Archives par mot-clé : Ocean

Température des océans: la fiabilité des calculs remise en cause

by Le Vif, 31 octobre 2017


Les scientifiques en déduisent que le réchauffement global actuel pourrait potentiellement être “sans précédent” sur les 100 derniers millions d’années. L’étude de ces géochimistes, publiée dans Nature Communications, constitue une sorte de pavé dans la mare des paléoclimatologues qui utilisent depuis les années 1950 ce “paléothermomètre” aidant à bâtir les modèles actuels sur le réchauffement climatique

The End Of The Ocean Acidification Scare For Corals

by McCulloch et al., 2017, October 2017,  in co2science


Paper Reviewed: McCulloch, M.T., D’Olivo, J.P., Falter, J., Holcomb, M. and Trotter, J.A. 2017. Coral calcification in a changing world and the interactive dynamics of pH and DIC upregulation. Nature Communications 8: 15686, DOI:10.1038/ncomms15686

(…) The implications of the above findings are enormous, for they reveal that “pHcf upregulation occurs largely independent of changes in seawater carbonate chemistry, and hence ocean acidification,” demonstrating “the ability of the coral to ‘control’ what is arguably one of its most fundamental physiological processes, the growth of its skeleton within which it lives.

See also here

The Little Boy, El Nino and Natural Climate Change

by Anastasios Tsonis, September 15, 2017 in GWPF Report26 (.pdf)


This report describes this phenomenon and brings it into a modern global con- text. But the story is more than simply one of some old South American geophysical phenomenology seen from a global perspective; it is tied to an extraordinary story about new scienti c thinking, arising at the end of the 20th century, concerning the nature of change itself.

The onset of widespread marine red beds and the evolution of ferruginous oceans

by Haijun Song et al., August 2017, in Nature


Banded iron formations were a prevalent feature of marine sedimentation ~3.8–1.8 billion years ago and they provide key evidence for ferruginous oceans. The disappearance of banded iron formations at ~1.8 billion years ago was traditionally taken as evidence for the demise of ferruginous oceans, but recent geochemical studies show that ferruginous conditions persisted throughout the later Precambrian, and were even a feature of Phanerozoic ocean anoxic events.

Statistical link between external climate forcings and modes of ocean variability

by Abdul Malik et al., July 31, 2017, Climate Dynamics, Springer


In this study we investigate statistical link between external climate forcings and modes of ocean variability on inter-annual (3-year) to centennial (100-year) timescales using de-trended semi-partial-cross-correlation analysis technique. To investigate this link we employ observations (AD 1854–1999), climate proxies (AD 1600–1999), and coupled Atmosphere-Ocean-Chemistry Climate Model simulations with SOCOL-MPIOM (AD 1600–1999). We find robust statistical evidence that Atlantic multi-decadal oscillation (AMO) has intrinsic positive correlation with solar activity in all datasets employed. The strength of the relationship between AMO and solar activity is modulated by volcanic eruptions and complex interaction among modes of ocean variability.

Cooling Deep Oceans – and the Earth’s General Background Temperature

by Wim Röst, August 13, in WUWT (Andy May)


Five million years ago, average temperatures were higher than they are now. During the Pliocene, the era just before the period of the Quaternary Ice Ages, ‘glacials’ did not yet exist because temperatures were too high. As cooling of the deep seas continued, temperatures became that low that large surfaces of the Northern Hemisphere became covered with snow. The earth’s albedo grew fast and large ice sheets started to develop

“New study challenges prevailing theory about how deep-sea vents are colonized”… And hydrothermal oil!

by David Middleton, August 4, 2017 in WUWT


An article just published in the Proceedings of the Royal Society B describes two remarkably different hydrothermal vent fields discovered in the southern Gulf of California. Despite being relatively close together, these vents host very different animal communities. This finding contradicts a common scientific assumption that neighboring vents will share similar animal communities. Instead, the new paper suggests that local geology and the chemistry of the vent fluids are important factors affecting vent communities

See aslo here

Skillful prediction of northern climate provided by the ocean

by M. Arthur et al., June 20, 2017, in Nature Communication


We show that variations in ocean temperature in the high latitude North Atlantic and Nordic Seas are reflected in the climate of northwestern Europe and in winter Arctic sea ice extent. Statistical regression models show that a significant part of northern climate variability thus can be skillfully predicted up to a decade in advance based on the state of the ocean. Particularly, we predict that Norwegian air temperature will decrease over the coming years, although staying above the long-term (1981–2010) average. Winter Arctic sea ice extent will remain low but with a general increase towards 2020.

Ocean Warming Dominates The Increase In Energy Stored In the Climate System

by CO2 is Life, May 13, 2017


The basic physics behind CO2 warming the oceans, and therefore the atmosphere simply don’t exist. The only defined mechanism by which CO2 can affect climate change is by “thermalizing” long-wave infrared radiation between 13 and 18-microns. In reality, there is another one, radiation,  but that carries heat away from the earth and results in atmospheric cooling.

River plastic emissions to the world’s oceans

by Laurent Lebreton et al., June 7, 2017 in Nature Communication


Plastics in the marine environment have become a major concern because of their persistence at sea, and adverse consequences to marine life and potentially human health. Implementing mitigation strategies requires an understanding and quantification of marine plastic sources, taking spatial and temporal variability into account. Here we present a global model of plastic inputs from rivers into oceans based on waste management, population density and hydrological information.

Threshold in North Atlantic-Arctic Ocean circulation controlled by the subsidence of the Greenland-Scotland Ridge

by Michael Stars et al., June 5, 2017 in Nature Communication


High latitude ocean gateway changes are thought to play a key role in Cenozoic climate evolution. However, the underlying ocean dynamics are poorly understood. Here we use a fully coupled atmosphere-ocean model to investigate the effect of ocean gateway formation that is associated with the subsidence of the Greenland–Scotland Ridge. We find a threshold in sill depth (50 m) that is linked to the influence of wind mixing.

Early 20th-century Arctic warming intensified by Pacific and Atlantic multidecadal variability

by Hiroki Tokinaga et al., PNAS, May 1, 2017


Arctic amplification is a robust feature of climate response to global warming, with large impacts on ecosystems and societies. A long-standing mystery is that a pronounced Arctic warming occurred during the early 20th century when the rate of interdecadal change in radiative forcing was much weaker than at present. Here, using observations and model experiments, we show that the combined effect of internally generated Pacific and Atlantic interdecadal variabilities intensified the Arctic land warming in the early 20th century.

A paleo-perspective on ocean heat content: Lessons from the Holocene and Common Era

by Yair Rosenthal et al., January 1, 2017


 

Here we review proxy records of intermediate water temperatures from sediment cores in the equatorial Pacific and northeastern Atlantic Oceans, spanning 10,000 years beyond the instrumental record.

These records suggests that intermediate waters were 1.5–2 °C warmer during the Holocene Thermal Maximum than in the last century.

Intermediate water masses cooled by 0.9 °C from the Medieval Climate Anomaly to the Little Ice Age.

 

When will Earth lose its oceans?

by J.  Lecomte et al., CNRS, December 16, 2013

The natural increase in solar luminosity — a very slow process unrelated to current climate warming — will cause the Earth’s temperatures to rise over the next few hundred million years. This will result in the complete evaporation of the oceans. The first three-dimensional climate model able to simulate the phenomenon predicts that liquid water will disappear on Earth in approximately one billion years, extending previous estimates by several hundred million years.

Jérémy Leconte, Francois Forget, Benjamin Charnay, Robin Wordsworth, Alizée Pottier. Increased insolation threshold for runaway greenhouse processes on Earth-like planetsNature, 2013; 504 (7479): 268 DOI: 10.1038/nature12827

 

Atlantique Nord : le risque d’un refroidissement rapide au XXIe siècle revu à la hausse

par D. Swingedouw et al., CNRS, 15 février 2017


Dans le cadre du projet européen EMBRACE, une équipe d’océanographes a réexaminé ces 40 projections climatiques en se focalisant sur un point névralgique au nord-ouest de l’Atlantique Nord : la mer du Labrador. Cette mer est le siège d’un phénomène de convection, qui nourrit à plus grande échelle la circulation océanique de retournement. Ses eaux de surface se refroidissent fortement en hiver, deviennent plus denses que les eaux de profondeur et plongent vers le fond. La chaleur des eaux profondes est transférée vers la surface et empêche la formation de banquise