FIGURE 13

(a) Annual runoff from the North American continent into the Arctic Basin, 1930-67, with mean (solid line) and ± 1 standard deviation (dashed line) indicated; (b) lagged cross-correlation between runoff (above) and Koch Index of ice severity (below) at the Icelandic coast, 1915-75; (c) the Koch sea-ice severity index for Iceland. (All from Mysak and Power, 1991; reprinted with permission of the Canadian Meteorological and Oceanographic Society.)

that is inherent in such processes. The approximately 14-year circulation period of the subpolar gyre is plainly one such control, but the decadal regimes in southeastern U.S. air temperature shown in Figure 11, the 6.7-year spectral maximum in the North Atlantic oscillation index (Rogers,

FIGURE 14

Anomalies of (a) temperature and (b) salinity in June at 25 m depth in a study area between Iceland and Jan Mayen (67- 69°N, 11-15°W). The long-term means, 1950-58, are also shown. (From Malmberg, 1973; reprinted with permission.)

FIGURE 15

Schematic diagram illustrating the suppression of convection north of Iceland as upper-ocean salinities decrease below 34.7. (From Dickson et al., 1988; reprinted with permission of Pergamon Press.)

1984), the multi-year advective time lag of ice drift from the Beaufort Sea to Greenland and Labrador (Mysak and Power, 1991; Mysak and Manak, 1989) plainly have the potential to lend a degree of periodicity to the process. Conceptual models for these periodic anomalies—some of great complexity (see Figure 3 of Mysak and Power, 1991)—have been proposed (see also Darby and Mysak, 1993; Ikeda, 1990). Under this rationale the Great Salinity Anomaly was merely a more obvious, high-amplitude iteration of a regular event.

To demonstrate a global role for Denmark Strait exchanges, there can be few more eloquent illustrations than Figure 16 (from Charles and Fairbanks, 1992), in which the d¹³C history in benthic forams from the sea-floor sedi-