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There is increasing concern that the Atlantic Meridional Overturning Circulation (AMOC) may collapse this century with a disrupting societal impact on large parts of the world. Preliminary estimates of the probability of such an AMOC collapse have so far been based on conceptual models and statistical analyses of proxy data. Here, we provide observationally based estimates of such probabilities from reanalysis data. We first identify optimal observation regions of an AMOC collapse from a recent global climate model simulation. Salinity data near the southern boundary of the Atlantic turn out to be optimal to provide estimates of the time of the AMOC collapse in this model. Based on the reanalysis products, we next determine probability density functions of the AMOC collapse time. The collapse time is estimated between 2037-2064 (10-90% CI) with a mean of 2050 and the probability of an AMOC collapse before the year 2050 is estimated to be 59±17%.

Ce rapport analyse les obstacles et leviers à la lumière de projets inspirants en matière d'adaptation des villes à l'élévation du niveau de la mer dans le Pacifique.

Anthropogenic emissions drive global-scale warming yet the temperature increase relative to pre-industrial levels is uncertain. Using 300 years of ocean mixed-layer temperature records preserved in sclerosponge carbonate skeletons, we demonstrate that industrial-era warming began in the mid-1860s, more than 80 years earlier than instrumental sea surface temperature records. The Sr/Ca palaeothermometer was calibrated against ‘modern’ (post-1963) highly correlated (R2 = 0.91) instrumental records of global sea surface temperatures, with the pre-industrial defined by nearly constant (<±0.1 °C) temperatures from 1700 to the early 1860s. Increasing ocean and land-air temperatures overlap until the late twentieth century, when the land began warming at nearly twice the rate of the surface oceans. Hotter land temperatures, together with the earlier onset of industrial-era warming, indicate that global warming was already 1.7 ± 0.1 °C above pre-industrial levels by 2020. Our result is 0.5 °C higher than IPCC estim

L'histoire d'une course technologique fatale contre le thon et la vie marine

La Niña is present.* Equatorial sea surface temperatures (SSTs) are below average across most of the Pacific Ocean. The tropical Pacific atmosphere is consistent with La Niña. La Niña is expected to continue into the winter, with equal chances of La Niña and ENSO-neutral during January-March 2023. In February-April 2023, there is a 71% chance of ENSO-neutral.*

Ce policy brief propose une série de recommandations et appelle au renforcement des connaissances en amont de l’implantation d’éoliennes en mer. Il prône une meilleure connaissance du fonctionnement des écosystèmes marins, des impacts cumulés des activités humaines existantes et des impacts sur le milieu marin du changement climatique, afin de guider la planification notamment dans le choix des zones d’implantation des éoliennes.

Par cette Déclaration, les parlementaires du monde entier s’unissent pour appeler à un moratoire sur l’exploitation minière des grands fonds marins, pour adopter un principe de précaution afin de préserver ce patrimoine commun de l’humanité, et pour protéger les droits humains de toutes les personnes qui dépendent des océans.

The Status of Coral Reefs of the World: 2020 (L'état des récifs coralliens dans le monde : 2020) est un rapport du Réseau mondial de surveillance continue des récifs coralliens (GCRMN), un réseau de l'Initiative internationale pour les récifs coralliens (ICRI). Ses conclusions montrent qu'entre 2009 et 2018, une perte progressive d'environ 14 % des coraux dans les récifs coralliens du monde a été enregistrée, principalement causée par des épisodes de blanchiment récurrents à grande échelle. Au total, environ 11 700 kilomètres carrés de coraux durs ont été perdus, ce qui représente plus de la totalité des coraux vivant actuellement dans les récifs coralliens de l'Australie.

The Atlantic Meridional Overturning Circulation (AMOC), a major ocean current system transporting warm surface waters toward the northern Atlantic, has been suggested to exhibit two distinct modes of operation. A collapse from the currently attained strong to the weak mode would have severe impacts on the global climate system and further multi-stable Earth system components. Observations and recently suggested fingerprints of AMOC variability indicate a gradual weakening during the last decades, but estimates of the critical transition point remain uncertain.

Plants should be flourishing in these ocean waters with plenty of nutrients and inorganic carbon in the form carbonic acid. It could be possible the phytoplankton are missing key nutrients such as ferric, but why should this be happening now?

A new report, published on 14 March, 2021 in the Royal Swedish Academy of Sciences’ journal Ambio, points out that humanity is hurtling towards destruction unless we have the collective wisdom to change course quickly.

SI vous vous êtes déjà demandé quel était le lien entre la montée du niveau des océans et le changement climatique, nous espérons que cette planche vous aidera à y voir plus clair. Nous avons bénéficié de l'aide d'Anny Cazenave, chercheuse CNES au LEGOS (Laboratoire d'études en géophysique et océanographie spatiales), membre de l’Académie des sciences et l’un des principaux auteurs du chapitre « Élévation du niveau de la mer » du 5e rapport du Groupe d'experts intergouvernemental sur l'évolution du climat (GIEC).

Le WWF publie un nouveau rapport qui dresse un constat alarmant sur la pollution plastique en Méditerranée et analyse la responsabilité des 22 pays méditerranéens face à ce fléau.

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. Our model is calibrated against measurements available in the literature. We estimate that between 1.15 and 2.41 million tonnes of plastic waste currently enters the ocean every year from rivers, with over 74% of emissions occurring between May and October. The top 20 polluting rivers, mostly located in Asia, account for 67% of the global total. The findings of this study provide baseline data for ocean plastic mass balance exercises, and assist in prioritizing future plastic debris monitoring and mitigation strategies. Rivers provide a m