scholarly journals Dependence of abrupt Atlantic meridional ocean circulation changes on climate background states

2013 ◽  
Vol 40 (14) ◽  
pp. 3698-3704 ◽  
Author(s):  
Xun Gong ◽  
Gregor Knorr ◽  
Gerrit Lohmann ◽  
Xu Zhang
Keyword(s):  
Ocean Circulation ◽  
Climate Background ◽  
Circulation Changes

scholarly journals Relative timing of precipitation and ocean circulation changes in the western equatorial Atlantic over the last 45 kyr

2018 ◽  
Vol 14 (9) ◽  
pp. 1315-1330 ◽  
Author(s):  
Claire Waelbroeck ◽  
Sylvain Pichat ◽  
Evelyn Böhm ◽  
Bryan C. Lougheed ◽  
Davide Faranda ◽  
...  
Keyword(s):  
Mass Transport ◽  
Ocean Circulation ◽  
North Atlantic ◽  
Wavelet Transforms ◽  
Water Mass ◽  
Sediment Cores ◽  
Equatorial Atlantic ◽  
The North ◽  
Atmospheric Changes ◽  
Circulation Changes

Abstract. Thanks to its optimal location on the northern Brazilian margin, core MD09-3257 records both ocean circulation and atmospheric changes. The latter occur locally in the form of increased rainfall on the adjacent continent during the cold intervals recorded in Greenland ice and northern North Atlantic sediment cores (i.e., Greenland stadials). These rainfall events are recorded in MD09-3257 as peaks in ln(Ti ∕ Ca). New sedimentary Pa ∕ Th data indicate that mid-depth western equatorial water mass transport decreased during all of the Greenland stadials of the last 40 kyr. Using cross-wavelet transforms and spectrogram analysis, we assess the relative phase between the MD09-3257 sedimentary Pa ∕ Th and ln(Ti ∕ Ca) signals. We show that decreased water mass transport between a depth of ∼1300 and 2300 m in the western equatorial Atlantic preceded increased rainfall over the adjacent continent by 120 to 400 yr at Dansgaard–Oeschger (D–O) frequencies, and by 280 to 980 yr at Heinrich-like frequencies. We suggest that the large lead of ocean circulation changes with respect to changes in tropical South American precipitation at Heinrich-like frequencies is related to the effect of a positive feedback involving iceberg discharges in the North Atlantic. In contrast, the absence of widespread ice rafted detrital layers in North Atlantic cores during D–O stadials supports the hypothesis that a feedback such as this was not triggered in the case of D–O stadials, with circulation slowdowns and subsequent changes remaining more limited during D–O stadials than Heinrich stadials.

The Southern Ocean and its interaction with the Antarctic Ice Sheet

Science ◽  
2020 ◽  
Vol 367 (6484) ◽  
pp. 1326-1330
Author(s):  
David M. Holland ◽  
Keith W. Nicholls ◽  
Aurora Basinski
Keyword(s):  
Southern Ocean ◽  
Ocean Circulation ◽  
Thermal Structure ◽  
Ice Sheet ◽  
Major Influence ◽  
Antarctic Ice Sheet ◽  
Ice Shelves ◽  
Air Temperatures ◽  
The Antarctic ◽  
Circulation Changes

The Southern Ocean exerts a major influence on the mass balance of the Antarctic Ice Sheet, either indirectly, by its influence on air temperatures and winds, or directly, mostly through its effects on ice shelves. How much melting the ocean causes depends on the temperature of the water, which in turn is controlled by the combination of the thermal structure of the surrounding ocean and local ocean circulation, which in turn is determined largely by winds and bathymetry. As climate warms and atmospheric circulation changes, there will be follow-on changes in the ocean circulation and temperature. These consequences will affect the pace of mass loss of the Antarctic Ice Sheet.

Global-ocean circulation changes during the Smithian–Spathian transition inferred from carbon‑sulfur cycle records

2019 ◽  
Vol 195 ◽  
pp. 114-132 ◽  
Author(s):  
Zhengyi Lyu ◽  
Lei Zhang ◽  
Thomas J. Algeo ◽  
Laishi Zhao ◽  
Zhong-Qiang Chen ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Sulfur Cycle ◽  
Global Ocean ◽  
Global Ocean Circulation ◽  
Circulation Changes

scholarly journals Atlantic Ocean circulation changes preceded millennial tropical South America rainfall events during the last glacial

2015 ◽  
Vol 42 (2) ◽  
pp. 411-418 ◽  
Author(s):  
Pierre Burckel ◽  
Claire Waelbroeck ◽  
Jeanne Marie Gherardi ◽  
Sylvain Pichat ◽  
Helge Arz ◽  
...  
Keyword(s):  
South America ◽  
Atlantic Ocean ◽  
Ocean Circulation ◽  
Rainfall Events ◽  
Last Glacial ◽  
Circulation Changes ◽  
The Last Glacial ◽  
Tropical South America

scholarly journals Evidence for Two Distinct Modes of Large-Scale Ocean Circulation Changes over the Last Century

2010 ◽  
Vol 23 (1) ◽  
pp. 5-16 ◽  
Author(s):  
Mihai Dima ◽  
Gerrit Lohmann
Keyword(s):  
Ocean Circulation ◽  
North Atlantic ◽  
Large Scale ◽  
Climate Changes ◽  
Thermohaline Circulation ◽  
Conveyor Belt ◽  
The North ◽  
Symmetric Pattern ◽  
The North Atlantic ◽  
Circulation Changes

Abstract Through its nonlinear dynamics and involvement in past abrupt climate shifts the thermohaline circulation (THC) represents a key element for the understanding of rapid climate changes. The expected THC weakening under global warming is characterized by large uncertainties, and it is therefore of significant importance to identify ocean circulation changes over the last century. By applying various statistical techniques on two global sea surface temperature datasets two THC-related modes are separated. The first one involves relatively slow adjustment of the whole conveyor belt circulation and has an interhemispherically symmetric pattern. The second mode is associated with the relatively fast adjustment of the North Atlantic overturning cell and has the seesaw structure. Based on the separation of these two patterns the authors show that the global conveyor has been weakening since the late 1930s and that the North Atlantic overturning cell suffered an abrupt shift around 1970. The distinction between the two modes provides also a new frame for interpreting past abrupt climate changes.

scholarly journals Mechanisms of Internal Atlantic Multidecadal Variability in HadGEM3-GC3.1 at Two Different Resolutions

2021 ◽  
pp. 1-60
Author(s):  
J. I. Robson ◽  
L. J. Wilcox ◽  
N. Dunstone
Keyword(s):  
Ocean Circulation ◽  
Low Frequency ◽  
Heat Fluxes ◽  
The Arctic ◽  
Western Boundary ◽  
Atlantic Multidecadal Variability ◽  
Surface Heat Fluxes ◽  
Ocean Salinity ◽  
Circulation Changes ◽  
Sst Anomalies

Abstract This study broadly characterises and compares the key processes governing internal AMV in two resolutions of HadGEM3-GC3.1: N216ORCA025, corresponding to ~ 60km in the atmosphere and 0.25° in the ocean, and N96ORCA1 (~ 135km / 1°). Both models simulate AMV with a timescale of 60-80 years, which is related to low frequency ocean and atmosphere circulation changes. In both models, ocean heat transport convergence dominates polar and subpolar AMV, whereas surface heat fluxes associated with cloud changes drive subtropicalAMV. However, details of the ocean circulation changes differ between the models. In N216 subpolar subsurface density anomalies propagate into the subtropics along the western boundary, consistent with the more coherent circulation changes and widespread development of SST anomalies. In contrast, N96 subsurface density anomalies persist in the subpolar latitudes for longer, so circulation anomalies and the development of SST anomalies are more centred there. The drivers of subsurface density anomalies also differ between models. In N216, the NAO is the dominant driver, while upper-ocean salinity-controlled density anomalies that originate from the Arctic appear to be the dominant driver in N96. These results further highlight that internal AMV mechanisms are model dependent and motivate further work to better understand and constrain the differences.

CO2-driven ocean circulation changes as an amplifier of Paleocene-Eocene thermal maximum hydrate destabilization

Geology ◽  
2010 ◽  
Vol 38 (10) ◽  
pp. 875-878 ◽  
Author(s):  
Daniel J. Lunt ◽  
Paul J. Valdes ◽  
Tom Dunkley Jones ◽  
Andy Ridgwell ◽  
Alan M. Haywood ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Thermal Maximum ◽  
Circulation Changes

scholarly journals Connecting Changing Ocean Circulation with Changing Climate

2013 ◽  
Vol 26 (7) ◽  
pp. 2268-2278 ◽  
Author(s):  
Michael Winton ◽  
Stephen M. Griffies ◽  
Bonita L. Samuels ◽  
Jorge L. Sarmiento ◽  
Thomas L. Frölicher
Keyword(s):  
Carbon Storage ◽  
Ocean Circulation ◽  
Radiative Forcing ◽  
Heat Storage ◽  
Cooling Power ◽  
Carbon Uptake ◽  
Ocean Heat Uptake ◽  
Climate Gradients ◽  
The Impact ◽  
Circulation Changes

Abstract The influence of changing ocean currents on climate change is evaluated by comparing an earth system model’s response to increased CO2 with and without an ocean circulation response. Inhibiting the ocean circulation response, by specifying a seasonally varying preindustrial climatology of currents, has a much larger influence on the heat storage pattern than on the carbon storage pattern. The heat storage pattern without circulation changes resembles carbon storage (either with or without circulation changes) more than it resembles the heat storage when currents are allowed to respond. This is shown to be due to the larger magnitude of the redistribution transport—the change in transport due to circulation anomalies acting on control climate gradients—for heat than for carbon. The net ocean heat and carbon uptake are slightly reduced when currents are allowed to respond. Hence, ocean circulation changes potentially act to warm the surface climate. However, the impact of the reduced carbon uptake on radiative forcing is estimated to be small while the redistribution heat transport shifts ocean heat uptake from low to high latitudes, increasing its cooling power. Consequently, global surface warming is significantly reduced by circulation changes. Circulation changes also shift the pattern of warming from broad Northern Hemisphere amplification to a more structured pattern with reduced warming at subpolar latitudes in both hemispheres and enhanced warming near the equator.

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