Chroniques du têtard mouillé: Climactualités

vendredi 29 septembre 2017

Climactualités - Septembre 2017

J'inaugure une rubrique sur l'actualité climatique du mois passé (on verra si je tiens la distance) dans laquelle j'entrepose pêle-mêle les articles que j'ai trouvés intéressants (mais j'ai pu, et dû, en louper un certain nombre) ; comme je n'ai pas toute la journée à dédier à la tenue de ce blog je me dispenserai de traduire les articles en français, à chacun donc de se débrouiller avec la langue de Shakespeare en fonction de ses capacités (il y a au demeurant des outils de traduction en ligne assez performants...)

Comme je ne ferai aucun commentaire (sauf pour les dessins humoristiques), me contentant de reprendre quelques extraits ou graphiques des articles en question, les lecteurs qui m'accuseraient de cherry-picking verraient leur prose automatiquement envoyée à la poubelle sans forcément une explication de ma part ; je donnerai à chaque fois les liens donc toute personne n'ayant pas de poil dans la main sera capable d'aller consulter les sources dans leur totalité.

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1/09/2017 : sciencedirect

Rapid drawdown of Antarctica's Wordie Ice Shelf glaciers in response to ENSO/Southern Annular Mode-driven warming in the Southern Ocean ( CC Walker, AS Gardner)

Abstract

Here we investigate the largest acceleration in ice flow across all of Antarctica between ∼2008 InSAR and 2014 Landsat velocity mappings. This occurred in glaciers that used to feed into the Wordie Ice Shelf on the west Antarctic Peninsula, which rapidly disintegrated in ∼1989. Between 2008 and 2014, these glaciers experienced at least a threefold increase in surface elevation drawdown relative to the 2002–2008 time period. After ∼20 yrs of relative stability, it is unlikely that the ice shelf collapse played a role in the large response. Instead, we find that the rapid acceleration and surface drawdown is linked to enhanced melting at the ice-ocean boundary, attributable to changes in winds driven by global atmospheric circulation patterns, namely the El Niño–Southern Oscillation (ENSO) and Southern Annular Mode (SAM), linking changes in grounded ice to atmospheric-driven ocean warming.

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1/09/2017 : bom.gov.au
Australia in winter 2017

In Brief

Overall, winter national mean temperature very much above average; fifth-warmest on record for winter
Exceptionally warm winter daytime temperatures for Australia
Mean maximum temperature warmest on record nationally, and for Queensland, Western Australia, and the Northern Territory; second-highest for South Australia, and third-highest for New South Wales
Mean minimum temperatures above average nationally, but cooler than average in the southeast, particularly during June
Rainfall very much below average overall; ninth-driest winter on record nationally, tenth-driest for New South Wales and eleventh-driest for Western Australia
June particularly was very dry for the southeast; record low rainfall for Victoria, and second-driest on record nationally

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20/09/2017 : advances.sciencemag.org

Thresholds of catastrophe in the Earth system (Daniel H. Rothman, Lorenz Center, Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. Email: dhr@mit.edu)

Abstract

The history of the Earth system is a story of change. Some changes are gradual and benign, but others, especially those associated with catastrophic mass extinction, are relatively abrupt and destructive. What sets one group apart from the other? Here, I hypothesize that perturbations of Earth’s carbon cycle lead to mass extinction if they exceed either a critical rate at long time scales or a critical size at short time scales. By analyzing 31 carbon isotopic events during the past 542 million years, I identify the critical rate with a limit imposed by mass conservation. Identification of the crossover time scale separating fast from slow events then yields the critical size. The modern critical size for the marine carbon cycle is roughly similar to the mass of carbon that human activities will likely have added to the oceans by the year 2100.

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27/09/2017 : thinkprogress.org/september-heat-wave-noaa
Late-September heat wave leaves climate experts stunned, "Never been a heat wave of this duration and magnitude this late in the season," reports NOAA, by Joe Romm.

Places where temperatures are projected to be within one degree of a record high Wednesday. CREDIT: National Weather Service via WashPost/WeatherBell.com.

[...] in the United States, the current heat wave has set records across the Midwest and East. On Monday, 92ºF was the hottest Burlington, Vermont had ever been that late in the year — by a full seven degrees, the Washington Post reported. On Sunday and Monday, Buffalo, New York saw its latest-ever consecutive 90ºF days. Records for hottest day or hottest series of days this late in the year were crushed in Minneapolis; northern Maine; Ottawa, Canada; and Green Bay, Wisconsin.

The National Weather Service tweeted out a chart showing this very effect.

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27/09/2017 : tropical.atmos.colostate.edu

Real-Time North Atlantic Ocean Statistics by Storm for 2017.

Current season North Atlantic ocean ACE (Compared with 1981-2010 climatology)

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ENSO

28/09/2017 : climate.gov/enso

Sea surface temperatures in the key monitoring region of the tropical Pacific have been dropping through the summer, and a deep pool of cool water is lurking below the surface. NOAA thinks there is a 55-60% chance of La Niña developing this fall and winter.

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Coral Reef Watch

26/09/2017 : coralreefwatch.noaa.gov

This figure shows the regions currently experiencing high levels of heat stress that can cause coral bleaching.

This figure shows the distribution of the lowest heat stress levels predicted by at least 60% of the model ensemble members. In other words, there is a 60% chance that the displayed heat stress levels will occur.

NOAA Coral Reef Watch's satellite Coral Bleaching Alert Area [...] shows the maximum heat stress during the Third Global Coral Bleaching Event. Regions that experienced the high heat stress that can cause coral bleaching, from June 1, 2014 to May 31, 2017, are displayed. Alert Level 2 heat stress indicates widespread coral bleaching and significant mortality. Alert Level 1 heat stress indicates significant coral bleaching. Lower levels of stress may have caused some bleaching as well. More than 70% of coral reefs around the world experienced the heat stress that can cause bleaching and/or mortality during the three-year long global event.

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Climate Prediction Center

28/09/2017 : cpc.ncep.noaa.gov

Global Tropics Benefits/Hazards

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Polar Science Center

28/09/2017 : psc.apl.uw.edu

Arctic sea ice likely reached its minimum extent on September 13 2017 (NSIDC link). Sea ice volume on Sept 15 was 4.5 km³ ,830 km³above the record from Sept. 17, 2012 and the 4th lowest on record. Values for 2011, 2016, 2017 are all within 200 km³. Average ice thickness remains thin, just above minimum September values that occurred in 2010 and 2011. Note that average ice thickness is computed over areas greater than 0.15 m and depends on how much of thin ice remains rather than melts away completely.

Average Arctic sea ice thickness over the ice-covered regions from PIOMAS for a selection of years. The average thickness is calculated for the PIOMAS domain by only including locations where ice is thicker than .15 m.

PIOMAS Ice Thickness Anomaly for August 2017 relative to 2000-2015.

Arctic sea ice volume anomaly from PIOMAS updated once a month. Daily Sea Ice volume anomalies for each day are computed relative to the 1979 to 2016 average for that day of the year. Tickmarks on time axis refer to 1st day of year. The trend for the period 1979- present is shown in blue. Shaded areas show one and two standard deviations from the trend. Error bars indicate the uncertainty of the monthly anomaly plotted once per year.

Total Arctic sea ice volume from PIOMAS showing the volume of the mean annual cycle, and from 2010-2017. Shaded areas indicate one and two standard deviations from the mean.