Abstract. Light absorbing aerosols in the atmosphere and cryosphere play an important role in the climate system. Their presence in ambient air and snow changes the radiative properties of these systems, thus contributing to increased atmospheric warming and snowmelt. High spatio-temporal variability of aerosol concentrations and a shortage of long-term observations contribute to large uncertainties in properly assigning the climate effects of aerosols through time.
Starting around AD1860, many glaciers in the European Alps began to retreat from their maximum mid-19th century terminus positions, thereby visualizing the end of the Little Ice Age in Europe. Radiative forcing by increasing deposition of industrial black carbon to snow has been suggested as the main driver of the abrupt glacier retreats in the Alps. The basis for this hypothesis was model simulations using elemental carbon concentrations at low temporal resolution from two ice cores in the Alps.
by Paul Berth, 21 octobre 2018 in ScienceClimatEnergie
Comme mentionné dans un article précédent, le DMI (Danish Meteorological Institute) publie régulièrement l’évolution temporelle, mois par mois, de l’étendue de la glace de l’Arctique en millions de km2. Le dernier graphique publié (Fig. 1) nous montre l’étendue de la glace au mois de septembre entre 1979 et 2018 (c’est au mois de septembre que l’étendue de glace arctique est la plus faible, moins de 10 millions de km2). Une droite, dont la pente est négative, est tracée parmi les points : tous les 10 ans, la surface semble diminuer de 11,4%. Si l’on extrapole la droite ont peut calculer qu’il n’y aura plus de glace en Arctique dans 60 ans. Cependant, ne remarquez-vous rien d’étrange sur ce graphique?
It is often claimed that modern day sea ice changes are “unprecedented”, alarming, and well outside the range of natural variability. Yet scientists are increasingly finding that biomarker proxies used to reconstruct both Arctic and Antarctic sea ice conditions since the Early Holocene reveal that today’s sea ice changes are not only not unusual, there is more extensive Arctic and Antarctic sea ice during recent decades than there has been for nearly all of the last 10,000 years.
We keep hearing about the Arctic being ice-free anytime from next month up until a continuously rolling forward decade or so. One question that has to be answered is:
What does ice-free mean?
When does ice-free mean ice-free?
First, we need to clarify what exactly an “ice-free” Arctic summer is.
By “ice-free”, scientists usually mean a sea ice extent of less than one million square kilometres, rather than zero sea ice cover.
–Dr Alexandra Jahn, Assistant Professor in the Department of Atmospheric and Oceanic Sciences and Fellow at the Institute of Arctic and Alpine Research at the University of Colorado. Carbon Brief, August 25, 2016.
More than 26,000 years ago, sea level was much lower than it is today partly because the ice sheets that jut out from the continent of Antarctica were enormous and covered by grounded ice — ice that was fully attached to the seafloor. As the planet warmed, the ice sheets melted and contracted, and sea level began to rise. Researchers have discovered new information that illuminates how and when this global phenomenon occurred.
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More recently in 2002, in the northern part of Antarctica called the Antarctic Peninsula, the Larsen Ice Shelf collapsed. The collapse of this ice shelf quickly led to inland glaciers buttressed by the Larsen Ice Shelf to break up and melt. Scientists have thought that a similar process could have occurred when the Ross Ice Shelf collapsed thousands of years ago in the West Antarctic Ice Sheet.
However, Bart and colleagues from the University of South Florida, Auburn University and the Polish Academy of Sciences found that there was a centuries-long delay from when the Ross Ice Shelf collapsed and the grounded ice began to contract. In the Ross Sea, the delay was between 200 to 1,400 years later. This new information adds a layer of complexity for sea level rise computer simulations and predictions.
by Ron Clutz, September 22, 2018 in ScienceMatters
People are overthinking and over-analyzing Arctic Ice extents, and getting wrapped around the axle (or should I say axis). So let’s keep it simple and we can all readily understand what is happening up North.
I will use the ever popular NOAA dataset derived from satellite passive microwave sensors. It sometimes understates the ice extents, but everyone refers to it and it is complete from 1979 to 2017. Here’s what NOAA reports (in M km2):
This article claim ships will “be able to sail right over the North Pole” by 2050 due to warming, but at the same time say ship tracks will make more clouds and cool the Arctic. Of course, anything is possible with the help of climate models.
More ships and more clouds mean cooling in the Arctic
With sea ice in the Arctic melting at an alarming rate, opportunities for trans-Arctic shipping are opening up, and by mid-century ships will be able to sail right over the North Pole – something not previously possible for humankind.
by Ron Clutz, September 17, 2018 in ScienceMatters
One week ago on day 252 MASIE reported the lowest daily extent of the year at 4.43M km2. One week later the image above shows how the ice edges have refrozen and extended. Note also the significant snowfall both in Canada and Russia
by P. Homewood, September 2, 2018 in NotaLotofPeopleKnowThat
Global temperatures fell back to 0.19C in August. This means the YTD average is 0.23C, putting them back to roughly where they were in 2002.
Arctic sea ice is tracking close to 2014, which finished with one of the highest minimums in the last decade. Current extent is well above the last three years.
Malgré des températures particulièrement élevées ces dernières semaines sur l’Hémisphère Nord, voire exceptionnelles sur l’Europe, le déclin des glaces de l’Arctique s’est vu ralenti.
Au 23 août, l’étendue des glaces de l’Arctique était d’approximativement 4.945 millions de kilomètres carrés. Des niveaux toujours particulièrement bas au regard de la moyenne observée sur la période 1981-2010 (6.866 millions de km2, soit un déficit de 28%). Néanmoins, ce niveau n’est « que » le 6e plus bas observé à cette date, très loin de la triste année 2012 (une superficie inférieure à 4 millions de km2 à la fin août). Une timide amélioration, puisque l’étendue de ces glaces avait alors été la 4e plus faible jamais observée sur l’ensemble du mois de juin.
Graphique de l’étendue des glaces de l’océan Arctique (en millions de km2) – Zachary Michael Labe
by Tony Heller, August 31, 2018 in ClimateChangeDispatch
Summer is over, and Greenland’s surface has gained 510 billion tons of ice over the past year – about 40% above normal. The surface mass budget is snow/ice accumulation minus melt.
As the Arctic summer ice melt approaches its peak, we can say with high certainty that this year’s ice melt will extend the trend of a rebounding Arctic ice mass by another year.
Arctic summer sea ice now growing 12 years
Our Japanese skeptic blogger and good friend Kirye reports using the data from the Danish Meteorological Institute (DMI) that peak summer Arctic sea ice volume upward growth trend has been extended yet another year – now 12 years.
Chart by Kirye. Data source: Danish Meteorology Institute (DMI).
Using data from the Danish Meteorological Institute (DMI), Japanese skeptic blogger Kirye just tweeted how Arctic sea ice volume has surged to the 3rd highest level in 16 years.
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Data source. Danish Meteorological Institute. Chart source: Kirye.
Recently climate catastrophe non-believers have been pointing out that Arctic sea ice volume has been gaining over the past years and has not trended downward for some dozen years now.
And global warming alarmists have been very silent on the subject of climate change now that global surface temperatures have cooled and Arctic and Greenland snow and ice have rebounded.
Embarrassed, they don’t want to be reminded of all the absurd predictions they made 10 years ago, with some as recently as just five years ago.
Lately Arctic sea ice volume has been a topic which climate skeptics have been looking at quite closely.
According to Al Gore and a number of climate ambulance chasers, Arctic sea ice in late summer should have long disappeared by now, see here..
But then just a few years after, the Arctic sea ice area began to recover from its lows of 2007 and 2012. So immediately alarmists shouted that area was not really what mattered, but rather sea ice volume is what really counted. Okay, that made perfect sense. Mass is in fact what’s important, and not area, when worrying about polar ice disappearing …
German climate and weather analyst “Schneefan” (Snow Fan) here writes a summary of the first half of 2018 thus far. All data show that the surface temperature of the globe has been cooling strongly over the past months and polar ice mass growing.
He writes that in the first half of this year we have seen weak solar activity and La Nina conditions acting to cool the globe’s surface. Moreover Arctic and Antarctic ice mass have grown in comparison to the previous years. …
by M. Bastach, June 28, 2018 in ClimateChangeDispatch
A group of scientists at the University of Rhode Island stumbled on something unexpected when analyzing data brought back from a 2014 expedition to western Antarctica.
Scientists found an abundance of the noble gas Helium-3, indicating there is a volcanic heat source beneath the Pine Island glacier — the fastest melting glacier in the South Pole. The findings were published in a study in the journal Nature Communications.
“When you find helium-3, it’s like a fingerprint for volcanism. We found that it is relatively abundant in the seawater at the Pine Island shelf,” chemical oceanographer Brice Loose, the study’s lead author, said in a statement.
See also here (National Science Foundation) and here
Antarctic ice sheet is melting, but rising bedrock below could slow it down
An international team, led by DTU Space at the Technical University of Denmark with Colorado State University, has found that the bedrock below the remote West Antarctic Ice Sheet is rising much more rapidly than previously thought, in response to ongoing ice melt.
The study, “Observed rapid bedrock uplift in the Amundsen Sea Embayment promotes ice-sheet stability,” reveals new insights on the geology of the region and its interaction with the ice sheet and is published in the journal Science. The authors noted that the findings have important implications in understanding and predicting the stability of the ice sheet and Earth’s rising sea levels.
According to a new paper published in the Journal of Geophysical Research, the observed mean thickness of the sea ice in the region north of (Arctic) Svalbard was substantially thinner (0.94 m) in 1955 than it has been in recent years (~1.6 m, 2015/2017).
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La géologie, une science plus que passionnante … et diverse
