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Table 4. Beaufort Wind Scale Related to Sea States
Bea ufort Win d Win d Sea Wave Sea
Number Type Speed Surface Hei~?ht State
(kno~s) (feet)
0 Calm 50 8
Greenland's gigantic ice cap are the source of most icebergs in the North Atlantic. Huge
blocks with sharp peaks and jagged bellies break off in springtime, a process called "calving,"
then drift southward with ocean currents. Icebergs float, because ice is less dense than sea
water, but about nine-tenths of their mass are concealed. Many tower 250 feet (76 mei.ers)
or more above the surface and spread a quarter of a mile (400 meters) or so below. Titanic's
catastrophe occurred at 41" 46' North Latitude, on a line with Madrid, Spain, although most
icebergs in the Atlantic melt before they float that far south. Fewer bergs appear in the North
Pacific, because "breeding" grounds are restricted, but those that break off the Antarctic ice
shelf are immense, numerous, and drift farther toward the Equator than those from
Greenland. Associated hazards, however, are less owing to lighter seagoing traffic.
Pack ice, which perennially covers most of the Arctic Ocean, produces flat-topped, steep-
sided, tabular floes of which all proceed independently before dominant winds with narrow
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.~4 PART ONE: PHYSICAL GEOGRAPHY