude, one of the greatest
temperature anomalies in the world. The prevailing westerly winds
carry the warmth and moisture of the ocean to northwestern Europe,
giving Bergen, Norway, at 60 degrees north latitude, an average
high temperature for its coldest month of 34° F (1°
C), while Reykjavík, Iceland, 4 degrees of latitude farther
north, has a 31° F (-0.6° C) average for its coldest
month.
Interestingly,
along the western North Atlantic, where the winds are predominantly
from the shore, the Gulf Stream has little effect. Halifax, Nova
Scotia, nearly 1,000 miles (1,609 km) south of Bergen, averages
only 23° F (-5° C) during its coldest month.
In
southwestern England, the climatic modification produced by the
current is reflected in the extraordinary mildness of the winters
at this northern latitude. Here, winter vegetables and flowers
are grown, and lemon trees are seen in southern Devonshire.
And,
let's not forget the palm trees in Scotland!!
Logan
Botanic Garden is in the parish of Kirkmaiden, in the Rhinns
of Galloway, a narrow peninsula that juts out into the Irish Sea,
at the extreme south-west of Scotland.
Our
friend, the Gulf Stream, gives these gardens a virtual sub- tropical
climate. Thus, the Logan features plants usually identified with
warmer areas of the world, including palm trees.
What
a different world this would have been, absent the Gulf Stream,
with the British Isles and Norway occupying a frozen tundra!