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| Kender, Sev; Mcclymont, Erin L.; Elmore, Aurora C.; Emanuele, Dario; Leng, Melanie J.; Elderfield, Henry. |
| Understanding the interaction between climate and biotic evolution is crucial for deciphering the sensitivity of life. An enigmatic mass extinction occurred in the deep oceans during the Mid Pleistocene, with a loss of over 100 species (20%) of sea floor calcareous foraminifera. An evolutionarily conservative group, benthic foraminifera often comprise 450% of eukaryote biomass on the deep-ocean floor. Here we test extinction hypotheses (temperature, corrosiveness and productivity) in the Tasman Sea, using geochemistry and micropalaeontology, and find evidence from several globally distributed sites that the extinction was caused by a change in phytoplankton food source. Coccolithophore evolution may have enhanced the seasonal 'bloom' nature of primary... |
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| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00496/60723/65259.pdf |
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| Bachem, Paul E.; Risebrobakken, Bjorg; De Schepper, Stijn; Mcclymont, Erin L.. |
| The Pliocene was a time of global warmth with small sporadic glaciations, which transitioned towards the larger-scale Pleistocene glacial-interglacial variability. Here, we present high-resolution records of sea surface temperature (SST) and ice-rafted debris (IRD) in the Norwegian Sea from 5.32 to 3.14 Ma, providing evidence that the Pliocene surface conditions of the Norwegian Sea underwent a series of transitions in response to orbital forcing and gateway changes. Average SSTs are 2 degrees C above the regional Holocene mean, with notable variability on millennial to orbital timescales. Both gradual changes and threshold effects are proposed for the progression of regional climate towards the Late Pliocene intensification of Northern Hemisphere... |
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| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00495/60710/65332.pdf |
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| Pichevin, Laetitia; Ganeshram, Raja S.; Reynolds, Ben C.; Prahl, Fredrick; Pedersen, Thomas F.; Thunell, Robert; Mcclymont, Erin L.. |
| Iron is considered to play a large role in the cycling of Si in Fe-limited regions of the ocean, but little is known about its role in Si biogeochemistry outside these areas. Here, we present published sediment trap data, new nutrient profiles and high resolution sedimentary records (Si isotopes, Biogenic silica%, N% and C%) from the Gulf of California, a non-Fe-limited region, to investigate the history of Si cycling in this highly productive basin. Modern nutrient profiles show that silicic acid in subsurface waters is in excess relative to nitrate and is therefore incompletely utilized during moderate winter upwelling events. Modern data, however, suggest that during intense upwelling episodes, silicic acid is preferentially utilized relative to nitrate... |
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| Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00265/37665/36967.pdf |
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| Mcclymont, Erin L.; Ganeshram, Raja S.; Pichevin, Laetitia; Talbot, Helen M.; Van Dongen, Bart E.; Thunell, Robert C.; Haywood, Alan M.; Singarayer, Joy S.; Valdes, Paul J.. |
| Centennial-scale records of sea-surface temperature and opal composition spanning the Last Glacial Maximum and Termination 1 (circa 25-6 ka) are presented here from Guaymas Basin in the Gulf of California. Through the application of two organic geochemistry proxies, the U-37(K') index and the TEX86H index, we present evidence for rapid, stepped changes in temperatures during deglaciation. These occur in both temperature proxies at 13 ka (similar to 3 degrees C increase in 270 years), 10.0 ka (similar to 2 degrees C decrease over similar to 250 years) and at 8.2 ka (3 degrees C increase in <200 years). An additional rapid warming step is also observed in TEX86H at 11.5 ka. In comparing the two temperature proxies and opal content, we consider the... |
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| Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00265/37664/36972.pdf |
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| Mcclymont, Erin L.; Sosdian, Sindia M.; Rosell-mele, Antoni; Rosenthal, Yair. |
| mid-Pleistocene climate transition (MPT) is defined by the emergence of high amplitude, quasi-100 ka glacial-interglacial cycles from a prior regime of more subtle 41 ka cycles. This change in periodicity and amplitude cannot be explained by a change in 'external' astronomical forcing. Here, we review and integrate published records of sea-surface temperatures (SSTs) to assess whether a common global expression of the MPT in the surface ocean can be recognized, and examine our findings in light of mechanisms proposed to explain climate system reorganization across the MPT. We show that glacial-interglacial variability in SSTs is superimposed upon a longer-term cooling trend in oceanographic systems spanning the low-to high-latitudes. Regional variability... |
| Tipo: Text |
Palavras-chave: Sea surface temperatures; Mid-Pleistocene transition; Ice sheets; 100 kyr world. |
| Ano: 2013 |
URL: https://archimer.ifremer.fr/doc/00264/37510/82770.pdf |
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| Bachem, Paul E.; Risebrobakken, Bjorg; Mcclymont, Erin L.. |
| The mid-Piacenzian warm period (3.264-3.025 Ma) of the Pliocene epoch has been proposed as a possible reference for future warm climate states. However, there is significant disagreement over the magnitude of high latitude warming between data and models for this period of time, raising questions about the driving mechanisms and responsible feedbacks. We have developed a new set of orbital-resolution alkenone-based sea surface temperature (SST) and ice rafted debris (IRD) records from the Norwegian Sea spanning 3.264-3.14 Ma. The SSTs in the Norwegian Sea were 2-3 degrees C warmer than the Holocene average, likely caused by the radiative effect of higher atmospheric CO2 concentrations. There is notable obliquity-driven SST variability with a range of 4... |
| Tipo: Text |
Palavras-chave: Pliocene; Norwegian Sea; ODP Site 642; Alkenones; SST; Subpolar gyre. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00421/53230/83372.pdf |
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| Petrick, Benjamin F.; Mcclymont, Erin L.; Marret, Fabienne; Van Der Meer, Marcel T. J.. |
| The Southeast Atlantic Ocean is an important component of global ocean circulation, as it includes heat and salt transfer into the Atlantic through the Agulhas leakage as well as the highly productive Benguela upwelling system. Here we reconstruct sea surface temperatures (SSTs) from Ocean Drilling Program (ODP) Site 1087 in the Southeast Atlantic to investigate surface ocean circulation patterns during the late Pleistocene (0-500 ka). The U-37(K)' index and dinoflagellate cyst assemblages are used to reconstruct SSTs, delta D-alkenone is used to reconstruct changes in sea surface salinity, and mass accumulation rates of alkenones and chlorine pigments are quantified to detect changing marine export productivity. The greatest amplitude of SST warming... |
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| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00351/46242/46108.pdf |
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| Caley, Thibaut; Extier, Thomas; Collins, James A.; Schefuss, Enno; Dupont, Lydie; Malaize, Bruno; Rossignol, Linda; Souron, Antoine; Mcclymont, Erin L.; Jimenez-espejo, Francisco J.; Garcia-comas, Carmen; Eynaud, Frederique; Martinez, Philippe; Roche, Didier M.; Jorry, Stephan; Charlier, Karine; Wary, Melanie; Gourves, Pierre-yves; Billy, Isabelle; Giraudeau, Jacques. |
| The past two million years of eastern African climate variability is currently poorly constrained, despite interest in understanding its assumed role in early human evolution1,2,3,4. Rare palaeoclimate records from northeastern Africa suggest progressively drier conditions2,5 or a stable hydroclimate6. By contrast, records from Lake Malawi in tropical southeastern Africa reveal a trend of a progressively wetter climate over the past 1.3 million years7,8. The climatic forcings that controlled these past hydrological changes are also a matter of debate. Some studies suggest a dominant local insolation forcing on hydrological changes9,10,11, whereas others infer a potential influence of sea surface temperature changes in the Indian Ocean8,12,13. Here we show... |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00449/56059/57581.pdf |
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| Risebrobakken, Bjorg; Andersson, Carin; De Schepper, Stijn; Mcclymont, Erin L.. |
| The Pliocene (5.3-2.6Ma) is often described as a relatively stable climatic period, with warm temperatures characterizing high latitudes. New suborbital resolved stable isotope records from Ocean Drilling Program Hole 642B in the eastern Nordic Seas document that the Pliocene was not a stable period characterized by one climate. Rather, seven distinct climate phases, each lasting between 150,000 and 400,000years, are identified and characterized in the time interval 5.1-3.1Ma. Four of the transitions between the defined climate phases occurred close to an eccentricity minimum and a minimum in amplitude of change for Northern Hemisphere summer insolation, while two occurred around an eccentricity maximum and a maximum in amplitude in insolation change.... |
| Tipo: Text |
Palavras-chave: Pliocene; Nordic Seas; Stable isotopes; Diagenetic calcite; Paleogeography; External and internal forcing. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00504/61599/65864.pdf |
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