February 28, 2007
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FROM VOLUME 6, NUMBER 3, MARCH 1993
"Active Volcanism beneath the West Antarctic Ice Sheet and
Implications for Ice-Sheet Stability," D.D. Blankenship
(Inst. Geophys., Univ. Texas, Austin TX 78759), R.E. Bell et al., Nature, 361(6412),
526-529, Feb. 11, 1993.
The response of the West Antarctic ice sheet to climatic
change is a concern because its collapse would cause a global sea
level rise of 6 meters. This paper presents evidence for active
volcanism and associated heat flow beneath the sheet where ice
streaming begins, raising the possibility that the stability of
the sheet is controlled by geological conditions independent of
climate, and that penetration of ocean water sufficiently inland
could trigger collapse. (See Res. News.)
related items from Nature, 361(6412), Feb. 11,
"Carbon Reserves Released?" R.S. Webb (Nat. Geophys.
Data Ctr., 325 Broadway, Boulder CO 80303), J.T. Overpeck,
497-498. Although in the long term it seems that increased
atmospheric CO2 will lead to increased terrestrial
carbon storage, the following two studies show that global
warming could add to the CO2 burden over short
durations (50-100 years).
"Recent Change of Arctic Tundra Ecosystems from a Net
Carbon Dioxide Sink to a Source," W.C. Oechel (Dept. Biol.,
San Diego State Univ., San Diego CA 92182), S.J. Hastings et al.,
520-523. Presents data indicating that the tundra on the North
Slope of Alaska, a net carbon sink during historic and recent
geologic times, has recently become a source of CO2,
coincident with recent warming in the Arctic. Regardless of the
cause of the recent warming, results suggest that tundra
ecosystems may exert a positive feedback on atmospheric CO2
and any greenhouse warming.
"The Transient Response of Terrestrial Carbon Storage to
a Perturbed Climate," T.M. Smith (Dept. Environ. Sci., Univ.
Virginia, Charlottesville VA 22903), H.H. Shugart, 523-526.
Results from two GCMs show that vegetation and soil changes could
be significant sources of CO2 following greenhouse
warming, increasing atmospheric concentrations by up to a third
of the present level.
related items from Nature, 361(6411), Feb. 4, 1993:
"Flickers within Cycles," S. Lehman (Woods Hole
Oceanog. Inst., Woods Hole MA 02543), 404-405. Results such as
those in the following entry pose climatologists and policy
makers with a dilemma: how long will we have to wait before we
are convinced that we are seeing or not seeing a greenhouse
"The `Flickering Switch' of Late Pleistocene Climate
Change," K.C. Taylor (Desert Res. Inst., Univ. Nevada, Reno
NV 89512), G.W. Lamorey et al., 432-436. Electrical conductivity
measurements from a Greenland ice core reveal a previously
unrecognized mode of rapid climate variation--fluctuations of the
scales of <5-20 years, reflecting oscillations in the dust
content of the atmosphere. This `flickering' between two climatic
states would seem to require rapid reorganizations in atmospheric
related items from ibid.:
"Learning from the Past," V. Baker (Dept. Geosci.,
Univ. Arizona, Tucson AZ 85721), 402-403. Comments on the science
and policy implications of the following entry.
"Large Increases in Flood Magnitude in Response to Modest
Changes in Climate," J.C. Knox (Dept. Geog., Univ.
Wisconsin, Madison WI 53706), 430-432. A 7,000-year geological
record of overbank floods for upper Mississippi river tributaries
provides concrete evidence for a high sensitivity of flood
occurrence to changing climate. Greatly differing flood
magnitudes were associated with mean annual temperature changes
of only 1·-2·C.
related items from Nature, 361(6410), Jan. 28,
"The Elusive Arctic Warming," J.E. Walsh (Dept.
Atmos. Sci., Univ. Illinois, Urbana IL 61801), 300-301. Although
the findings of the following entry apparently run counter to
model predictions of greenhouse warming, they are not necessarily
at odds when viewed in a broader context.
"Absence of Evidence for Greenhouse Warming over the
Arctic Ocean in the Past 40 Years," J.D. Kahl (Dept.
Geosci., Univ. Wisconsin-Milwaukee, POB 413, Milwaukee WI 53201),
D.J. Charlevoix et al., 335-337. Analysis of over 27,000
temperature profiles for the period 1950-1990 shows no evidence
of the large surface warming trends predicted by models. The
discrepancy suggests that present climate models do not
adequately incorporate the physical processes important in the
related items from Nature, 361(6409), Jan. 21,
"Northward March of Spruce," J. Pastor (Natural
Resour. Res. Inst., Univ. Minnesota, Duluth MN 55811), 208-209.
Discusses the following entry, and some questions it raises.
"Rapid Response of Treeline Vegetation and Lakes to Past
Climate Warming," G.M. MacDonald (Dept. Geog., McMaster
Univ., Hamilton ON L8S 4K1, Can.), T.W.D. Edwards et al.,
243-246. Presents paleoecological evidence for changes in
terrestrial vegetation and lake characteristics during an episode
of climate warming 4,000-5,000 years ago in Canada. The initial
transformation--from tundra to forest-tundra--took only 150
years, roughly the time period used in modeling the response of
boreal forests to greenhouse warming.
"Long-Term Solar Brightness Changes Estimated from a Survey
of Sun-Like Stars," G.W. Lockwood (Lowell Observ., 1400 W.
Mars Hill Rd., Flagstaff AZ 86001), B.A. Skiff et al., Nature, 360(6405),
653-655, Dec. 17, 1992.
Presents a compilation of observations of 33 Sun-like stars,
which show year-to-year brightness changes that greatly exceed
analogous solar fluctuations. Results suggest that the Sun is in
an unusually steady phase compared to similar stars, and that
reconstructing the past historical brightness record from sunspot
records (to interpret temperature trends) may be more risky than
"Marine Sciences in the Coming Decades," C. Wunsch
(Dept. Earth Sci., Mass. Inst. Technol., Cambridge MA 02139), Science, 259(5093),
296-297, Jan. 15, 1993.
Discusses a trend toward steady or declining support for
marine sciences and possible remedies, the subject of the recent
National Academy of Sciences report Oceanography in the Next
"Remote Sensing of Oceanic Biology in Relation to Global
Climate Change," J. Aiken (NERC Plymouth Marine Lab.,
Prospect Pl. W. Hoe, Plymouth PL1 3DH, UK), G.F. Moore, P.M.
Holligan, J. Phycol., 28(5), 579-590, Oct. 1992.
A review of the wealth of information that has been obtained
from the Coastal Zone Color Scanner (CZCS) and from newer sensors
such as SeaWiFS. Discusses information still needed for climate
change research, such as fluxes of DMS relevant to cloud-climate
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