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  • 1
    Language: English
    In: Earth and Planetary Science Letters, May 15, 2012, Vol.331-332, p.187(14)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.epsl.2012.03.019 Byline: Cyril Giry, Thomas Felis, Martin Kolling, Denis Scholz, Wei Wei, Gerrit Lohmann, Sander Scheffers Keywords: coral Sr/Ca; southern Caribbean climate; sea surface temperature; seasonality; interannual to multidecadal variability; ENSO teleconnection Abstract: Proxy reconstructions of tropical Atlantic sea surface temperature (SST) that extend beyond the period of instrumental observations have primarily focused on centennial to millennial variability rather than on seasonal to multidecadal variability. Here we present monthly-resolved records of Sr/Ca (a proxy of SST) from fossil annually-banded Diploria strigosa corals from Bonaire (southern Caribbean Sea). The individual corals provide time-windows of up to 68years length, and the total number of 295years of record allows for assessing the natural range of seasonal to multidecadal SST variability in the western tropical Atlantic during snapshots of the mid- to late Holocene. Comparable to modern climate, the coral Sr/Ca records reveal that mid- to late Holocene SST was characterised by clear seasonal cycles, persistent quasi-biennial and prominent interannual as well as inter- to multidecadal-scale variability. However, the magnitude of SST variations on these timescales has varied over the last 6.2ka. The coral records show increased seasonality during the mid-Holocene consistent with climate model simulations indicating that southern Caribbean SST seasonality is induced by insolation changes on orbital timescales, whereas internal dynamics of the climate system play an important role on shorter timescales. Interannual SST variability is linked to ocean-atmosphere interactions of Atlantic and Pacific origin. Pronounced interannual variability in the western tropical Atlantic is indicated by a 2.35ka coral, possibly related to a strengthening of the variability of the El Nino/Southern Oscillation throughout the Holocene. Prominent inter- to multidecadal SST variability is evident in the coral records and slightly more pronounced in the mid-Holocene. We finally argue that our coral data provide a target for studying Holocene climate variability on seasonal and interannual to multidecadal timescales, when using further numerical models and high-resolution proxy data. Article History: Received 13 May 2011; Revised 20 December 2011; Accepted 13 March 2012 Article Note: (miscellaneous) Editor: P. DeMenocal
    Keywords: El Nino -- Analysis ; Southern Oscillation -- Analysis ; Corals -- Analysis ; Holocene Paleogeography -- Analysis
    ISSN: 0012-821X
    Source: Cengage Learning, Inc.
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  • 2
    Language: English
    In: Palaeogeography, Palaeoclimatology, Palaeoecology, 2010, Vol.298(3), pp.378-387
    Description: Geochemical tracers incorporated into the skeleton of reef-building corals are ideal proxies for reconstructing environmental parameters of ambient seawater such as temperature and salinity at subseasonal resolution. However, validation concerns of these environmental proxies due to the complex skeleton of some tropical Atlantic corals have hindered such coral-based environmental reconstructions in this region compared to the tropical Pacific. In order to identify complications associated with the complex skeletal architecture of the massive brain coral , we performed microsampling experiments along and across individual skeletal elements. We demonstrate that the mesoscale heterogeneity of Sr/Ca, δ O and δ C is a systematic feature of and is linked to different vital effects between skeletal elements. The thecal wall is significantly depleted in Sr, O and C compared to the adjacent septa and columella and differences between apparent temperature signatures of several degrees are greater for Sr/Ca suggesting that this temperature proxy is more sensitive to skeletal mixing than δ O. Parallel subseasonal microsampling experiments performed along individual skeletal elements of a single corallite of a coral which grew at a rate of 0.65 cm/year allow for investigating potential biases associated with its complex skeletal mesoarchitecture. Highest correlation between Sr/Ca and δ O from skeletal material retrieved from the centre of the thecal wall suggests that microdrilling the theca provides the best environmental signal compared to adjacent microsampling profiles. Moreover, based on monthly-mean climatology, the temperature dependence of Sr/Ca for this profile is comparable to previous calibrations published from faster growing . Based on these results, we conclude that accurate microsampling along the centre of the thecal wall of is a prerequisite for generating robust climate reconstructions from its skeleton.
    Keywords: Coral Records ; Stable Isotopes ; Sr/Ca ; Microsampling ; Diploria Strigosa ; Southern Caribbean Sea ; Geology
    ISSN: 0031-0182
    E-ISSN: 1872-616X
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  • 3
    In: Geophysical Research Letters, 28 July 2018, Vol.45(14), pp.7112-7119
    Description: The climate of the Sahara and Arabian Deserts during the Little Ice Age is not well known, due to a lack of annually resolved natural and documentary archives. We present an annual reconstruction of temperature and aridity derived from Sr/Ca and oxygen isotopes in a coral of the desert‐surrounded northern Red Sea. Our data indicate that the eastern Sahara and Arabian Deserts did not experience pronounced cooling during the late Little Ice Age (~1750–1850) but suggest an even more arid mean climate than in the following ~150 years. The mild temperatures are broadly in line with predominantly negative phases of the North Atlantic Oscillation during the Little Ice Age. The more arid climate is best explained by meridional advection of dry continental air from Eurasia. We find evidence for an abrupt termination of the more arid climate after 1850, coincident with a reorganization of the atmospheric circulation over Europe. The Little Ice Age (~1450–1850) is thought to have been characterized by generally cold conditions in many regions of the globe with little similarities regarding the hydroclimate. The climate of the Sahara and Arabian Deserts during the Little Ice Age is not well known, due to a lack of annually resolved sedimentary, tree ring, speleothem, and documentary archives in these uninhabited arid regions. We present an annual reconstruction of temperature and aridity derived from Sr/Ca and oxygen isotopes in a coral of northern Red Sea, a narrow ocean basin bounded by the eastern Sahara and Arabian Deserts. Our data indicate that these desert areas did not experience pronounced cooling during the late Little Ice Age (~1750–1850) but suggest an even more arid mean climate than today. The mild temperatures and more arid climate are attributed to a changed atmospheric circulation at that time. We find an abrupt termination of the more arid climate after 1850, coincident with a reorganization of the atmospheric circulation over Europe at the end of the Little Ice Age. Our study highlights the need for temperature and aridity reconstructions from the global deserts to detect the full range of climate change over the Common Era. Coral Sr/Ca and oxygen isotope records of the northern Red Sea provide annual reconstructions of temperature and aridity back to 1750 The eastern Sahara‐Arabian Desert region did not experience pronounced cooling during the late Little Ice Age (~1750‐1850) The late Little Ice Age climate of the eastern Sahara‐Arabian Desert was even more arid than today and ended abruptly around 1850
    Keywords: Quaternary Geology ; Africa ; Arabian Peninsula ; Arid Environment ; Asia ; Atmospheric Circulation ; Cenozoic ; Climate ; Europe ; Holocene ; Isotope Ratios ; Isotopes ; Little Ice Age ; Neoglacial ; North Atlantic Oscillation ; O-18/O-16 ; Oxygen ; Paleoclimatology ; Quaternary ; Reconstruction ; Sahara ; Sedimentation ; Solution Features ; Speleothems ; Stable Isotopes ; Terrestrial Environment ; Tree Rings ; Upper Holocene ; Western Europe;
    ISSN: 0094-8276
    E-ISSN: 1944-8007
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  • 4
    Language: English
    In: Earth and Planetary Science Letters, 15 May 2012, Vol.331-332, pp.187-200
    Description: Proxy reconstructions of tropical Atlantic sea surface temperature (SST) that extend beyond the period of instrumental observations have primarily focused on centennial to millennial variability rather than on seasonal to multidecadal variability. Here we present monthly-resolved records of Sr/Ca (a proxy of SST) from fossil annually-banded corals from Bonaire (southern Caribbean Sea). The individual corals provide time-windows of up to 68 years length, and the total number of 295 years of record allows for assessing the natural range of seasonal to multidecadal SST variability in the western tropical Atlantic during snapshots of the mid- to late Holocene. Comparable to modern climate, the coral Sr/Ca records reveal that mid- to late Holocene SST was characterised by clear seasonal cycles, persistent quasi-biennial and prominent interannual as well as inter- to multidecadal-scale variability. However, the magnitude of SST variations on these timescales has varied over the last 6.2 ka. The coral records show increased seasonality during the mid-Holocene consistent with climate model simulations indicating that southern Caribbean SST seasonality is induced by insolation changes on orbital timescales, whereas internal dynamics of the climate system play an important role on shorter timescales. Interannual SST variability is linked to ocean–atmosphere interactions of Atlantic and Pacific origin. Pronounced interannual variability in the western tropical Atlantic is indicated by a 2.35 ka coral, possibly related to a strengthening of the variability of the El Niño/Southern Oscillation throughout the Holocene. Prominent inter- to multidecadal SST variability is evident in the coral records and slightly more pronounced in the mid-Holocene. We finally argue that our coral data provide a target for studying Holocene climate variability on seasonal and interannual to multidecadal timescales, when using further numerical models and high-resolution proxy data. ► Monthly coral Sr/Ca records of tropical Atlantic SST for snapshots of the Holocene. ► ~ 295 yr from decade-long well-distributed time-windows over the last 6.2 ka. ► Proxy-model comparison: orbital control on tropical & North Atlantic SST seasonality. ► Increasing ENSO influence on tropical Atlantic SST variability across the Holocene. ► Inter- to multidecadal SST variability at 6.2 ka in AMO-sensitive region.
    Keywords: Coral Sr/Ca ; Southern Caribbean Climate ; Sea Surface Temperature ; Seasonality ; Interannual to Multidecadal Variability ; Enso Teleconnection ; Geology ; Physics
    ISSN: 0012-821X
    E-ISSN: 1385-013X
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  • 5
    Language: English
    In: Geology, Dec, 2005, Vol.33(12), p.981(4)
    Description: Here we present evidence that the Holocene African monsoon system (AMS) varied in response to the eastern equatorial Atlantic sea-surface temperature (SST). Several short-term episodes of decreased moisture availability as a result of low eastern equatorial Atlantic SST are suggested by planktonic foraminiferal Mg/Ca ratios. These episodes promoted a weakening of the AMS and thus determined the timing and intensity of arid periods. Local sea-surface salinities also reveal regional patterns of precipitation in equatorial western Africa. The high eastern equatorial Atlantic SSTs occur in concert with seasonally increased insolation at low latitudes, suggesting a strong response of African monsoonal precipitation to oceanic conditions at low latitudes. Keywords: eastern equatorial Atlantic, Mg/Ca, sea-surface temperature, African monsoon, aridity, lake levels.
    Keywords: Droughts -- Research ; Droughts -- Africa ; Planktonic Bacteria -- Research
    ISSN: 0091-7613
    E-ISSN: 19432682
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  • 6
    Language: English
    In: Frontiers in Microbiology, March 14, 2017
    Description: Phosphorus is an essential nutrient for all living organisms. In bacteria, the preferential phosphorus source is phosphate, which is often a limiting macronutrient in many areas of the ocean. The geochemical cycle of phosphorus is strongly interconnected with the cycles of other elements and especially iron, because phosphate tends to adsorb onto iron minerals, such as iron oxide formed in oxic marine environments. Although the response to either iron or phosphate limitation has been investigated in several bacterial species, the metabolic interplay between these two nutrients has rarely been considered. In this study we evaluated the impact of phosphate limitation on the iron metabolism of the marine bacterium Pseudovibrio sp. FO-BEG1. We observed that phosphate limitation led to an initial decrease of soluble iron in the culture up to three times higher than under phosphate surplus conditions. Similarly, a decrease in soluble cobalt was more pronounced under phosphate limitation. These data point toward physiological changes induced by phosphate limitation that affect either the cellular surface and therefore the metal adsorption onto it or the cellular metal uptake. We discovered that under phosphate limitation strain FO-BEG1, as well as selected strains of the Roseobacter clade, secreted iron-chelating molecules. This leads to the hypothesis that these bacteria might release such molecules to dissolve iron minerals, such as iron-oxyhydroxide, in order to access the adsorbed phosphate. As the adsorption of phosphate onto iron minerals can significantly decrease phosphate concentrations in the environment, the observed release of iron-chelators might represent an as yet unrecognized link between the biogeochemical cycle of phosphorus and iron, and it suggests another biological function of iron-chelating molecules in addition to metal-scavenging.
    Keywords: Marine Bacteria -- Physiological Aspects ; Iron (Nutrient) -- Physiological Aspects ; Phosphates -- Physiological Aspects
    ISSN: 1664-302X
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  • 7
    Language: English
    In: Sci Rep, 2017, Vol.7(1), pp.15825-15825
    Description: Explanations of the Classic Maya civilization demise on the Yucatán Peninsula during the Terminal Classic Period (TCP; ~CE 750–1050) are controversial. Multiyear droughts are one likely cause, but the role of the Caribbean Sea, the dominant moisture source for Mesoamerica, remains largely unknown. Here we present bimonthly-resolved snapshots of reconstructed sea surface temperature (SST) and salinity (SSS) variability in the southern Caribbean from precisely dated fossil corals. The results indicate pronounced interannual to decadal SST and SSS variability during the TCP, which may be temporally coherent to precipitation anomalies on the Yucatán. Our results are best explained by changed Caribbean SST gradients affecting the Caribbean low-level atmospheric jet with consequences for Mesoamerican precipitation, which are possibly linked to changes in Atlantic Meridional Overturning Circulation strength. Our findings provide a new perspective on the anomalous hydrological changes during the TCP that complement the oft-suggested southward displacement of the Intertropical Convergence Zone. We advocate for a strong role of Caribbean SST and SSS condition changes and related ocean-atmosphere interactions that notably influenced the propagation and transport of precipitation to the Yucatán Peninsula during the TCP.
    Keywords: Biology;
    ISSN: 2045-2322
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  • 8
    In: Paleoceanography, September 2011, Vol.26(3), pp.n/a-n/a
    Description: Mg/Ca ratios of surface and subsurface dwelling foraminifera provide valuable information about the past temperature of the water column. Planktonic foraminifera calcify over a period of weeks to months. Therefore, the range of Mg/Ca temperatures obtained from single specimens potentially records seasonal temperature changes. We present solution‐derived Mg/Ca ratios for single specimens of the planktonic foraminifera species (pink), (white), and from a sediment trap off northwest Africa (20°45.6′N, 18°41.9′W). Cleaning of single specimens was achieved using a flow‐through system in order to prevent sample loss. Mg/Ca ratios of surface dwelling (pink) show strong seasonality linked to sea surface temperature. Mg/Ca ratios of (white) do not show such seasonality. Subsurface dwelling flux is largest during the main upwelling season, but Mg/Ca ratios reflect annual temperatures at intermediate water depths. The sediment trap time series suggests that changes in the range of Mg/Ca ratios exhibited by single specimens of (pink) and from the sedimentary record should provide information on the past temperature range under which these species calcified. Statistical analysis suggests detectable changes in the Mg/Ca range are ≥0.80 mmol/mol ( (pink)) and ≥0.34 mmol/mol (). For (pink), such changes would indicate changes in the seasonal sea surface temperature range 〉4°C or a shift in the main calcification and reproductive period. For , such changes would indicate 〉1.7°C changes in the thermocline temperature or a change in the depth habitat. G. ruber (pink) Mg/Ca ratios exhibit a strong seasonality G. inflata Mg/Ca ratios are remarkably similar throughout the year Mg/Ca range changes 〉0.34–0.80 mmol/mol are indicative of environmental change
    Keywords: Globigerinoides Ruber ; Planktonic Foraminifera ; Seawater Temperature Seasonality ; Single Specimen Mg/Ca
    ISSN: 0883-8305
    E-ISSN: 1944-9186
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  • 9
    In: Nature Communications, 2015, Vol.6
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.gloplacha.2009.10.006 Byline: Thomas Felis (a), Norel Rimbu (b)(c) Keywords: Mediterranean; Middle East; Red Sea; palaeoclimate; North Atlantic Oscillation; corals; oxygen isotopes Abstract: Annually banded reef corals from the northern Red Sea provide a high-resolution archive of past climate variations at the southeastern rim of the Mediterranean basin. Subseasonally resolved oxygen isotope records derived from the carbonate skeletons of these massive colonies robustly document seasonality and interannual to decadal climate variability. These proxy records of climate, supported by analyses of instrumental data and model simulations, reveal the prominent role of the Arctic Oscillation/North Atlantic Oscillation (AO/NAO) in controlling eastern Mediterranean/Middle East climate on seasonal, interannual to decadal and orbital timescales, most pronounced during winter. Variability at interannual periods of 5-6yr evident in the coral records is indicative of AO/NAO-like atmospheric variability over the Northern Hemisphere and its influence on eastern Mediterranean/Middle East climate during the last centuries, the late Holocene and the last interglacial period. The coral oxygen isotope records, which are recording temperature and surface evaporation in the northern Red Sea, are linked via AO/NAO-controlled atmospheric circulation changes to variations in temperature and precipitation throughout the Mediterranean and Middle East region. Whereas the entire eastern Mediterranean/Middle East region experiences colder winters during the high-index state of the AO/NAO, the resulting changes in hydrologic balance have a more complex spatial pattern. More arid conditions in the northern Red Sea are accompanied by drier winters in the northeastern Mediterranean but by wetter winters along the southeastern rim of the Mediterranean Sea. This observation may raise difficulties for proxy-based reconstructions of eastern Mediterranean precipitation from the Levant, which is located in the transition zone between positive and negative precipitation anomalies. Compared to the AO/NAO, the atmospheric teleconnections of the El NiA[+ or -]o-Southern Oscillation (ENSO) on eastern Mediterranean/Middle East climate, which are modulated by higher-latitude atmospheric circulation over the North Pacific-North Atlantic region, are weaker and non-stationary. Author Affiliation: (a) MARUM -- Center for Marine Environmental Sciences, University of Bremen, GEO Building, Klagenfurter Str., 28359 Bremen, Germany (b) Department of Atmospheric Physics, Faculty of Physics, University of Bucharest, Bucharest, Romania (c) Climed Norad, Zeicani 25, Bucharest, Romania Article History: Received 19 January 2009; Accepted 19 October 2009
    Keywords: Rain – Analysis ; Precipitation Variability – Analysis ; Atmospheric Physics – Analysis ; Climate – Analysis ; Atmospheric Circulation – Analysis ; Interglacial Periods – Analysis ; El Nino – Analysis ; Carbonates – Analysis ; Natural Cycles – Analysis;
    ISSN: 2041-1723
    ISSN: 09218181
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  • 10
    In: Paleoceanography and Paleoclimatology, February 2018, Vol.33(2), pp.198-213
    Description: The seasonality of hydroclimate during past periods of warmer than modern global temperatures is a critical component for understanding future climate change scenarios. Although only partially analogous to these scenarios, the last interglacial (LIG, Marine Isotope Stage 5e, ~127–117 ka) is a popular test bed. We present coral δO monthly resolved records from multiple Bonaire (southern Caribbean) fossil corals () that date to between 130 and 118 ka. These records represent up to 37 years and cover a total of 105 years, offering insights into the seasonality and characteristics of LIG tropical Atlantic hydroclimate. Our coral δO records and available coral Sr/Ca‐sea surface temperature (SST) records reveal new insights into the variable relationship between the seasonality of tropical Atlantic seawater δO (δO) and SST. Coral δO seasonality is found to covary with SST and insolation seasonality throughout the LIG, culminating in significantly higher than modern values at 124 and 126 ka. At 124 ka, we reconstruct a 2 month lead of the coral δO versus the Sr/Ca‐SST annual cycle and increased δO seasonality. A fully coupled climate model simulates a concomitant increase of southern Caribbean Sea summer precipitation and depletion of summer δO. LIG hydroclimate at Bonaire differed from today's semiarid climate with a minor rainy season during winter. Cumulatively, our coral δO, δO, and model findings indicate a mid‐LIG northward expansion of the South American Intertropical Convergence Zone into the southern Caribbean Sea, highlighting the importance of regional aspects within model and proxy reconstructions of LIG hydroclimate seasonality. Last interglacial (LIG) coral δ18O records are used to reconstruct tropical Atlantic seawater δ18O (δ18Oseawater) seasonality A 37 year mid‐ last interglacial coral detects higher than modern δ18Oseawater seasonality and a 2 month lead of coral δ18O versus Sr/Ca Mid‐ last interglacial climate model and coral findings indicate an Intertropical Convergence Zone expansion into the South Caribbean Sea
    Keywords: Last Interglacial ; Tropical Atlantic Climate ; Hydroclimate Seasonality ; Coral Seawater Δ 18 O Seasonality ; Intertropical Convergence Zone
    ISSN: 2572-4517
    ISSN: 19449186
    E-ISSN: 2572-4525
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