scholarly journals Tracing the North Atlantic's Bottom Waters

Eos ◽  
2016 ◽  
Author(s):  
Terri Cook
Keyword(s):  
Ocean Circulation ◽  
North Atlantic ◽  
Deep Ocean ◽  
The North ◽  
Nuclear Fuel Reprocessing ◽  
Bottom Waters ◽  
European Nuclear ◽  
Deep Ocean Circulation ◽  
And Behavior ◽  
Fuel Reprocessing

Chemicals released by two European nuclear fuel reprocessing plants, along with certain chlorofluorocarbons, are helping to constrain the speed and behavior of North Atlantic deep-ocean circulation.

scholarly journals The Late Quaternary Sedimentary Record of Reykjanes Ridge, North Atlantic

Radiocarbon ◽  
2001 ◽  
Vol 43 (2B) ◽  
pp. 939-947 ◽  
Author(s):  
M A Prins ◽  
S R Troelstra ◽  
R W Kruk ◽  
K van der Borg ◽  
A F M de Jong ◽  
...  
Keyword(s):  
Grain Size ◽  
Ocean Circulation ◽  
North Atlantic ◽  
Late Quaternary ◽  
Ice Cores ◽  
Deep Ocean ◽  
Reykjanes Ridge ◽  
The North ◽  
The North Atlantic ◽  
Deep Ocean Circulation

Variability in surface and deep ocean circulation in the North Atlantic is inferred from grain-size characteristics and the composition of terrigenous sediments from a deep-sea core taken on Reykjanes Ridge, south of Iceland. End-member modeling of grain size data shows that deep-ocean circulation in this area decreased significantly during periods of maximum iceberg discharge. The episodes of reduced circulation correlate with the cold and abrupt warming phases of the Dansgaard-Oeschger cycles as recognized in the Greenland ice cores.

6. Climate surprises

2021 ◽  
pp. 90-105
Author(s):  
Mark Maslin
Keyword(s):  
Ocean Circulation ◽  
Deep Ocean ◽  
Climate System ◽  
Delayed Response ◽  
Tipping Points ◽  
Threshold Response ◽  
Slowing Down ◽  
The North ◽  
Deep Ocean Circulation ◽  
Different Parts

‘Climate surprises’ assesses the possibility that there are thresholds or tipping points in the climate system that may occur as we warm the planet. Scientists have been concerned about these tipping points over the last three decades. One can examine the way different parts of the climate system respond to climate change with four scenarios. These include linear but delayed response; muted or limited response; delayed and non-linear response; and threshold response. It is worth considering here the melting of the Greenland and/or Western Antarctic ice sheet; the slowing down of the North Atlantic deep ocean circulation; the potential massive release of methane from melting gas hydrates; and the possibility of the Amazon rainforest dieback.

Assessing temperature fingerprints for the Atlantic overturning in the past two millennia

2020 ◽  
Author(s):  
Reyhan Shirin Ermis ◽  
Paola Moffa-Sánchez ◽  
Alexandra Jahn ◽  
Kira Rehfeld
Keyword(s):  
Time Scales ◽  
Ocean Circulation ◽  
North Atlantic ◽  
Time Scale ◽  
Deep Ocean ◽  
Meridional Overturning Circulation ◽  
The North ◽  
Surface Temperatures ◽  
Temperature Reconstructions ◽  
The North Atlantic

<p>The Atlantic Meridional Overturning Circulation (AMOC) is essential to maintain the temperate climates of Europe and North America. It redistributes heat from the tropics, and stores carbon in the deep ocean. Yet, its variability and evolution are largely unknown due to the lack of long-term direct circulation measurements. Previous studies suggest a connection between the variability of the AMOC strength and a temperature dipole in the North Atlantic. These results suggest a substantial decline in the strength of the overturning at the onset of the industrial era. </p><p>Here we compare temperature reconstructions from four sediment cores in the North Atlantic with model simulations of the Community Earth System Model (CESM1) as well as the Hadley Centre Coupled Model (HadCM3) over the Common Era. By examining the correlation between the surface temperatures in the North Atlantic and the strength of the overturning we test the robustness of previously used temperature fingerprints. Analysing variability in the surface and subsurface temperatures as well as the overturning strength in models we assess possible drivers of variability in ocean circulation. We compare the persistence times and the time scale dependent variability of the AMOC, the surface and ocean temperatures in the model with those in the temperature reconstructions. The sub-surface reconstructions match with the 200m ocean temperatures in persistence times but not with the AMOC in the models. The surface temperatures in the models show persistence times similar to those obtained for the AMOC. However, time scale dependent variabilities in the surface temperatures do not match those found the AMOC. Therefore, temperature fingerprints might not be a reliable basis to reconstruct the ocean overturning strength.</p><p>Due to the systematic comparison of two models on different time scales and an assessment of surface to sub-surface temperatures this study could provide new insights into the variability of Atlantic overturning on decadal time scales and beyond.</p>

scholarly journals Surface and deep water circulation in late Cretaceous North Atlantic greenhouse ocean

2009 ◽  
Author(s):  
◽  
Carolina Isaza Londoño
Keyword(s):  
Ocean Circulation ◽  
Late Cretaceous ◽  
North Atlantic ◽  
Deep Water ◽  
Water Mass ◽  
Deep Ocean ◽  
Water Circulation ◽  
Regional Warming ◽  
The North ◽  
The North Atlantic

This research provides the first of its kind empirical data regarding the evolution of Maastrichtian surface to deep ocean circulation in the North Atlantic. Differences in foraminiferal abundances and oxygen and carbon isotopic ratios of bulk carbonate and foraminifera between two Ocean Drilling Program Sites in the subtropical North Atlantic indicate a sharp water mass boundary was a relatively stable and persistent feature of the Maastrichtian North Atlantic despite significant regional warming across the interval. Neodymium isotopes of fish debris, on the other hand, indicate significant changes in intermediate and deep water circulation through the Late Cretaceous and especially during the Maastrichtian. During the Cenomanian-Campanian interval at least three different deep water masses were active in the North Atlantic including one formed by downwelling of warm saline waters in the Demerara Rise region. During the Campanian-Maastrichtian, low-latitude-sourced waters seem to have reached abyssal depths, but from the mid-Maastrichtian on, this water mass seems to have declined in importance. From the mid-Danian on, we found evidence for only one water mass (plausibly sourced in the northern North Atlantic, as it is today) at bathyal and abyssal depths in the North Atlantic. Our data demonstrate that surface and, especially, intermediate and deep water circulation patterns are an important (and measurable) variable that helps determine greenhouse temperature distributions on regional and global scales.

scholarly journals Regional and global signals in seawater δ18O records across the mid-Pleistocene transition

Geology ◽  
2019 ◽  
Vol 48 (2) ◽  
pp. 113-117 ◽  
Author(s):  
Heather L. Ford ◽  
Maureen E. Raymo
Keyword(s):  
Ocean Circulation ◽  
North Pacific Ocean ◽  
Deep Ocean ◽  
Ocean Drilling Program ◽  
Ocean Drilling ◽  
Ice Volume ◽  
The North ◽  
Global Ice Volume ◽  
Deep Ocean Water ◽  
Deep Ocean Circulation

Abstract High-resolution seawater δ18O records, derived from coupled Mg/Ca and benthic δ18O analyses, can be used to evaluate how global ice volume changed during the mid-Pleistocene transition (MPT, ca. 1250–600 ka). However, such seawater δ18O records are also influenced by regional hydrographic signals (i.e., salinity) and changes in deep-ocean circulation across the MPT, making it difficult to isolate the timing and magnitude of the global ice volume change. To explore regional and global patterns in seawater δ18O records, we reconstruct seawater δ18O from coupled Mg/Ca and δ18O analyses of Uvigerina spp. at Ocean Drilling Program Site 1208 in the North Pacific Ocean. Comparison of individual seawater δ18O records suggests that deep-ocean circulation reorganized and the formation properties (i.e., salinity) of deep-ocean water masses changed at ca. 900 ka, likely related to the transition to marine-based ice sheets in Antarctica. We also find that an increase in ice volume likely accompanied the shift in glacial-interglacial periodicity observed in benthic carbonate δ18O across the MPT, with increases in ice volume observed during Marine Isotope Stages 22 and 16.

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