BOOK REVIEWS
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C. Douglas, S. Kearney, and
S.P. Leatherman, This is a timely volume,
marking the new millennium, by a team originally at the Department of Geography
in the University of Maryland (College Park, MD), though two have since
migrated to the International Hurricane Center (F.I.U.) In Miami (C.C.D. and
S.P.L.). Thanks to their courtesy I
have been provided with an advance copy. Their prevailing theme is that
even with a minimal mean rise of sea level during the 21st century,
if maintained, a catastrophic situation would arise. This is the result of a “collision course” between opposing
trends: the social migrations towards settlement in the coastal zone and the
rise of mean sea level anticipated in global warming scenarios. The first problem, the
coastward migration of populations, is recognized from the start as a sort-of
self-evident axiom. Why this lemming-like rush to the coast? No doubt it would
fill another volume, so for the moment we must accept as a “given” that a
mysterious centrifugal social force is driving human populations towards the
sea, not only in the United States, but almost worldwide. Most of the book is devoted
to the second problem, the observed rise of sea level during much of the 20th
century. After an introduction (by Douglas), there is an historical review of
the late Holocene by Kearney. This is particularly important because it
illustrates the fluctuating nature of NORMAL sea level, that is to say, prior
to the atmospheric pollution of the last century. A residual question is
always: how much of the 20th century change is natural, how much is
anthropogenic? Chapter 3 (by Douglas) considers the tide gauge results and what
they mean. The long-term records, in excess of 200 years, are unfortunately
very few in number, and the global departures (both positive and negative)
clearly support the “neotectonic” argument, i.e. the influence of local crustal
movements. W.R. Peltier compares the
global isotatic model with modern tide gauge data. The argument calls for the
progressive adjustment of the Earth’s crust, in a vertical sense, to the
retreat and final melting of the last glacial stage ice sheets. Those of the North Hemisphere greatly
exceeded all the rest, so that the isostatic adjustments are highly
skewed. Inasmuch as the last vestiges
of non-polar continental ice had melted by 6000 years ago, the slow isotatic
adjustment of both the Earth’s curst and the ocean surface (geiod) involve
complex calculations that need to be taken into regional evaluations. Some of those regional and
local matters are examined by Vivien Gornitz, especially those concerning
impoundment, groundwater “mining” and other hydrologic matters. The writer ( R.W.F.)
Organized a NATO Advanced Study of the subject (ed. By Paepe et al., 1990) on
Fuerteventura in the Canary Is. Since then there has bee much progress. Utilizing modern satellite
observations for monitoring purposes is only just now becoming feasible, as
discussed by R.S. Nerem and G.T. Mitchum. Some patterns of regional and global
change are beginning to show up. The statistics of tidegauge measurements on a
decadal level are examined by W. Sturges and B.G. Hong. Finally, in chapter 8, the
social and economic costs of the anticipated sea-level rise are appraised by
Stephen Leatherman, the lead inspiration. All-in-all, the volume shows the
benefits of careful planning and coordination. In contrast to the poor (or
non-existent) editing of many conference volumes, this approach provides a
highly readable study of the subject, which is likely to be quoted and referred
to for quite some years. There is
enough background information to provide working material for serious
researchers and policy makers. Much use has been made of graphical material, to
quote the author’s own words, “believing that graphics and data are the best
teachers”. As the authors clearly
recognize, there is far more to sea level change than simply beach erosion. To
begin with, there are extensive coastal belts in the high latitudes that are
still isostatically rising, some at rates in excess of the world average
sea-level rise. Tectonic and volcanic regions are crustally active, and their
dynamics also eclipse world sea-level patterns. Rightly, the authors comment
that the subject is complicated. The local dynamics always need to be sifted
out from the historical patterns that appear to be largely dictated by climatic
fluctuation. Evidence for the latter is derived from independent sources:
evidence such as glacier advances and retreats, tree-ring variations, lake
levels, and other long-term time series. During the next century we are talking
of sea-level changes in terms of mm/yr or cm/yr, but during the Holocene
natural fluctuations of sea level have sometimes exceeded several meters in a
century, which calls for remarkably sustained rates of change. This prompts the
reviewer to push his own interpretation of the major (I.E. sustained) sea-level
fluctuations over the last eight millennia, viz, their prime dependency of
long-term atmospheric pressure systems that may results in major shifts or even
complete reversals of wind systems and intensities (as suggested in a recent
Stockholm University thesis “Wind Controlled Climate” by Hans Jelbring, 1998). A simple relationship
between sea-level rise on the east coast of North America and net beach erosion
is often masked by coastal engineering projects and inlet dynamics, as pointed
out in a recent review by Leatherman, Zhang and Douglas (EOS, v 81(6), 55-56;
Feb. 8, 2000). That relationship is dictated on theoretical grounds by the
“Bruun Rule”, because nearshore water depth is increased, bringing more wave
energy to the beach face. However, the Bruun Rule is two-dimensional and has
been controversial because of longhsore dynamics. Several observers believe that angle of incidence of principal
wave action is the key. But, of course, much more research is needed. The
Douglas-Kearney-Leatherman volume is enormously enriched by the addition of a
CD-ROM on tide-gauge data with glacial isostatic adjustments suggested by
Peltier, together with an El Nino treatment (also assessable on the Web). Rhodes W. Fairbridge Columbia University % NASA-GISS, 2880 Broadway New York 10025
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