. Coast watch. Marine resources; Oceanography; Coastal zone management; Coastal ecology. sion, they say, are simply greater than our means for understanding them. Last fall the U. S. Environmental Protection Agency released the results of a study concerning the so-called greenhouse effect, created by the buildup of carbon dioxide in the upper atmosphere, and its presumed in- fluence on sea levels. The most publicized portions of the agency's report were the worst case projections, one of which suggested that sea level could rise off the Carolinas as much as two feet by the year 2040. Such a ra
. Coast watch. Marine resources; Oceanography; Coastal zone management; Coastal ecology. sion, they say, are simply greater than our means for understanding them. Last fall the U. S. Environmental Protection Agency released the results of a study concerning the so-called greenhouse effect, created by the buildup of carbon dioxide in the upper atmosphere, and its presumed in- fluence on sea levels. The most publicized portions of the agency's report were the worst case projections, one of which suggested that sea level could rise off the Carolinas as much as two feet by the year 2040. Such a rate would be four times or more the pre- sent rise, which has been estimated at one-third foot to one foot per century. While such a drastic sea level rise might indeed doom the barrier islands of North Carolina, Riggs says the pro- jections are too "iffy" to be useful now. Sea levels rise because of melting ice caps and glaciers, but also, some scientists believe, because of compac- tion in undersea sediments or a gradual sinking of the continental land masses. And, while the world's ice has been melting for thousands of years, it seems to have been melting less rapidly recently. Riggs says it is possible that the world is about to experience a shift toward more glaciation and slowly lowering seas. "The last four or five times that sea level changed, it changed about now in the cycle, toward more glaciation," Riggs says. But "about now" in the context of world geology could mean hundreds or thousands of years. And Riggs says he makes the point not to raise any hope that the sea may stop attacking and retreat soon, but only to illustrate that the greenhouse effect is only one of a number of forces shaping the seas and coasts. Another obstacle to understanding beach erosion is that the part of the beach we see is actually only a fraction of what is eroding. And what happens unseen under the wave may have more impact on the beaches than we have though
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