Filtering of Milankovitch Cycles by the Thermohaline Circulation

This paper investigates the long-term impact of sea ice on global climate using a global sea-ice–ocean general circulation model (OGCM). The sea-ice component involves state-of-the-art dynamics; the ocean component consists of a 3.5° × 3.5° × 11 layer primitive-equation model. Depending on the physical description of sea ice, significant changes are detected in the convective activity, in the hydrographic properties and in the thermohaline circulation of the ocean model. Most of these changes originate in the Southern Ocean, emphasizing the crucial role of sea ice in this marginally stably stratified region of the world's oceans. Specifically, if the effect of brine release is neglected, the deep layers of the Southern Ocean warm up considerably; this is associated with a weakening of the Southern Hemisphere overturning cell. The removal of the commonly used “salinity enhancement” leads to a similar effect. The deep-ocean salinity is almost unaffected in both experiments. Introducing explicit new-ice thickness growth in partially ice-covered gridcells leads to a substantial increase in convective activity, especially in the Southern Ocean, with a concomitant significant cooling and salinification of the deep ocean. Possible mechanisms for the resulting interactions between sea-ice processes and deep-ocean characteristics are suggested.

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Symmetric and asymmetric modes of the thermohaline circulation

Tellus A Dynamic Meteorology and Oceanography ◽

10.3402/tellusa.v58i5.14813 ◽

2006 ◽

Author(s):

Rezwan Mohammad ◽

Johan Nilsson

Keyword(s):

Thermohaline Circulation

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Stability of the thermohaline circulation in a simple coupled model

Tellus A Dynamic Meteorology and Oceanography ◽

10.3402/tellusa.v48i3.12072 ◽

1996 ◽

Vol 48 (3) ◽

pp. 465-476 ◽

Cited By ~ 4

Author(s):

Gerrit Lohmann ◽

Rüdiger Gerdes ◽

Deliang Chen

Keyword(s):

Thermohaline Circulation ◽

Coupled Model

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On Time Scales of Intrinsic Oscillations in the Climate System

Entropy ◽

10.3390/e23040459 ◽

2021 ◽

Vol 23 (4) ◽

pp. 459

Author(s):

Anastasios A. Tsonis ◽

Geli Wang ◽

Wenxu Lu ◽

Sergey Kravtsov ◽

Christopher Essex ◽

...

Keyword(s):

Low Frequency ◽

Milankovitch Cycles ◽

Data Sets ◽

External Forcing ◽

Natural Oscillations ◽

Climatic Oscillations ◽

Slow Feature Analysis ◽

Limited Length ◽

Past Data ◽

Cumulative Evidence

Proxy temperature data records featuring local time series, regional averages from areas all around the globe, as well as global averages, are analyzed using the Slow Feature Analysis (SFA) method. As explained in the paper, SFA is much more effective than the traditional Fourier analysis in identifying slow-varying (low-frequency) signals in data sets of a limited length. We find the existence of a striking gap from ~1000 to about ~20,000 years, which separates intrinsic climatic oscillations with periods ranging from ~ 60 years to ~1000 years, from the longer time-scale periodicities (20,000 yr +) involving external forcing associated with Milankovitch cycles. The absence of natural oscillations with periods within the gap is consistent with cumulative evidence based on past data analyses, as well as with earlier theoretical and modeling studies.

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Synergistic impacts of global warming and thermohaline circulation collapse on amphibians

Communications Biology ◽

10.1038/s42003-021-01665-6 ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Julián A. Velasco ◽

Francisco Estrada ◽

Oscar Calderón-Bustamante ◽

Didier Swingedouw ◽

Carolina Ureta ◽

...

Keyword(s):

Climate Change ◽

Global Warming ◽

Thermohaline Circulation ◽

Climate Model ◽

Global Climate ◽

Extinction Risk ◽

Meridional Overturning Circulation ◽

Mitigation Strategies ◽

Amphibian Species ◽

Climate Conditions

AbstractImpacts on ecosystems and biodiversity are a prominent area of research in climate change. However, little is known about the effects of abrupt climate change and climate catastrophes on them. The probability of occurrence of such events is largely unknown but the associated risks could be large enough to influence global climate policy. Amphibians are indicators of ecosystems’ health and particularly sensitive to novel climate conditions. Using state-of-the-art climate model simulations, we present a global assessment of the effects of unabated global warming and a collapse of the Atlantic meridional overturning circulation (AMOC) on the distribution of 2509 amphibian species across six biogeographical realms and extinction risk categories. Global warming impacts are severe and strongly enhanced by additional and substantial AMOC weakening, showing tipping point behavior for many amphibian species. Further declines in climatically suitable areas are projected across multiple clades, and biogeographical regions. Species loss in regional assemblages is extensive across regions, with Neotropical, Nearctic and Palearctic regions being most affected. Results underline the need to expand existing knowledge about the consequences of climate catastrophes on human and natural systems to properly assess the risks of unabated warming and the benefits of active mitigation strategies.

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