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Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999

FROM VOLUME 4, NUMBER 3, MARCH 1991

PROFESSIONAL PUBLICATIONS...
GLOBAL CARBON CYCLE

Item #d91mar34

"Isotopic Composition of Atmospheric CO₂ Inferred from Carbon in C4 Plant Cellulose," B.D. Marino (Dept. Earth Sci., Harvard Univ., Cambridge MA 02138), M.B. McElroy, Nature, 349(6305), 127-131, Jan. 10, 1991.

Shows that carbon in C4 plants preserves an isotopic record of the CO₂ used in photosynthesis, and that data for the maize plant yield results for the isotopic composition of atmospheric CO₂ that are consistent with measurements of modern air trapped in polar ice. Studies of intact and fossil (dating to 1500 A.D.) C4 material provide a way to extend the isotopic record of atmospheric CO₂ into the past, complementing data from other sources.

Item #d91mar35

"Air-Sea Gas Exchange in Rough and Stormy Seas Measured by a Dual-Tracer Technique," A.J. Watson (Plymouth Marine Lab., Prospect Pl., West Hoe, Plymouth PL1 3DH, UK), R.C. Upstill-Goddard, P.S. Liss, ibid., 145-147.

Reports first results from the application of a tracer technique which enables accurate measurements to be made over periods of 24-72 hours, including the first determination of gas exchange in stormy conditions. Results suggest lower CO₂ exchange rates than those obtained by 14C budgeting, and favor recent lower estimates of the global oceanic sink for anthropogenic CO₂.

Item #d91mar36

"Arctic Lakes and Streams as Gas Conduits to the Atmosphere: Implications for Tundra Carbon Budgets," G.W. Kling (Ecosyst. Ctr., Marine Biol. Lab., Woods Hole MA 02543), G.W. Kipphut, M.C. Miller, Science, 251(4991), 298-301, Jan. 18, 1991.

Measurements of the partial pressure of CO₂ in 29 aquatic ecosystems across arctic Alaska showed that in most cases CO₂ was released to the atmosphere. This CO₂ probably originates in terrestrial environments, by erosion of particulate carbon plus groundwater transport of dissolved carbon. If this mechanism is typical of that of other tundra areas, then current estimates of the arctic terrestrial sink for atmospheric CO₂ may be 20% too high.

Item #d91mar37

"Long-Term Changes in Amplitudes of Atmospheric CO₂ Concentrations at Ocean Station P and Alert, Canada," Y.-H. Chan, C.S. Wong, Tellus, 42B(4), 330-341, 1990. (See Prof. Pubs./Trend Analysis, this Global Climate Change Digest issue--Mar. 1991.)

Item #d91mar38

"Vegetation an Unlikely Answer," W.H. Schlesinger (Dept. Bot., Duke Univ., Durham NC 27706), Nature, 348(6303), 679, Dec. 20-27, 1990.

Discusses recent work on the role of land, plants and soils in the uptake of enhanced CO₂, such as that by Adams (next entry). Because of future human activity, the terrestrial biosphere is unlikely to act as a significant future carbon sink.

Item #d91mar39

"Increases in Terrestrial Carbon Storage from the Last Glacial Maximum to the Present," J.M. Adams (Dept. Bot., Univ. Cambridge, Downing St., Cambridge CB3 2EA, UK), H. Faure et al., ibid., 711-714.

Presents palynological, pedological and sedimentological evidence indicating that the amount of carbon in vegetation, soils and peatlands may have been smaller during the Last Glacial Maximum (LGM) by about 1.3x1012 tons, and may have more than doubled since then. Oceanic CO₂ reservoirs seem to be the only possible source of present levels of this large quantity of carbon. The terrestrial vegetation and soil carbon reservoirs should be seen as a factor tending to damp the oceanically driven glacial-interglacial CO₂ fluctuations during the LGM.

Item #d91mar40

"Evidence from Chronosequence Studies for a Low Carbon-Storage Potential of Soils," W.H. Schlesinger (Dept. Bot., Duke Univ., Durham NC 27706), Nature, 348(6298), 232-234, Nov. 15, 1990.

Although Pentice and Fung have suggested that terrestrial vegetation and soils would act as a large sink for atmospheric CO₂ if its concentration were twice the present level, found that production of refractory humic soil substances sequesters only about 0.4x1015 g C yr-1 from the atmosphere, or just 0.7% of terrestrial net primary production. Moreover, the loss of humic materials from cultivated lands is greatly in excess of the rate of formation of humus in undisturbed lands, transforming the soil pool from a small sink to a large source of atmospheric CO₂.

Item #d91mar41

"Hydroxyl Radical Photoproduction in the Sea and Its Potential Impact on Marine Processes," K. Mopper (Chem. Dept., Washington State Univ., Pullman WA 99164), X. Zhou, Science, 250(4981), 661-664, Nov. 2, 1990.

Photochemical production rates and steady-state concentrations of OH radicals were measured in sunlight-irradiated seawater. Found that dissolved organic matter is degraded more readily by OH and its daughter radicals in the deep sea than in open-ocean surface water. This result may bear in part on major discrepancies among current methods for measuring dissolved organic carbon in seawater.

Item #d91mar42

"Intensification of Recycling of Organic Matter at the Sea Floor near Ocean Margins," R.A. Jahnke (Skidway Inst. Oceanog., POB 13687, Savannah GA 31416), C.E. Reimers, D.B. Craven, Nature, 348(6296), 50-54, Nov. 1, 1990.

A study of benthic exchange and metabolism performed off the California continental shelf indicates that across the northeast Pacific, half the input of organic carbon to the sea floor occurs within 500 km of the continental shelf. Measured rates of benthic carbon oxidation exceed the fluxes of organic carbon determined from previous sediment-trap studies by a factor of three.

Item #d91mar43

"Estimating Atmospheric CO₂," N.J. Shackleton (Godwin Lab. Quat. Res., New Museums Site, Free School Ln., Cambridge CB2 3RS, UK), ibid., 347(6292), 427-428, Oct. 4, 1990. Discusses a new approach to estimating the history of CO₂ partial pressure in the ocean surface waters, proposed by Jasper and Hayes (next entry). It should extend the CO₂ record well beyond the start of the ice-core record, and elucidate changes in the dynamic equilibrium of CO₂ between the atmosphere and the sea surface.

Item #d91mar44

"A Carbon Isotope Record of CO₂ Levels during the Late Quaternary," J.P. Jasper (Biogeochem. Labs., Indiana Univ., Bloomington IN 47405), J.M. Hayes, ibid., 462-464.

A signal related to atmospheric CO₂ levels, seen in the isotope record of a hemipelagic sediment core, can be correlated with that of the Vostok ice core. This should permit extrapolation of CO₂ records to times earlier than those for which ice-core records are available.

Item #d91mar45

"Dynamics of Dissolved Organic Carbon in the Northwestern Indian Ocean," M.D. Kumar (Nat. Inst. Oceanog., Dona Paula, Goa 403 004, India), A. Rajendran et al., Marine Chem., 31, 299-316, 1990. Reports non-conservative behavior of DOC in the northwestern Indian Ocean, which contrasts with earlier reports of conservative behavior, by studying this parameter together with other carbon and nitrogen components.

Item #d91mar46

"Bombs and Ocean Carbon Cycles," J.R. Toggweiler (Geophys. Fluid Dyn. Lab., Princeton Univ., POB 308, Princeton NJ 08542), Nature, 347(6289), 122-123, Sep. 13, 1990. Discusses work by Druffel and Williams that supports the dissolved organic pathway of carbon transport to the deep ocean. (See next entry.)

Item #d91mar47

"Identification of a Deep Marine Source of Particulate Organic Carbon Using Bomb 14C," E.R.M. Druffel (Woods Hole Oceanog. Inst., Woods Hole MA 02543), P.M. Williams, ibid., 172-174.

The influx of radiocarbon 14C from earlier nuclear bomb tests was evaluated by radiocarbon dating of pelagic organisms in the North Pacific. The per mil deviation from the `standard' activity of nineteenth century wood (delta 14C) was found to have a significant gradient with depth, an observation that would not be expected according to long-standing assumptions about carbon cycling in the water column. Discusses the roles of dissolved organic carbon and sinking particulate organic carbon.

Item #d91mar48

"Dissolved Organic Carbon in the Ocean," E.A. Romankevich (Shirshov Inst. Oceanol., USSR Acad. Sci., 23 Krasikova, SU-117218, Moscow, USSR), S.V. Ljutsarev, Marine Chem., 30(1-3), 161-178, Aug. 1990. Soviet investigations of DOC in the Peruvian upwelling area, the Bay of Bengal, the Philippine Sea and the Antarctic area are summarized, discussed and compared to results of Sugimura and Suzuki for the Philippine Sea.

Item #d91mar49

"Carbon Balance in Tussock Tundra under Ambient and Elevated Atmospheric CO₂," N.E. Grulke,...W.C. Oechel (Biol. Dept., San Diego State Univ., San Diego CA 92182) et al., Oecologia, 83(4), 485-494, July 1990.

Whole ecosystem CO₂ flux was measured in situ on the North Slope of Alaska. Elevated CO₂ caused greater carbon acquisition and there was a net loss of CO₂ under ambient conditions at this upland site. The measurements indicate a current loss of carbon, possibly the result of recent climatic changes, and suggest little if any long-term stimulation of ecosystem carbon acquisition by increases in atmospheric CO₂.

Item #d91mar50

"Biological Production off Southern California Is Linked to Climatic Change," C.B. Lange (Scripps Inst. Oceanog., Univ. Calif. Geol. Res. Div., La Jolla CA 92093), S.K. Burke, W.H. Berger, Clim. Change, 16(3), 319-329, June 1990.

Decreases in the flux of diatoms in the last few decades, indicated by marine laminated sediments, are interpreted in terms of mean temperatures and the strength of the Aleutian Low and associated oceanic mixing and upwelling. The possibility that low coastal production could provide positive feedback to global warming through reduced CO₂ uptake is considered.