Multi-proxy Coral Reconstruction of Holocene Climate and Reef Growth in the Eastern Indian Ocean PDF Download

Author: Nerilie Jane Abram
Publisher:
ISBN:
Category : Climatic changes
Languages : en
Pages : 262

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Author: Lauren Trent Toth
Publisher:
ISBN:
Category :
Languages : en
Pages : 804

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In recent decades, a variety of local- to global-scale disturbances have caused the global degradation of coral-reef ecosystems. In most regions, large-scale coral mortality is a recent phenomenon. In contrast, my records from the tropical eastern Pacific (TEP) have revealed a period of limited coral-reef development, beginning about 4000 cal BP (calibrated calendar years before 1950), which lasted for the next 2500 years. This protracted hiatus in reef growth provides the opportunity to test explicit predictions about the causes of reef collapse, the controls on reef resilience, and the likely trajectories of reef development in the future. Reefs of the TEP are subject to a variety of modern environmental stressors, the most important of which are seasonal upwelling and interannual impacts of the El Niño-Southern Oscillation (ENSO); however, the relative roles of these stressors in shaping past reef development are unknown. Although it is generally accepted that reef growth in the TEP is slow compared with other regions around the world, this assumption has never been tested, and the paleoecological record from reefs in this region is limited. Using data from cores of reef frameworks collected throughout Pacific Panamá, this study evaluated trends in reef development from ~7000 cal BP to the present to assess the impacts of environmental variability on reef growth during the Holocene. To further characterize the observed hiatus in reef growth and investigate the impact of seasonal upwelling on past reef development, I compared trends in vertical reef accretion among three sites situated along a contemporary gradient of seasonal upwellling: Contadora Island, which received the most intense seasonal upwelling; Iguana Island, where upwelling was moderate; and Canales de Tierra Island, where there was no upwelling. By reconstructing the age of the local radiocarbon reservoir for each of these sites, I confirmed that this general upwelling regime existed from at least ~7000 cal BP to the present. I also used geochemical analyses of fossil coral skeletons and reef sediments from Contadora to reconstruct the regional climatic and oceanographic conditions over the last 7000 years and evaluated their impacts on coral condition. Coral reefs at all three sites stopped growing from ~4100-1600 cal BP, coincident with the shutdown of reef development at several other locations elsewhere in the Pacific. There was a dramatic and significant reduction in reef accretion during the depositional hiatus. Contrary to earlier surmises that reef growth was slow in the TEP, however, millennial rates of reef accretion in Pacific Panama ́before and after the hiatus were similar to those documented in the Caribbean region. There was no significant difference in reef accretion among sites, which suggests that although upwelling has an impact on the short-term growth of corals, upwelling does not impact long-term reef accretion. Upwelling did, however, have a significant impact on the duration of reef collapse. The hiatus in reef accretion began earlier, ended later and, therefore, lasted significantly longer at Contadora, where reefs are subject to the strongest seasonal upwelling. Although upwelling was most likely not the ultimate cause of the hiatus, persistent upwelling may reduce the capacity of a reef to recover from major disturbances. Correlative evidence from regional paleoclimate proxies suggested that the ultimate cause of the hiatus was most likely enhanced climatic oscillations, particularly variability associated with ENSO. In the TEP, El Niño and La Niña events result in dramatic changes in sea temperatures, nutrient inputs, turbidity, and sea level, all of which can be problematic for reef development. ENSO activity increased 4500-4000 cal BP, coincident with the onset of the hiatus. Additionally, ENSO variability was likely enhanced from 4000-2000 cal BP due to it becoming in-phase, or "coupled", with the Intertropical Convergence Zone (ITCZ). Overall, hiatus was a time of stronger and more frequent El Niño and La Niña events and this period of enhanced climatic variability likely overwhelmed the capacity of reefs to recover. Reef growth resumed when there was a change in the mode of ENSO, with more El Niño events, but fewer La Niña events after ~2000 cal BP. Climatic reconstructions from this study suggested that oceanic productivity at Contadora was higher in the mid-Holocene, 6000-4000 cal BP, likely as a result of increased upwelling, compared with the period 4000-2000 cal BP. These results supports the conclusion of other researchers that the early to middle Holocene, may have been more "La Niña-like", compared with the late Holocene, when mean climate had shifted to a more "El Niño-like" state. Furthermore, my environmental reconstructions before and after the hiatus in reef accretion reveal that climatic and oceanographic variability in the TEP were greater over centennial scales than previously surmised. From 5000-4500 cal BP, conditions were warmer and drier, and there was less upwelling, than at other times in the Holocene. Oceanic productivity and climatic variability both increased in the 100-200 yr preceding the shutdown of reef growth. These changes are consistent with the hypothesis of escalating ENSO variability overall, and in particular an increase in La Niña activity. I used coral [lower case delta]13C, a measure of productivity and coral health, and B/Ca, a measure of carbonate saturation state within the coral, to track changes in coral condition through time. Dramatic declines in both coral productivity and coral saturation state occurred just before the hiatus, indicating that sublethal declines in coral health could serve as early warning signs of ecosystem collapse. Although coral productivity was high just after the hiatus, it gradually declined over the period ~1500 cal BP to present. One explanation for the deteriorating health of corals during this interval was that the increase in the number of El Niño events through the late Holocene resulted in an increasing frequency and severity of coral bleaching events. The parallel between the reduction in coral productivity before the collapse of Panamanian reefs ~4100 cal BP and the slow decline of coral productivity through the late Holocene may indicate that reefs in the TEP are headed toward another significant interruption in reef development in the future. There is no clear consensus on how anthropogenic climate change will affect ENSO in the future; however, many of the same conditions that occurred during the hiatus are also expected under reasonable scenarios of future climate change. If the history of reef development in Pacific Panamá is any indication of what may happen in the future, climate change could indeed be pushing some Pacific reefs towards another major collapse. On the other hand, these reefs were able to recover after a 2500-yr hiatus in reef development. Thus, if the current trajectories of climate change can be reversed, there may yet be hope for the reefs of the future.

Author: National Research Council
Publisher: National Academies Press
ISBN: 0309102251
Category : Science
Languages : en
Pages : 160

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In response to a request from Congress, Surface Temperature Reconstructions for the Last 2,000 Years assesses the state of scientific efforts to reconstruct surface temperature records for Earth during approximately the last 2,000 years and the implications of these efforts for our understanding of global climate change. Because widespread, reliable temperature records are available only for the last 150 years, scientists estimate temperatures in the more distant past by analyzing "proxy evidence," which includes tree rings, corals, ocean and lake sediments, cave deposits, ice cores, boreholes, and glaciers. Starting in the late 1990s, scientists began using sophisticated methods to combine proxy evidence from many different locations in an effort to estimate surface temperature changes during the last few hundred to few thousand years. This book is an important resource in helping to understand the intricacies of global climate change.

Author: Peter W. Glynn
Publisher: Univ of California Press
ISBN: 9780520047136
Category : Nature
Languages : en
Pages : 354

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00 This scientifically thorough,lucidly written work explores the nature, development, and extent of the archipelago's reef-building corals. Also included is an annotated list of the Scleractianian Corals by John W. Wells This scientifically thorough,lucidly written work explores the nature, development, and extent of the archipelago's reef-building corals. Also included is an annotated list of the Scleractianian Corals by John W. Wells

Author: Jonathan Turnbull Phinney
Publisher: American Geophysical Union
ISBN: 0875903592
Category : Science
Languages : en
Pages : 251

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Published by the American Geophysical Union as part of the Coastal and Estuarine Studies, Volume 61. The effects of increased atmospheric carbon dioxide and related climate change on shallow coral reefs are gaining considerable attention for scientific and economic reasons worldwide. Although increased scientific research has improved our understanding of the response of coral reefs to climate change, we still lack key information that can help guide reef management. Research and monitoring of coral reef ecosystems over the past few decades have documented two major threats related to increasing concentrations of atmospheric CO2: (1) increased sea surface temperatures and (2) increased seawater acidity (lower pH). Higher atmospheric CO2 levels have resulted in rising sea surface temperatures and proven to be an acute threat to corals and other reef-dwelling organisms. Short periods (days) of elevated sea surface temperatures by as little as 1–2°C above the normal maximum temperature has led to more frequent and more widespread episodes of coral bleaching-the expulsion of symbiotic algae. A more chronic consequence of increasing atmospheric CO2 is the lowering of pH of surface waters, which affects the rate at which corals and other reef organisms secrete and build their calcium carbonate skeletons. Average pH of the surface ocean has already decreased by an estimated 0.1 unit since preindustrial times, and will continue to decline in concert with rising atmospheric CO2. These climate-related Stressors combined with other direct anthropogenic assaults, such as overfishing and pollution, weaken reef organisms and increase their susceptibility to disease.

Author: Gerold Wefer
Publisher: Springer Science & Business Media
ISBN: 3642558623
Category : Science
Languages : en
Pages : 320

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Europe is a continent with a high coast-to-surface ratio, and European seas encompass a broad range of settings and regimes. The sustainable development of living and non-living marine resources, the protection of the marine environment and the provision of marine-based services are critical to economic prosperity and to the quality of life of European citizens. Addressing these concerns, marine-science researchers conducted a workshop reviewing major topics of European marine research. This publication contains overview and thematic background papers, as well as reports and recommendations for future research covering topics such as ocean-climate coupling, biogeochemistry, coastal and shelf processes, and ecosystem functioning/biodiversity.

Author: Christopher Matthew Kovalik
Publisher:
ISBN:
Category :
Languages : en
Pages : 128

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The full effects of climate change are still unknown, but the future of coral-reefs appears bleak. Recently, there have been major episodes of coral bleaching and coral disease around the world. The recent loss of coral has been extreme, but there is some precedent for coral-reef collapse in the geologic record; several millennial-scale hiatuses in reef growth have been found throughout the Pacific Ocean in the late Holocene. A ~2,500-year hiatus in reef growth was found at multiple sites in Pacific Panamá, Costa Rica, Australia and Hawaii, as well as several small-scale hiatuses in the northern Ryukyu Islands. I used push-coring to compare the Holocene histories of two sites on opposite sides of the Pacific Ocean to see if they experienced this same millennial-scale hiatus in reef growth. The first site was Coiba Island, Panamá. This site has some of the oldest and thickest reefs in the eastern Pacific, in part due to its relatively stable year-round sea-surface temperatures. Coiba is not affected by tropical cyclones, as they move westward across the Pacific. The second coring site was Kumejima, Japan. Kumejima is bathed by the warm waters of the Kuroshio Current. Kumejima is part of the Ryukyu Island Arc, which is highly exposed to storm activity, experiencing numerous tropical cyclones annually. The climatic conditions at each site were examined through wavelet analysis. Wavelet analysis of sea-surface temperature anomalies, using monthly data from 1870-2012, was undertaken for each site, highlighting the periodicity and timing of trends in anomalous temperatures. These records were then compared with each other using wavelet-coherence analysis. Wavelet-coherence analysis revealed correlations between the two wavelets, highlighting the periodicity and time period when these sites were experiencing similar anomalous temperatures. Using two different forms of wavelet coherence, it was shown that these sites experienced anomalous temperatures at the ENSO (El Niño/Southern Oscillation) timescale only periodically throughout the past century and a half. There was also visible correlation at the decadal timescale twice, likely reflecting the Pacific Decadal Oscillation. Wavelet analysis made shared climatic trends between these sites much easier to detect and also revealed that these two dissimilar sites are linked climatically. Using cores taken from coral-reef framework to assess coral growth of the past ~6000 cal BP (calibrated calendar years before 1950), a hiatus in reef growth was found from ~4290-2024 cal BP at Coiba. Even with some of the best conditions for coral growth in the eastern Pacific, Coiba Island also experienced this millennial-scale hiatus in reef growth. The hiatus found at Coiba occurred contemporaneously with the millennial-scale hiatuses in reef growth observed in other areas of Pacific Panamá. This hiatus in reef growth took place during a time of increased ENSO activity; a similar increase in ENSO activity is predicted under future climate-change conditions. Extreme El Niño and extreme La Niña events are predicted to increase with climate change, threatening the precious coral-reef ecosystem that is already sparse in the equatorial eastern Pacific. Nearly all corals in the cores analyzed from Kumejima were in very poor taphonomic condition and were comprised nearly entirely of Acropora spp. encrusted in coralline algae. Radiocarbon ages from the Kumejima cores revealed a mixed deposition. All dates collected from depths ranging from 30-235 cm below the surface were between the ages of 2966-3775 cal BP. All of these corals dated within the time frame of the hiatus observed in Panamá, showing that there was coral growth at Kumejima during this time. The dates obtained from coral from Kumejima were also during the short-term hiatus found at nearby Kodakarajima, in the Northern Ryukyus, meaning the hiatus at Kodakarajima was likely a localized event. Every coral dated from Kumejima was alive during the Pulleniatina Minimum Event (PME), which is believed to have resulted in the slowing of the Kuroshio Current. Any alteration in the flow of the Kuroshio could have altered reef growth at Kumejima: my record from this site may represent rubble deposits during this event. Both of these sites are largely controlled by oceanic-atmospheric processes taking place on a large scale. Reef dynamics at Coiba Island were likely controlled by ENSO activity, especially Eastern Pacific El Niño, and this site has low coral diversity. On the other hand, reef development at Kumejima is influenced by storm activity, mainly tropical cyclones, which, in both frequency and intensity, can be attributed to the same forces controlling ENSO activity in the eastern equatorial Pacific. With the current projections of climate change the oceanic waters will warm, storm intensity will increase, ENSO events will become more extreme, and patterns of precipitation will likely change. Similar changes have occurred in the past, driving corals beyond their threshold of survival. The prediction of a more El Niño-like conditions in the future could be disastrous for both Coiba and Kumejima. Coiba would face higher than normal temperatures whereas Kume would experience an increase in the intensity of typhoons. These reefs have been resilient to temperature changes in the past, with Panamanian reefs recovering from an over 2000 year hiatus; if we can slow or reverse the current rate of climate change in the immediate future, these reefs still may stand a chance to survive.

Author: David Hopley
Publisher: Springer Science & Business Media
ISBN: 904812638X
Category : Science
Languages : en
Pages : 1226

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Coral reefs are the largest landforms built by plants and animals. Their study therefore incorporates a wide range of disciplines. This encyclopedia approaches coral reefs from an earth science perspective, concentrating especially on modern reefs. Currently coral reefs are under high stress, most prominently from climate change with changes to water temperature, sea level and ocean acidification particularly damaging. Modern reefs have evolved through the massive environmental changes of the Quaternary with long periods of exposure during glacially lowered sea level periods and short periods of interglacial growth. The entries in this encyclopedia condense the large amount of work carried out since Charles Darwin first attempted to understand reef evolution. Leading authorities from many countries have contributed to the entries covering areas of geology, geography and ecology, providing comprehensive access to the most up-to-date research on the structure, form and processes operating on Quaternary coral reefs.

Author: National Research Council
Publisher: National Academies Press
ISBN: 0309054494
Category : Science
Languages : en
Pages : 645

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This volume reflects the current state of scientific knowledge about natural climate variability on decade-to-century time scales. It covers a wide range of relevant subjects, including the characteristics of the atmosphere and ocean environments as well as the methods used to describe and analyze them, such as proxy data and numerical models. They clearly demonstrate the range, persistence, and magnitude of climate variability as represented by many different indicators. Not only do natural climate variations have important socioeconomic effects, but they must be better understood before possible anthropogenic effects (from greenhouse gas emissions, for instance) can be evaluated. A topical essay introduces each of the disciplines represented, providing the nonscientist with a perspective on the field and linking the papers to the larger issues in climate research. In its conclusions section, the book evaluates progress in the different areas and makes recommendations for the direction and conduct of future climate research. This book, while consisting of technical papers, is also accessible to the interested layperson.

Author: James Bowen
Publisher: Springer
ISBN: 3319074792
Category : Science
Languages : en
Pages : 194

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On 4 June 1629, the Batavia, pride of the Dutch East India Company Fleet, was wrecked on her maiden voyage in a seemingly empty expanse of the Indian Ocean. The question “how did this happen?” led to 300 years of investigation by those curious to solve the enigma: what are corals and how are coral reefs formed?. Relying heavily on primary source material Part 1 traces the sequential evolution of scientific thought and practice as the author explores the way this evolution is reflected in the search for understanding corals. At each stage, answers lead to fresh questions that challenge investigators to solve the riddle and new branches of science emerge. Then, with the first enigma finally understood, a new enigma arose. Why are Reefs dying? Part 2 traces the range of problems that have emerged in the past 50 years as marine, ecological, reef and climate scientists attempt to put the pieces of the jigsaw together. Is there a new “canary in the coal mine” warning of the fate of the world as we know it if man’s impact on his environment continues unchecked?.