8 rasterized nautical charts added & 106 charts updated
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Tuesday, October 22, 2019
Ocean acidification can cause mass extinctions, fossils reveal
Heterohelix globulosa foraminifera isolated from the K-Pg boundary clay at Geulhemmerberg in the Netherlands, shown at 8x magnification.
Study confirms fear that intense ocean acidification portends ecological catastrophe: ‘We have been warned’
Study confirms fear that intense ocean acidification portends ecological catastrophe: ‘We have been warned’
Photograph: Michael J. Henehan/PNAS
From The Guardian
Carbon emissions make sea more acidic, which wiped out 75% of marine species 66m years ago
Ocean acidification can cause the mass extinction of marine life, fossil evidence from 66m years ago has revealed.
A key impact of today’s climate crisis is that seas are again getting more acidic, as they absorb carbon emissions from the burning of coal, oil and gas.
Scientists said the latest research is a warning that humanity is risking potential “ecological collapse” in the oceans, which produce half the oxygen we breathe.
The researchers analysed small seashells in sediment laid down shortly after a giant meteorite hit the Earth, wiping out the dinosaurs and three-quarters of marine species.
Chemical analysis of the shells showed a sharp drop in the pH of the ocean in the century to the millennium after the strike.
This spike demonstrated it was the meteorite impact that made the ocean more acidic, effectively dissolving the chalky shells of many species.
Large-scale volcanic activity was also considered a possible culprit, but this occurred over a much longer period.
The Cretaceous-Palaeogene boundary at Geulhemmerberg, in the Netherlands, where boundary clay samples were taken.
credit : Michael Henehan
The oceans acidified because the meteorite impact vaporised rocks containing sulphates and carbonates, causing sulphuric acid and carbonic acid to rain down.
The mass die-off of plants on land after the strike also increased CO2 in the atmosphere.
“We show ocean acidification can precipitate ecological collapse,” said Michael Henehan at the GFZ German research centre for geosciences in Potsdam, who led the study.
“Before we had the idea, but we did not have the empirical proof.”
The researchers found that the pH dropped by 0.25 pH units in the 100-1,000 years after the strike.
It is possible that there was an even bigger drop in pH in the decade or two after the strike and the scientists are examining other sediments in even finer detail.
Henehan said: “If 0.25 was enough to precipitate a mass extinction, we should be worried.” Researchers estimate that the pH of the ocean will drop by 0.4 pH units by the end of this century if carbon emissions are not stopped, or by 0.15 units if global temperature rise is limited to 2C.
Henehan said: “We may think of [acidification] as something to worry about for our grandchildren.
But if it truly does get to the same acidification as at the [meteorite strike] boundary, then you are talking about effects that will last for the lifetime of our species.
It was hundreds of thousands of years before carbon cycling returned to normal.”
The research, published in the journal Proceedings of the National Academy of Sciences, analysed sediments that Henehan encountered by chance, during a conference field trip in the Netherlands.
The sediments, which straddle the moment of the impact, lie in caves that were used by people hiding from the Nazis during the second world war.
“It was so lucky,” said Henehan.
The rocks contained foraminifera, small-shelled marine organisms.
“In the boundary clay, we managed to capture them just limping on past the asteroid impact.
But you can see their shell walls were much thinner and poorly calcified after the impact,” he said.
It was the knock-on effects of acidification and other stresses, such as the “nuclear winter” that followed the impact, that finally drove these foraminifera to extinction, he said: “You have the complete breakdown of the whole food chain.”
He said oceans also faced additional stresses today, from global heating to widespread pollution, overfishing and invasive alien species.
When the Chicxulub asteroid landed in what is today Mexico, it didn't just extinguish the dinosaurs. It devastated life in the oceans, too.
Phil Williamson, at the University of East Anglia, who was not involved in the research, said: “It is relatively easy to identify mass extinction events in the fossil record, but much harder to know exactly what caused them. Evidence for the role of ocean acidification has generally been weak, until now.”
He said caution was needed in making the comparison between the acidification spike 66m years ago and today: “When the asteroid struck, atmospheric CO2 was naturally already much higher than today, and the pH much lower.
Furthermore, large asteroid impacts cause prolonged darkness.”
Williamson added: “Nevertheless, this study provides further warning that the global changes in ocean chemistry that we are currently driving have the potential to cause highly undesirable and effectively irreversible damage to ocean biology.”
Henehan said the generally lower ocean pH 66m years ago might have made shelled organisms more resilient to acidification.
“Who knows if our current [marine] system is as well set up to cope with sudden acidification?”
Links :
- YaleNews : Mystery solved: ocean acidity in the last mass extinction
- CNN : Tiny shell fossils reveal how ocean acidification can cause ...
- NYTimes : The Dinosaur-Killing Asteroid Acidified the Ocean in a Flash
- Oceanographic Mag : Study reveals ocean acidification has caused mass extinctions
- Phys : Mystery solved: Ocean acidity in the last mass extinction
- CNET : Dinosaur-killing asteroid rapidly turned oceans to acid, disrupted climate
- Yale : Farmed Oysters Show Resilience to Ocean Acidification
- Hawaï News : Climate Change, Explained: What is ocean acidification?
- GeoGarage blog : Ocean acidification is deadly threat to ... / 'The other CO2 problem': How acidic oceans .. / Satellite images to monitor ocean acidification in remote areas ... / The seafloor is dissolving, thanks to human ... / An acid test for policy / Study: our oceans are so acidic they're ...
Monday, October 21, 2019
Croatia (HHI) update in the GeoGarage platform
25 new nautical rasterized charts added & 58 charts updated
see GeoGarage news
On May 22., 2019. for the official use of 25 new
cells of electronic navigation Cards (ENC).
Thus, the Croatian
Hydrographic Institute (HHI) enabled availability and use of a total of
207 cells of enc all upotrebnih groups, which announces with special
pleasure and pride.
The first package of enc's hhi was issued
12 years ago (February 2007.), and for priority areas intended for
sailing very fast boats (High Speed Craft).
He continued to release new
packages according to established priorities, leading the criteria to
ensure the coverage of the most important areas of the solas ships in
the international
After the complete coverage of the plovidbenih area of
solas ships, hhi continues to create and publish new enc for areas of
smaller ports and sailing smaller boats (Non-Solas) and yachts.
By establishing production and distribution of official enc, hhi has
greatly contributed to the improvement of the hydrographic-navigation
element of safety, which has been fulfilled and internationally
downloaded the obligation of ensuring the availability of enc on ships
to a certain deadline, and for the area of the
Information
about all the published cells of enc is available to users in the print
edition of the catalogue of maritime cards and publications, as well as
on the website of hhi -
25 New Electronic Navigation Charts (ENC) Released
On July 17, 2019, 25 new electronic navigation charts (ENCs) were issued for official use.
This enabled the Croatian Hydrographic Institute (HHI) to make available and use a total of 232 ENC cells of all use groups.
Official electronic charts can be obtained through the regional coordinating center PRIMAR and its network of authorized distributors.
Information on all published ENC cells is available in the printed edition of the Catalog of Maritime Maps and Publications as well as on the HHI website
Satellites to monitor whale strandings from space
Dr Jennifer Jackson: "Satellites get us to whales in those places that are hard to reach"
From BBC by Jonathan Amos
Scientists developing techniques to count great whales from space say the largest ever recorded mass stranding event was probably underestimated.
The carcasses of 343 sei whales were spotted on remote beaches in Patagonia, Chile, in 2015 - but this survey work was conducted from planes and boats, and carried out many weeks after the deaths actually occurred.
However, an analysis of high-resolution satellite images of the area taken much closer in time to the stranding has now identified many more bodies.
It's difficult to give a precise total for the number of whales involved but in one sample picture examined by researchers, the count was nearly double.
The new investigation, published in the Plos One journal, was undertaken as a proof of principle exercise by the British Antarctic Survey (BAS) and various Chilean organisations.
The WorldView-2 satellite will see features at the surface larger than
half a metre across
Image copyright Satellite image ©2019 Maxar Technologies
Image copyright Satellite image ©2019 Maxar Technologies
It's not easy to see an object, even one as large as a great whale, from several hundred kilometres up in space, but the international team believes the capability of modern satellites now makes this a practical task.
Being able to detect strandings more effectively will inform the ongoing conservation of whales.
It will also flag potentially deteriorating ocean conditions, something the fishing industry for example will be keen to know about.
The monitoring of whales from orbit is set therefore to become a powerful tool with which to assess the state of the environment.
"The technology is getting better all the time," said Dr Carlos Olavarría from the Centre for Advanced Studies in Arid Zones (CEAZA), La Serena, Chile.
"In this study, we were using 50cm resolution images, but the satellites now can see 30cm. In the future, we'd like also to be able to analyse the pictures automatically, rather than manually; and I'm sure as more minds are applied to the problem, this will become possible," he told BBC News.
Aerial survey image of stranded whales
Photo: Hausermann/BAS
What happened in the stranding event?
It's not clear why such a large number of sei whales beached en masse in early 2015.
One reason for the uncertainty is that researchers were very late in getting to the scene to run tests to establish the cause.
That was in part because the stranding occurred in a very thinly populated, and difficult to access, area of central Patagonia called the Gulf of Penas.
It has multiple fjords, channels and islands, and the deaths only came to light by accident when an unrelated expedition chanced on the carcasses.
This was a good month after the event and by then the sei whales had already started to decompose. Nonetheless, a ground team's inquiries led it to the conclusion that the cetaceans had probably been poisoned after consuming toxic algae.
Image copyright Satellite image ©2019 Maxar Technologies
Image caption The animals turn a pinkish orange when they decompose (Scale bar: 20m)
How did the satellites gauge the event's size?
The planes and boats that surveyed the Gulf of Penas counted more than 340 dead whales, but the complex geography meant that some bodies almost certainly were missed.
"The aerial survey was done on a huge scale and was very impressive, but it's possible some of the carcasses got washed back out to sea in storms and simply weren't counted. The 343 number was only ever a best estimate," said BAS whale expert Dr Jennifer Jackson.
The high-resolution satellite imagery allowed scientists to do a count much closer in time to the event itself.
The researchers used pictures from the WorldView-2 spacecraft which can discern features larger than 50cm across from an altitude of 700km.
For a whale that may be 10-15m in length, this produces a good outline of the animal's overall shape, including its distinctive fluke.
The team examined two archive images of the gulf from mid-March in 2015.
In one, they counted slightly fewer whales than in the aerial survey work; but substantially more in the second picture.
Image copyright V.Haussermann
Image caption The aerial survey was conducted many weeks after the event actually happened
So, how useful is satellite observation?
It's possible to see the big baleen whales, like the sei whale, from orbit, and with the WorldView series of satellites now offering 30cm resolution, the task should become even easier - and for smaller whale species too, not just the baleens.
Scientists could monitor any beach in world, but especially those remote coastlines where cetacean strandings are a regular occurrence - in places such as Tasmania, New Zealand, the Falkland Islands, and obviously South American Patagonia.
But it would be even easier if an automated detection system could be developed. The team tried this by training a computer to look for the spectral (light) signature of a dead whale in the Gulf of Penas (the seis turned pink and orange as they decomposed).
However, this approach was less successful than manual inspection of the pictures. The algorithms, though, are bound to improve.
"There are many more satellites planned to be launched with 50cm and 30cm resolution, so if we could automate the system it might be able to find these stranding events almost as they happen," BAS remote sensing specialist Peter Fretwell told BBC News.
Media captionZoom in to the Gulf of Penas
(satellite image ©2019 Maxar Technologies)
(satellite image ©2019 Maxar Technologies)
How will whales benefit from this science?
Getting to the scene of a stranding quickly will give greater certainty to the cause of an event.
Sei whales have continued to wash up in the Gulf of Penas every year since 2015 and so it's vital scientists understand fully what's happening off-shore.
Strandings more widely can be useful markers of the status of a population.
The dissection of washed-up bodies (a necropsy) will be an opportunity to investigate the general health of animals, and to study aspects of their behaviour such as their dietary habits.
Even just the pattern of strandings will provide information on which whales are present in an area and their likely numbers.
All this detail is facilitated by a more rapid response.
"It's important ecologically," commented Andrew Baillie, the Cetacean Strandings Officer at London's Natural History Museum.
"[Whales] are often top predators and they are very involved in the marine ecosystem. If they are suffering because of any actions of humans then we need to monitor that and mitigate it if possible."
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