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  • Bay of Bengal  (2)
  • GIK/IfG; GIK16160-3; Gravity corer (Kiel type); Institute for Geosciences, Christian Albrechts University, Kiel; M75/3; M75/3_137-3; Meteor (1986); Sambesi Fan; SL  (2)
  • 031-1; Alkenones; GC; Gravity corer; Labrador Sea; Maria S. Merian; Mg/Ca paleothermometry; MSM45; MSM45_431-1; Stable isotopes  (1)
  • 161-977A; AGE; Alboran Sea; DEPTH, sediment/rock; DRILL; Drilling/drill rig; Gulf of Cadiz; Heinrich Stadials; Joides Resolution; Leg161; Mediterranean overflow; millennial climate change; sapropels; Stable isotopes; δ18O, seawater, reconstructed  (1)
Document type
Keywords
Publisher
Language
Years
  • 1
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    Variability of the Indian Monsoon in the Andaman Sea Across the Miocene-Pliocene Transition (2021)
    Details
    Publication Date: 2021-10-07
    Description: We reconstructed the variability of the Earth's strongest hydrological system, the Indian monsoon, over the interval 6.24 to 4.91 Ma at International Ocean Discovery Program (IODP) Expedition 353 Site U1448 in the Andaman Sea. We integrated high-resolution benthic and planktic foraminiferal carbon and oxygen isotopes with Mg/Ca measurements of the mixed layer foraminifer Trilobatus sacculifer to reconstruct the isotopic composition of seawater (δ18Osw) and the gradient between planktic and benthic foraminiferal δ13C. A prominent increase in mixed layer temperatures of ~4°C occurred between 5.55 and 5.28 Ma, accompanied by a change from precession- to obliquity-driven variability in planktic δ18O and δ18Osw. We suggest that an intensified cross-equatorial transport of heat and moisture, paced by obliquity, led to increased summer monsoon precipitation during warm stages after 5.55 Ma. Transient cold stages were characterized by reduced mixed layer temperatures and summer monsoon failure, thus resembling late Pleistocene stadials. In contrast, an overall cooler background climate state with a strengthened biological pump prevailed prior to 5.55 Ma. These findings highlight the importance of internal feedback processes for the long-term evolution of the Indian monsoon.
    Keywords: 551.6 ; Indian monsoon ; Miocene-Pliocene transition ; Bay of Bengal ; Mg/Ca paleothermometry ; stable isotopes ; orbital forcing
    Language: English
    Type: map
    Location Call Number Limitation Availability
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    CITATION GEO-LEO
  • 2
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    An ~130 kyr Record of Surface Water Temperature and δ18O From the Northern Bay of Bengal: Investigating the Linkage Between Heinrich Events and Weak Monsoon Intervals in Asia (2021)
    Details
    Publication Date: 2021-10-15
    Description: Millennial-scale reductions in monsoon precipitation, so-called Weak Monsoon Intervals (WMIs), have been identified in numerous paleoclimate records across the Afro-Asian monsoon domain throughout the last glacial-interglacial cycle. These are considered the regional response to cooling during Heinrich events in the North Atlantic realm and several mechanisms have been suggested to explain this hemisphere-scale climatic teleconnection. In particular, reductions in Indian Ocean sea surface temperature (SST) have been proposed as the linking element between Heinrich events and WMIs. However, the validity of this relationship has only been demonstrated for the last ~20 kyr, leaving unresolved whether it also holds on longer time scales. Here we present a new paired record of planktonic foraminifera-based δ18Osw-ivc and UK'37-based SST from the northern Bay of Bengal, covering the last ~130 kyr. The δ18Osw-ivc record clearly reflects orbitally paced changes of Indian Summer Monsoon intensity superimposed by centennial- to millennial-scale WMIs that occurred synchronously to North Atlantic Heinrich events. Comparison with the UK'37-based SST reconstruction reveals, however, that WMIs in most cases were not paralleled by ocean surface cooling, questioning whether Indian Ocean SST lowering was the linking element between Heinrich events and reductions in monsoon precipitation in Asia also during the last glacial period.
    Keywords: 551 ; Indian Summer Monsoon ; Weak Monsoon Intervals ; marine sediments ; Bay of Bengal ; foraminifera oxygen isotopes ; UK'37 sea surface temperature
    Language: English
    Type: map
    Location Call Number Limitation Availability
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    CITATION GEO-LEO
  • 3
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    δ¹⁸O reconstruction of seawater from Termination II of ODP Hole 161-977A (2020)
    PANGAEA
    Details
    Publication Date: 2023-12-20
    Keywords: 161-977A; AGE; Alboran Sea; DEPTH, sediment/rock; DRILL; Drilling/drill rig; Gulf of Cadiz; Heinrich Stadials; Joides Resolution; Leg161; Mediterranean overflow; millennial climate change; sapropels; Stable isotopes; δ18O, seawater, reconstructed
    Type: Dataset
    Format: text/tab-separated-values, 59 data points
    Location Call Number Limitation Availability
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    DATA PANGAEA
  • 4
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    Stable hydrogen and carbon isotope records and concentration data for four long chain n-alkanes from core GIK16160-3 derived from the Zambezi delta in the Mozambique Channel during the last 37,000 years (2013)
    PANGAEA
    In:  Supplement to: Wang, Yiming V; Larsen, Thomas; Leduc, Guillaume; Andersen, Nils; Blanz, Thomas; Schneider, Ralph R (2013): What does leaf wax dD from a mixed C3/C4 vegetation region tell us? Geochimica et Cosmochimica Acta, 111, 128-139, https://doi.org/10.1016/j.gca.2012.10.016
    Details
    Publication Date: 2024-02-03
    Description: Hydrogen isotope values (dD) of sedimentary terrestrial leaf wax such as n-alkanes or n-acids have been used to map and understand past changes in rainfall amount in the tropics because dD of precipitation is commonly assumed as the first order controlling factor of leaf wax dD. Plant functional types and their photosynthetic pathways can also affect leaf wax dD but these biological effects are rarely taken into account in paleo studies relying on this rainfall proxy. To investigate how biological effects may influence dD values we here present a 37,000-year old record of dD and stable carbon isotopes (d13C) measured on four n-alkanes (n-C27, n-C29, n-C31, n-C33) from a marine sediment core collected off the Zambezi River mouth. Our paleo d13C records suggest that each individual n-alkanes had different C3/C4 proportional contributions. n-C29 was mostly derived from a C3 dicots (trees, shrubs and forbs) dominant vegetation throughout the entire record. In contrast, the longer chain n-C33 and n-C31 were mostly contributed by C4 grasses during the Glacial period but shifted to a mixture of C4 grasses and C3 dicots during the Holocene. Strong correlations between dD and d13C values of n-C33 (correlation coefficient R2 = 0.75, n = 58) and n-C31 (R2 = 0.48, n = 58) suggest that their dD values were strongly influenced by changes in the relative contributions of C3/C4 plant types in contrast to n-C29 (R2 = 0.07, n = 58). Within regions with variable C3/C4 input, we conclude that dD values of n-C29 are the most reliable and unbiased indicator for past changes in rainfall, and that dD and d13C values of n-C31 and n-C33 are sensitive to C3/C4 vegetation changes. Our results demonstrate that a robust interpretation of palaeohydrological data using n-alkane dD requires additional knowledge of regional vegetation changes from which nalkanes are synthesized, and that the combination of dD and d13C values of multiple n-alkanes can help to differentiate biological effects from those related to the hydrological cycle.
    Keywords: GIK/IfG; GIK16160-3; Gravity corer (Kiel type); Institute for Geosciences, Christian Albrechts University, Kiel; M75/3; M75/3_137-3; Meteor (1986); Sambesi Fan; SL
    Type: Dataset
    Format: application/zip, 2 datasets
    Location Call Number Limitation Availability
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    DATA PANGAEA
  • 5
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    Paleotemperature reconstructions on sediment core GIK161603-3 (2013)
    PANGAEA
    In:  Supplement to: Wang, Yiming V; Leduc, Guillaume; Regenberg, Marcus; Andersen, Nils; Larsen, Thomas; Blanz, Thomas; Schneider, Ralph R (2013): Northern and southern hemisphere controls on seasonal sea surface temperatures in the Indian Ocean during the last deglaciation. Paleoceanography, 28(4), 619-632, https://doi.org/10.1002/palo.20053
    Details
    Publication Date: 2024-02-03
    Description: Different proxies for sea surface temperature (SST) often exhibit divergent trends for deglacial warming in tropical regions, hampering our understanding of the phase relationship between tropical SSTs and continental ice volume at glacial terminations. To reconcile divergent SST trends, we report reconstructions of two commonly used paleothermometers (the foraminifera G. ruber Mg/Ca and the alkenone unsaturation index) from a marine sediment core collected in the southwestern tropical Indian Ocean encompassing the last 37,000 years. Our results show that SSTs derived from the alkenone unsaturation index (UK'37) are consistently warmer than those derived from Mg/Ca by ~2-3°C except for the Heinrich Event 1. In addition, the initial timing for the deglacial warming of alkenone SST started at ~15.6 ka, which lags behind that of Mg/Ca temperatures by 2.5 kyr. We argue that the discrepancy between the two SST proxies reflects seasonal differences between summer and winter rather than post-depositional processes or sedimentary biases. The UK'37 SST record clearly mimics the deglacial SST trend recorded in the North Atlantic region for the earlier part of the termination, indicating the early deglacial warming trend attributed to local summer temperatures was likely mediated by changes in the Atlantic Meridional Overturning Circulation at the onset of the deglaciation, In contrast, the glacial to interglacial SST pattern recorded by G. ruber Mg/Ca probably reflects cold season SSTs. This indicates that the cold season SSTs was likely mediated by climate changes in the southern hemisphere, as it closely tracks the Antarctic timing of deglaciation. Therefore our study reveals that the tropical southwestern Indian Ocean seasonal SST was closely linked to climate changes occurring in both hemispheres. The austral summer and winter recorded by each proxy is further supported with seasonal SST trends modeled by AOGCMs for our core site. Our interpretation that the alkenone and Mg/Ca SSTs are seasonally biased may also explain similar proxy mismatches observed in other tropical regions at the onset of the last termination.
    Keywords: GIK/IfG; GIK16160-3; Gravity corer (Kiel type); Institute for Geosciences, Christian Albrechts University, Kiel; M75/3; M75/3_137-3; Meteor (1986); Sambesi Fan; SL
    Type: Dataset
    Format: application/zip, 3 datasets
    Location Call Number Limitation Availability
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    DATA PANGAEA
  • 6
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    Age model, alkenones and stable isotopes of sediment core MSM45-31-1 (MSM45_431-1) (2019)
    PANGAEA
    In:  Supplement to: Lochte, Annalena Antonia; Schneider, Ralph R; Kienast, Markus; Repschläger, Janne; Blanz, Thomas; Garbe-Schönberg, Dieter; Andersen, Nils (2020): Surface and subsurface Labrador Shelf water mass conditions during the last 6000 years. Climate of the Past, 16(4), 1127-1143, https://doi.org/10.5194/cp-16-1127-2020
    Details
    Publication Date: 2024-02-02
    Description: The Labrador Sea is important for the modern global thermohaline circulation system through the formation of intermediate Labrador Sea Water (LSW) that has been hypothesized to stabilize the modern mode of North Atlantic deep-water circulation. The rate of LSW formation is controlled by the amount of winter heat loss to the atmosphere, the expanse of freshwater in the convection region and the inflow of saline waters from the Atlantic. The Labrador Sea, today, receives freshwater through the East and West Greenland Currents (EGC, WGC) and the Labrador Current (LC). Several studies have suggested the WGC to be the main supplier of freshwater to the Labrador Sea, but the role of the southward flowing LC in Labrador Sea convection is still debated. At the same time, many paleoceanographic reconstructions from the Labrador Shelf focussed on late Deglacial to early Holocene meltwater run-off from the Laurentide Ice Sheet (LIS), whereas little information exists about LC variability since the final melting of the LIS about 7,000 years ago. In order to enable better assessment of the role of the LC in deep-water formation and its importance for Holocene climate variability in Atlantic Canada, this study presents high-resolution middle to late Holocene records of sea surface and bottom water temperatures, freshening and sea ice cover on the Labrador Shelf during the last 6,000 years. Our records reveal that the LC underwent three major oceanographic phases from the Mid- to Late Holocene. From 6.2 to 5.6 ka BP, the LC experienced a cold episode that was followed by warmer conditions between 5.6 and 2.1 ka BP, possibly associated with the late Holocene Thermal Maximum. Although surface waters on the Labrador Shelf cooled gradually after 3 ka BP in response to the Neoglaciation, Labrador Shelf subsurface/bottom waters show a shift to warmer temperatures after 2.1 ka BP. Although such an inverse stratification by cooling of surface and warming of subsurface waters on the Labrador Shelf would suggest a diminished convection during the last two millennia compared to the mid-Holocene, it remains difficult to assess whether hydrographic conditions in the LC have had a significant impact on Labrador Sea deep-water formation.
    Keywords: 031-1; Alkenones; GC; Gravity corer; Labrador Sea; Maria S. Merian; Mg/Ca paleothermometry; MSM45; MSM45_431-1; Stable isotopes
    Type: Dataset
    Format: application/zip, 3 datasets
    Location Call Number Limitation Availability
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    DATA PANGAEA
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