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1.
Shallow, seaward portions of modern coral reefs produce about 4 kilograms of calcium carbonate per square meter per year, and protected areas produce about 0.8 kilogram per square meter per year. The difference is probably largely a function of water motion. The more rapid rate, equivalent to a maximum vertical accretion of 3 to 5 millimeters per year, places an upper limit on the potential of modern coral reef communities to create a significant vertical structure on a rising sea. 相似文献
2.
Limestone-bearing gravel, the newly named Hulopoe Gravel, blankets the coastal slopes on Lanai. The deposit, which reaches a maximum altitude of 326 meters, formerly was believed to have been deposited along several different ancient marine strandlines, but dated submerged coral reefs and tide-gauge measurements indicate that the southeastern Hawaiian Islands sink so fast that former worldwide high stands of the sea now lie beneath local sea level. Evidence indicates that the Hulopoe Gravel and similar deposits on nearby islands were deposited during the Pleistocene by a giant wave generated by a submarine landslide on a sea scarp south of Lanai. 相似文献
3.
Menard HW 《Science (New York, N.Y.)》1983,220(4600):913-918
Organic reefs and shore erosion record the intersection of sea level with islands. From this record it is possible to reconstruct the history of vertical movement of the islands and the adjacent deep sea floor, including midplate swells. As judged by coral thickness, islands with barrier reefs sink as though they were on thermally youthful crust regardless of the actual age. Reefless islands do not sink until truncated by erosion. Apparently, thermal subsidence is balanced by isostatic uplift in response to erosion. Barrier reefs prevent wave erosion of encircled volcanoes and capture products of stream erosion so that isostatic uplift is eliminated. Insular shelves widen initially at rates of 0.6 to 1.7 kilometers per million years; the rates decrease with time. Thus the subsidence of islands depends on the size of the is land and the presence of reefs, and it may not always be the same as that of the surrounding oceanic crust. 相似文献
4.
Samples of Holocene fossil coral from uplifted reefs of three tectonically distinct, yet geographically proximal regions of Taiwan have been dated by uranium-series and (14)C isotopes. Applying corrections for altitude change caused by sea level fluctuations enables evaluation of long-term average Holocene uplift rates for three areas across an active convergent margin: (i) the Hengchun Peninsula of the Eurasian tectonic plate; (ii) the Eastern Coastal Range of Taiwan, a plate boundary; and (iii) two offshore islands, Lanyu and Lutao, both situated on the leading edge of the adjoining Philippine Plate. The data indicate that while all three areas have experienced uplift through the Holocene, plate collision has caused significantly higher uplift rates in the region directly along the plate boundary. 相似文献
5.
Digital elevation models of the Northern and Southern Patagonia Icefields of South America generated from the 2000 Shuttle Radar Topography Mission were compared with earlier cartography to estimate the volume change of the largest 63 glaciers. During the period 1968/1975-2000, these glaciers lost ice at a rate equivalent to a sea level rise of 0.042 +/- 0.002 millimeters per year. In the more recent years 1995-2000, average ice thinning rates have more than doubled to an equivalent sea level rise of 0.105 +/- 0.011 millimeters per year. The glaciers are thinning more quickly than can be explained by warmer air temperatures and decreased precipitation, and their contribution to sea level per unit area is larger than that of Alaska glaciers. 相似文献
6.
Accelerated sea-level rise from West Antarctica 总被引：1，自引：0，他引：1
Thomas R Rignot E Casassa G Kanagaratnam P Acuña C Akins T Brecher H Frederick E Gogineni P Krabill W Manizade S Ramamoorthy H Rivera A Russell R Sonntag J Swift R Yungel J Zwally J 《Science (New York, N.Y.)》2004,306(5694):255-258
Recent aircraft and satellite laser altimeter surveys of the Amundsen Sea sector of West Antarctica show that local glaciers are discharging about 250 cubic kilometers of ice per year to the ocean, almost 60% more than is accumulated within their catchment basins. This discharge is sufficient to raise sea level by more than 0.2 millimeters per year. Glacier thinning rates near the coast during 2002-2003 are much larger than those observed during the 1990s. Most of these glaciers flow into floating ice shelves over bedrock up to hundreds of meters deeper than previous estimates, providing exit routes for ice from further inland if ice-sheet collapse is under way. 相似文献
7.
Coral reefs resemble islands of productive habitats where fishes aggregate, forage, and spawn. Although it has been suggested that some reef fishes use biogenic chemicals as aggregation cues, specific chemicals have not been identified. Dimethylsulfoniopropionate (DMSP), a secondary metabolite of many marine algal species, is released during foraging by higher-order consumers. DMSP has been studied intensively for its role in oceanic sulfur cycles and global climate regulation, but its ecological importance to marine fishes is unknown. We present evidence that planktivorous reef fishes will aggregate to experimental deployments of DMSP over coral reef habitats in the wild. 相似文献
8.
Shepard FP Curray JR Newman WA Bloom AL Newell ND Tracey JI Veeh HH 《Science (New York, N.Y.)》1967,157(3788):542-544
Investigation of 33 islands, scattered widely across the Caroline and Marshall Island groups in the Central Pacific revealed no emerged reefs in which corals had unquestionably formed in situ, or other direct evidence of postglacial high stands of sea level. Low unconsolidated rock terraces and ridges of reefflat islands, mostly lying between tide levels, were composed of rubble conglomerates; carbon-14 dating of 11 samples from the conglomerates so far may suggest a former slightly higher sea level (nine samples range between 1890 and 3450 and one approaches 4500 years ago). However, recent hurricanes have produced ridges of comparable height and material, and in the same areas relics from World War II have been found cemented in place. Thus these datings do not in themselves necessarily indicate formerly higher sea levels. Rubble tracts are produced by storms under present conditions without any change in datum, and there seems to be no compelling evidence that they were not so developed during various periods in the past. 相似文献
9.
Radiocarbon and thorium-230 dates of uplifted coral reef terraces on New Guinea appear to support theories of glaciation which utilize Milankovitch cycles as a controlling trigger mechanism. In addition to high sealevel stands recognized by other workers, the New Guinea data clearly indicate a marine transgression between 50,000 and 35,000 years before the present. A eustatic sea level curve reconstructed from field observations and radiometric dates shows a close correlation with temperature fluctuations in high latitudes as predicted by astronomical data. 相似文献
10.
Roemmich D 《Science (New York, N.Y.)》1992,257(5068):373-375
Hydrographic time-series data recorded during the past 42 years in the upper 500 meters off the coast of southern California indicate that temperatures have increased by 0.8 degrees C uniformly in the upper 100 meters and that temperatures have risen significantly to depths of about 300 meters. The effect of warming the surface layer of the ocean and there by expanding the water column has been to raise sea level by 0.9 +/- 0.2 millimeter per year. Tide gauge records along the coast are coherent with steric height and show upward trends in sea level that vary from about 1 to 3 millimeters per year. 相似文献
11.
The increase in sea level from the last glacial maximum has been derived from a siliciclastic system on the tectonically stable Sunda Shelf in Southeast Asia. The time from 21 to 14 thousand calendar years before the present has been poorly covered in other records. The record generally confirms sea-level reconstructions from coral reefs. The rise of sea level during meltwater pulse 1A was as much as 16 meters within 300 years (14.6 to 14.3 thousand years ago). 相似文献
12.
Kleypas JA Buddemeier RW Archer D Gattuso JP Langdon C Opdyke BN 《Science (New York, N.Y.)》1999,284(5411):118-120
A coral reef represents the net accumulation of calcium carbonate (CaCO3) produced by corals and other calcifying organisms. If calcification declines, then reef-building capacity also declines. Coral reef calcification depends on the saturation state of the carbonate mineral aragonite of surface waters. By the middle of the next century, an increased concentration of carbon dioxide will decrease the aragonite saturation state in the tropics by 30 percent and biogenic aragonite precipitation by 14 to 30 percent. Coral reefs are particularly threatened, because reef-building organisms secrete metastable forms of CaCO3, but the biogeochemical consequences on other calcifying marine ecosystems may be equally severe. 相似文献
13.
By reconstructing the history of water impoundment in the world's artificial reservoirs, we show that a total of approximately 10,800 cubic kilometers of water has been impounded on land to date, reducing the magnitude of global sea level (GSL) rise by -30.0 millimeters, at an average rate of -0.55 millimeters per year during the past half century. This demands a considerably larger contribution to GSL rise from other (natural and anthropogenic) causes than otherwise required. The reconstructed GSL history, accounting for the impact of reservoirs by adding back the impounded water volume, shows an essentially constant rate of rise at +2.46 millimeters per year over at least the past 80 years. This value is contrary to the conventional view of apparently variable GSL rise, which is based on face values of observation. 相似文献
14.
The elevations and ages of a sequence of three uplifted Pleistocene coral reefs on the Northwest Peninsula of Haiti have been determined. With the assignment of a sea level of +6 meters (relative to the present day) at 130,000 years before present and constant uplift of the reefs, the data indicate that sea level stood -10 and -13 meters at 108,000 and 81,000 years before present, respectively. These results are in substantial agreement with those reported for Barbados and New Guinea and support the hypothesis of constant uplift for each area. Sea level data from raised reefs indicate that the interglacial marine oxygen isotope oscillations during oxygen isotope stage 5 are a result of 30 percent ice volume effects and 70 percent temperature effects. 相似文献
15.
Carpenter KE Abrar M Aeby G Aronson RB Banks S Bruckner A Chiriboga A Cortés J Delbeek JC Devantier L Edgar GJ Edwards AJ Fenner D Guzmán HM Hoeksema BW Hodgson G Johan O Licuanan WY Livingstone SR Lovell ER Moore JA Obura DO Ochavillo D Polidoro BA Precht WF Quibilan MC Reboton C Richards ZT Rogers AD Sanciangco J Sheppard A Sheppard C Smith J Stuart S Turak E Veron JE Wallace C Weil E Wood E 《Science (New York, N.Y.)》2008,321(5888):560-563
The conservation status of 845 zooxanthellate reef-building coral species was assessed by using International Union for Conservation of Nature Red List Criteria. Of the 704 species that could be assigned conservation status, 32.8% are in categories with elevated risk of extinction. Declines in abundance are associated with bleaching and diseases driven by elevated sea surface temperatures, with extinction risk further exacerbated by local-scale anthropogenic disturbances. The proportion of corals threatened with extinction has increased dramatically in recent decades and exceeds that of most terrestrial groups. The Caribbean has the largest proportion of corals in high extinction risk categories, whereas the Coral Triangle (western Pacific) has the highest proportion of species in all categories of elevated extinction risk. Our results emphasize the widespread plight of coral reefs and the urgent need to enact conservation measures. 相似文献
16.
Adey WH 《Science (New York, N.Y.)》1978,202(4370):831-837
Windward reef morphogenesis is a dynamic process directly controlled by the growth potential of dominant corals and coralline algae relative to wave energy and sea level rise. Moderate wave energy favors vertically rapid growth that is porous and uncemented; high wave energy favors slow but compact growth. Growth potentials of Caribbean and Indo-Pacific reefs are probably equivalent. Major differences are probably not due to biological or direct climatic factors but are in part related to differing patterns of sea level rise resulting from Holocene crustal adjustment. The nature and position of antecedent foundations developed by high interglacial and interstadial sea levels is especially critical and is largely controlled by regional tectonic factors, especially long-term subsidence. 相似文献
17.
A magnitude 7.2 earthquake in 1975 caused the south flank of Kilauea Volcano, Hawaii, to move seaward in response to slippage along a deep fault. Since then, a large part of the volcano's edifice has been adjusting to this perturbation. The summit of Kilauea extended at a rate of 0.26 meter per year until 1983, the south flank uplifted more than 0.5 meter, and the axes of both the volcano's rift zones extended and subsided; the summit continues to subside. These ground-surface motions have been remarkably steady and much more widespread than those caused by either recurrent inflation and deflation of the summit magma chamber or the episodic propagation of dikes into the rift zones. Kilauea's magmatic system is, therefore, probably deeper and more extensive than previously thought; the summit and both rift zones may be underlain by a thick, near vertical dike-like magma system at a depth of 3 to 9 kilometers. 相似文献
18.
Newell ND 《Science (New York, N.Y.)》1960,132(3420):144-145
Geological studies in the western Atlantic indicate that sea level is now near its highest position since the Pleistocene, and that intertidal erosion at this level has been negligible. The evidence conflicts with the idea that many coral reefs were recently planed down from a higher stand of the sea. 相似文献
19.
Anthropogenic increases of atmospheric carbon dioxide lead to warmer sea surface temperatures and altered ocean chemistry. Experimental evidence suggests that coral calcification decreases as aragonite saturation drops but increases as temperatures rise toward thresholds optimal for coral growth. In situ studies have documented alarming recent declines in calcification rates on several tropical coral reef ecosystems. We show there is no widespread pattern of consistent decline in calcification rates of massive Porites during the 20th century on reefs spanning an 11° latitudinal range in the southeast Indian Ocean off Western Australia. Increasing calcification rates on the high-latitude reefs contrast with the downward trajectory reported for corals on Australia's Great Barrier Reef and provide additional evidence that recent changes in coral calcification are responses to temperature rather than ocean acidification. 相似文献
20.
Nerem RS 《Science (New York, N.Y.)》1995,268(5211):708-710
The TOPEX/POSEIDON satellite altimeter mission has measured global mean sea level every 10 days over the last 2 years with a precision of 4 millimeters, which approaches the requirements for climate change research. The estimated rate of sea level change is +3.9 +/- 0.8 millimeters per year. A substantial portion of this trend may represent a short-term variation unrelated to the long-term signal expected from global warming. For this reason, and because the long-term measurement accuracy requires additional monitoring, a longer time series is necessary before climate change signals can be unequivocally detected. 相似文献