scholarly journals Tiny Marine Shells Reveal Past Patterns in Ocean Dynamics

Eos ◽  
2018 ◽  
Vol 99 ◽  
Author(s):  
Aaron Sidder
Keyword(s):  
Carbon Dioxide ◽  
Calcium Carbonate ◽  
Ocean Circulation ◽  
Atmospheric Carbon Dioxide ◽  
Deep Ocean ◽  
Ocean Dynamics ◽  
Ocean Floor ◽  
Carbon Dioxide Concentrations ◽  
Climate Patterns ◽  
Deep Ocean Circulation

A 400,000-year calcium carbonate record from the ocean floor sheds light on deep-ocean circulation and on mechanisms driving climate patterns and atmospheric carbon dioxide concentrations.

scholarly journals Glacial ocean circulation and stratification explained by reduced atmospheric temperature

2016 ◽  
Vol 114 (1) ◽  
pp. 45-50 ◽  
Author(s):  
Malte F. Jansen
Keyword(s):  
Ocean Circulation ◽  
Atmospheric Carbon Dioxide ◽  
Formation Rate ◽  
Deep Ocean ◽  
Direct Consequence ◽  
Atmospheric Temperature ◽  
Overturning Circulation ◽  
Last Glacial ◽  
Deep Ocean Circulation ◽  
The Last Glacial

Earth’s climate has undergone dramatic shifts between glacial and interglacial time periods, with high-latitude temperature changes on the order of 5–10 °C. These climatic shifts have been associated with major rearrangements in the deep ocean circulation and stratification, which have likely played an important role in the observed atmospheric carbon dioxide swings by affecting the partitioning of carbon between the atmosphere and the ocean. The mechanisms by which the deep ocean circulation changed, however, are still unclear and represent a major challenge to our understanding of glacial climates. This study shows that various inferred changes in the deep ocean circulation and stratification between glacial and interglacial climates can be interpreted as a direct consequence of atmospheric temperature differences. Colder atmospheric temperatures lead to increased sea ice cover and formation rate around Antarctica. The associated enhanced brine rejection leads to a strongly increased deep ocean stratification, consistent with high abyssal salinities inferred for the last glacial maximum. The increased stratification goes together with a weakening and shoaling of the interhemispheric overturning circulation, again consistent with proxy evidence for the last glacial. The shallower interhemispheric overturning circulation makes room for slowly moving water of Antarctic origin, which explains the observed middepth radiocarbon age maximum and may play an important role in ocean carbon storage.

scholarly journals Snowfall-albedo feedbacks could have led to deglaciation of snowball Earth starting from mid-latitudes

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Philipp de Vrese ◽  
Tobias Stacke ◽  
Jeremy Caves Rugenstein ◽  
Jason Goodman ◽  
Victor Brovkin
Keyword(s):  
Carbon Dioxide ◽  
Atmospheric Carbon Dioxide ◽  
Climate Models ◽  
Hydrological Cycle ◽  
High Surface ◽  
Dust Deposition ◽  
Carbon Dioxide Concentrations ◽  
Maximum Temperatures ◽  
Carbon Dioxide Levels ◽  
Earth’S Climate

AbstractSimple and complex climate models suggest a hard snowball – a completely ice-covered planet – is one of the steady-states of Earth’s climate. However, a seemingly insurmountable challenge to the hard-snowball hypothesis lies in the difficulty in explaining how the planet could have exited the glaciated state within a realistic range of atmospheric carbon dioxide concentrations. Here, we use simulations with the Earth system model MPI-ESM to demonstrate that terminal deglaciation could have been triggered by high dust deposition fluxes. In these simulations, deglaciation is not initiated in the tropics, where a strong hydrological cycle constantly regenerates fresh snow at the surface, which limits the dust accumulation and snow aging, resulting in a high surface albedo. Instead, comparatively low precipitation rates in the mid-latitudes in combination with high maximum temperatures facilitate lower albedos and snow dynamics that – for extreme dust fluxes – trigger deglaciation even at present-day carbon dioxide levels.

Deep-ocean circulation in the North Atlantic during the Plio-Pleistocene intensification of Northern Hemisphere Glaciation (~2.65–2.4 Ma)

2021 ◽  
pp. 101998
Author(s):  
Kim A. Jakob ◽  
Jörg Pross ◽  
Jasmin M. Link ◽  
Patrick Blaser ◽  
Anna Hauge Braaten ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Ocean Circulation ◽  
North Atlantic ◽  
Deep Ocean ◽  
The North ◽  
The North Atlantic ◽  
Deep Ocean Circulation

scholarly journals The Influence of Ocean Thermocline Temperatures on the Earth’s Surface Climate

2005 ◽  
Vol 18 (13) ◽  
pp. 2222-2246 ◽  
Author(s):  
Robert J. Oglesby ◽  
Monica Y. Stephens ◽  
Barry Saltzman
Keyword(s):  
Carbon Dioxide ◽  
Mixed Layer ◽  
General Circulation ◽  
Atmospheric Carbon Dioxide ◽  
Deep Ocean ◽  
High Latitudes ◽  
Surface Climate ◽  
Low Latitudes ◽  
Atmospheric Carbon ◽  
The Impact

Abstract A coupled mixed layer–atmospheric general circulation model has been used to evaluate the impact of ocean thermocline temperatures (and by proxy those of the deep ocean) on the surface climate of the earth. Particular attention has been devoted to temperature regimes both warmer and cooler than at present. The mixed layer ocean model (MLOM) simulates vertical dynamics and thermodynamics in the upper ocean, including wind mixing and buoyancy effects, and has been coupled to the NCAR Community Climate Model (CCM3). Simulations were made with globally uniform thermocline warmings of +2°, +5°, and +10°C, as well as a globally uniform cooling of −5°C. A simulation was made with latitudinally varying changes in thermocline temperature such that the warming at mid- and high latitudes is much larger than at low latitudes. In all simulations, the response of surface temperature over both land and ocean was larger than that expected just as a result of the imposed thermocline temperature change, largely because of water vapor feedbacks. In this respect, the simulations were similar to those in which only changes in atmospheric carbon dioxide were imposed. In fact, when carbon dioxide was explicitly changed along with thermocline temperatures, the results were not much different than if only the thermocline temperatures were altered. Land versus ocean differences are explained largely by latent heat flux differences: the ocean is an infinite evaporative source, while land can be quite dry. The latitudinally varying case has a much larger response at mid- to high latitudes than at low latitudes; the high latitudes actually appear to effectively warm the low latitudes. Simulations exploring scenarios of glacial inception suggest that the deep ocean alone is not likely to be a key trigger but must operate in conjunction with other forcings, such as reduced carbon dioxide. Moist upland regions at mid- and high latitudes, and land regions adjacent to perennial sea ice, are the preferred locations for glacial inception in these runs. Finally, the model combination equilibrates very rapidly, meaning that a large number of simulations can be made for a fairly modest computational cost. A drawback to this is greatly reduced sensitivity to parameters such as atmospheric carbon dioxide, which requires a full response of the ocean. Thus, this approach can be considered intermediate between fixing, or prescribing, sea surface temperatures and a fully coupled modeling approach.

The rate of dissolution of calcium carbonate from the surface of deep-ocean turbidite sediments

1990 ◽  
Vol 331 (1616) ◽  
pp. 41-49 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Atmospheric Carbon Dioxide ◽  
Bottom Water ◽  
Natural Radionuclide ◽  
Carbon Dioxide Concentration ◽  
Deep Ocean ◽  
Sediment Surface ◽  
Carbonate Sediments ◽  
Sedimentary Record ◽  
Atmospheric Carbon

It is known that past periods of high atmospheric carbon dioxide concentration are associated with poor carbonate preservation in the deep-ocean sedimentary record. Bottom water can become more aggressive towards carbonate sediments during such periods. To interpret the sedimentary record more exactly, and to predict future atmospheric carbon dioxide levels, it is necessary to know the rate of solution of carbonate for a given degree of bottom-water undersaturation. In parts of the Atlantic Ocean, turbidite sedimentation mechanisms have emplaced carbonate-rich material in contact with undersaturated bottom water. The time of the emplacement event can be determined from natural radionuclide distributions, and the degree of carbonate dissolution in this time can be measured. This provides a direct measurement of dissolution rate from a natural sediment surface at a known degree of undersaturation. The range of applicability of the method is explored with a mathematical model, and field data from a 5430 m depth Atlantic site are presented.

scholarly journals Connecting Antarctic sea ice to deep-ocean circulation in modern and glacial climate simulations

2017 ◽  
Vol 44 (12) ◽  
pp. 6286-6295 ◽  
Author(s):  
Alice Marzocchi ◽  
Malte F. Jansen
Keyword(s):  
Sea Ice ◽  
Ocean Circulation ◽  
Deep Ocean ◽  
Antarctic Sea Ice ◽  
Climate Simulations ◽  
Deep Ocean Circulation ◽  
Glacial Climate

Modelling trends and volatility in atmospheric carbon dioxide concentrations

2006 ◽  
Vol 21 (9) ◽  
pp. 1273-1279 ◽  
Author(s):  
Michael McAleer ◽  
Felix Chan
Keyword(s):  
Carbon Dioxide ◽  
Atmospheric Carbon Dioxide ◽  
Carbon Dioxide Concentrations ◽  
Atmospheric Carbon
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