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| Thornalley, D. J. R.; Blaschek, M.; Davies, F. J.; Praetorius, S.; Oppo, D. W.; Mcmanus, J. F.; Hall, I. R.; Kleiven, H.; Renssen, H.; Mccave, I. N.. |
| The overflow of deep water from the Nordic seas into the North Atlantic plays a critical role in global ocean circulation and climate. Approximately half of this overflow occurs via the Iceland-Scotland (I-S) overflow, yet the history of its strength throughout the Holocene (similar to 0-11 700 yr ago, ka) is poorly constrained, with previous studies presenting apparently contradictory evidence regarding its long-term variability. Here, we provide a comprehensive reconstruction of I-S overflow strength throughout the Holocene using sediment grain size data from a depth transect of 13 cores from the Iceland Basin. Our data are consistent with the hypothesis that the main axis of the I-S overflow on the Iceland slope was shallower during the early Holocene,... |
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| Ano: 2013 |
URL: https://archimer.ifremer.fr/doc/00264/37571/35836.pdf |
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| Channell, J. E. T.; Harrison, R. J.; Lascu, I.; Mccave, I. N.; Hibbert, F. D.; Austin, W. E. N.. |
| Core MD04-2822 from the Rockall Trough has apparent sedimentation rates of ∼ 1 m/kyr during the last deglaciation (Termination I). Component magnetization directions indicate a magnetic excursion at 16.3 m depth in the core, corresponding to an age of 26.5 ka, implying an excursion duration of ∼350 years. Across Termination I, the mean grain size of sortable silt implies reduced bottom-current velocity in the Younger Dryas and Heinrich Stadial (HS)-1A, and increased velocities during the Bølling-Allerød warm period. Standard bulk magnetic parameters imply fining of magnetic grain size from the mid-Younger Dryas (∼12 ka) until ∼ 8 ka. First-order reversal curves (FORCs) were analyzed using ridge extraction to differentiate single domain (SD) from background... |
| Tipo: Text |
Palavras-chave: Magnetic granulometry; FORC-PCA analysis; Sortable silt; Magnetic excursion; Termination I; Rockall Trough. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00333/44456/44128.pdf |
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| Hall, I. R.; Boessenkool, K. P.; Barker, S.; Mccave, I. N.; Elderfield, H.. |
| The subpolar North Atlantic Ocean (SPNA) is of key importance for modulating the climate of NW Europe because of heat loss to the atmosphere from the North Atlantic Current. Although hydrographic properties of the surface SPNA vary on interannual to multidecadal timescales, hydrographic time series scarcely extend back beyond the 1950s. We present a 230 year long record of SPNA surface conditions reconstructed from a very high accumulation rate core that also registers changes in deep flow speed in the Iceland Basin. A lagged correlation is observed between the records of deep flow speed and stable oxygen isotopic composition of the surface SPNA (delta(18)O(w)), with strongest correlation when the paleoflow speed record leads by 15-20 years. This offset... |
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| Ano: 2010 |
URL: https://archimer.ifremer.fr/doc/00231/34203/32762.pdf |
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| Mccave, I. N.; Hall, I. R.. |
| The basis for, and use of, fine grain size parameters for inference of paleoflow speeds is reviewed here. The basis resides in data on deposited sediment taken in conjunction with flow speed measurements in the field, experimental data on suspended sediment transport and deposition, and theoretical treatments of the generation of size distributions of deposits from suspension controlled by particle settling velocity and flow speed. In the deep sea, sorting events occur under resuspension/deposition events in benthic storms. At flow speeds below 10 - 15 cm s(-1), size in the noncohesive "sortable silt'' ( 10 - 63 mm) range is controlled by selective deposition, whereas above that range, removal of finer material by winnowing also plays a role. The best... |
| Tipo: Text |
Palavras-chave: Sortable silt; Grain size; Paleocurrent; Flow speed; Ocean circulation; Contourite; Sediment drift. |
| Ano: 2006 |
URL: https://archimer.ifremer.fr/doc/00234/34515/33417.pdf |
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| Skinner, L.; Mccave, I. N.; Carter, L.; Fallon, S.; Scrivner, A. E.; Primeau, F.. |
| It has been proposed that the ventilation of the deep Pacific carbon pool was not significantly reduced during the last glacial period, posing a problem for canonical theories of glacial-interglacial CO2 change. However, using radiocarbon dates of marine tephra deposited off New Zealand, we show that deep(>2000 m) and shallow sub-surface ocean-atmosphere C-14 age offsets (i.e. 'reservoir-' or 'ventilation' ages) in the southwest Pacific increased by similar to 1089 and 337 yrs respectively, reaching similar to 2689 and similar to 1037 yrs during the late glacial. A comparison with other radiocarbon data from the southern high-latitudes suggests that broadly similar changes were experienced right across the Southern Ocean. If, like today, the Southern... |
| Tipo: Text |
Palavras-chave: Radiocarbon; Ocean ventilation; Carbon cycling; Palaeoceanography. |
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00352/46279/46041.pdf |
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