1200 letna mini ledena doba

NEWS CLIMATE 31 JANUARY 2018

1200 letna mini ledena doba je povzročila globalno segrevanje

Izotopska analiza razkriva podroben vzorec antičnega vremenskega dogodka in sproži opozorila o ponovitvi, poroča Richard A Lovett

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In led se je vrnil: Analiza izotopov ledu kaže, da je bilo globalno segrevanje odgovorno za 1200 let hladnega podnebja že v preteklosti.

Geologi, ki preučujejo gramoz, ki jih je ostal kot posledica taljenja starodavnih kanadskih ledenih plošč in potrjujejo teorijo, da je hladno obdobje, ki se imenuje mlajša ledena doba v 1200-letni zgodovine na Severni polobli, ironično povzročilo globalno segrevanje.

Mlajši ledena doba je trajala od približno 12.900 do pred 11.700 leti in imela povprečno temperaturo v severovzhodni Severni Ameriki, Evropi in Grenlandiji nižjo za neverjetnih 10 stopinj Celzija.

"[To je bil] oster preobrat nazaj k skoraj polnim pogojem ledene dobe," pravi Andy Wickert, geolog na Univerzi v Minnesoti v ZDA, ki ni član ekipe, ki je pripravljala nove študije.

Ena od teorij je, da je recesijo povzročil asteroidni ali kometni učinek, ki je napolnil ozračje z meglico, kar je zmanjšalo količino sončne svetlobe, ki je dosegla površino. Ampak ni jasno, kako bi to lahko povzročilo tako dolgotrajno hlajenje. Bolj popularna teorija je ta, da jo je povzročil dotok velikih količin sveže vode v Severni Atlantik.

Vprašanje se imenuje Severnoatlantski termohalinska cirkulacija, v katerem tokovi, kot je zalivski tok, prenašajo tople vode bolj severno, kot so Kanada, Islandija, Združeno kraljestvo in celo Norveška. Vzdolž poti, mrzla vode postaja gostejša, dokler ne potone in jo nadomesti bolj topla voda z juga. Proces je pomemben mehanizem za črpanje toplote severno od tropskih območij in glavni razlog, zakaj je Norveška toplejša od Sibirije.

Toda sladka voda je približno 2,5% manj gosta od morske vode. Dovolj velik dotok sladke vode v Severni Atlantik bi povzročil, da bi površinska voda potonila v globino, pod slano vodo, kljub temu, da je mrzla. Richard Alley, znanstvenik geologije na Državni univerzi Pennsylvania, Univerza Park, ga primerja z vstavljanjem izvijača v transportni trak v trenutku, ko gre navzdol, ter ga nenadoma ustavi.

"To ni popolna analogija," pravi, "ampak če vrinete dovolj sladke, hladne vode v [Severni Atlantik] v poletnih mesecih, bo voda v oceanu naslednjo zimo zamrznila, in boste imeli učinek podhladitve " pravi.

To je v resnici bila zamisel za film "Dan po jutrišnjem" leta 2004, čeprav je film močno pretiraval o znanosti tako ,da se je večina znanstvenikov na tem področju pridružila kritikom.

V novi študiji, ki je bila objavljena na spletu v reviji Geology, so raziskovalci našli pot, po kateri bi velika reka lahko v pravem trenutku prinesla ogromne količine vode v Severni Atlantik, da bi sprožila hladnejše manjše ledene dobe.

Voda bi izhajala iz ogromnega jezera, imenovanega jezero Agassiz, ki se je v različnih časih širilo po velikih odsekih kanadskih pokrajin Manitoba, Saskatchewan in Ontario. Pred zadnjo manjšo ledeno dobo se je usmerila na jug, v ameriško reko Mississippi in od tam v Mehiški zaliv, kjer je njen vpliv na podnebje minimalen.

Toda na podlagi sledov v izotopih v granitnem grušču so znanstveniki dokazali, da se je novi kanal odprl proti vzhodu ob pravem času, da bi sprožil manjšo ledeno dobo z vodo, ki je pritekala po sedanjih Velikih jezerih v Severni Atlantik preko Kandske reke Saint Lawrence.

Najdba, pravi avtor študije Anders Carlson, glacialni geolog na Oregonski državni univerzi, Corvallis, izhaja iz uporabe berilija-10,s katerim so izmerili, kdaj so ti balvani pod ledom nastali..

Berilij-10 se oblikuje z bombardiranjem kozmičnih žarkov, ki ga ustvarja v kremenastih zrn s hitrostjo približno štiri do pet atomov na gram, na leto, pravi Carlson. Z merjenjem količine v balvanih, ki jih je ledena ploščica izkopala iz ledu, in jih je z ledom povleklo proti jugu, nato pa so pokopali pod tisoče metrov debelim ledom, dokler se ni stopil. Pravi, da je mogoče točno ugotoviti, kdaj so se te kamnine pojavile na dnevni svetlobi.

How a 'little' ice age shaped civilisation

PODNEBJE

Primerja ga z merjenjem količine sončnih in kozmičnih žarkov (spaceburn) žarkov, ki so jo nakopičili ti kamni, ko so se prvič pojavili - čeprav večina kozmičnih žarkov prihaja iz virov, ki niso sončni, je "spaceburn" verjetno bolj natančen izraz. Kakorkoli, "lahko neposredno datiramo z umikom ledu," pravi.

Odkrivanje vzroka 12 000-letne podnebne spremembe se morda ne zdi toliko pomembno, vendar je res, da smo v dobi segrevanja, v katerem se led ponovno hitro topi. Da bi dobili ekvivalentno sladkovodno praznjenje v Severni Atlantik, pravi Carlson, bi se ledena plošča iz Grenlandije v približno 1300 letih morala popolnoma stopiti."To je verjetno," pravi Carlson. "To je veliko segrevanja, vendar ni izven področja možnosti."

In medtem ko je bila mlajša ledena doba fenomen severne poloble, so se isti dejavniki, ki so zadrževali toploto pred selitvijo na sever povzročili, da se je na jugu razvil pojav, ko so se "Ledeniki v Novozelandskih Alpah umaknili," pravi Carlson. Da ne omenjam, da bi hlajenje na skrajnem severu lahko premaknilo monsun. "Njegov normalni položaj je rahlo severno od ekvatorja," pravi Carlson, "ampak če ohladite severno poloblo, lahko povprečni monsunski pas premaknete na jug."

1200-year mini Ice Age

NEWS CLIMATE 31 JANUARY 2018

1200-year mini Ice Age was caused by global warming

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Isotope analysis reveals detailed pattern of ancient weather event, and prompts warnings of a repeat. Richard A Lovett reports.

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And the ice came back: Isotope analysis suggests global warming was responsible for a 1200-year cold snap.

Geologists studying boulders left behind by the melting of ancient Canadian ice sheets are confirming a theory that a 1200-year-long Northern Hemisphere cold snap called the Younger Dryas was, ironically, caused by global warming.

The Younger Dryas lasted from about 12,900 until 11,700 years ago and saw temperatures in northeastern North America, Europe, and Greenland drop by a whopping 10 degrees Celsius.

“[It was] a sharp reversal back toward nearly full Ice Age conditions,” says Andy Wickert, a geologist at the University of Minnesota in the US, who was not part of the new study.

One theory is that the downturn was caused by an asteroid or comet impact that filled the atmosphere with haze, reducing the amount of sunlight reaching the surface. But it’s not clear how that could have caused such a prolonged cooling. A more popular theory is that it was caused by the influx of large amounts of fresh water into the North Atlantic.

At issue is something called the North Atlantic thermohaline circulation, in which currents such as the Gulf Stream carry warm water from the topics as far north as Canada, Iceland, the UK, and even Norway. Along the way, the water chills, becoming denser, until it sinks and is replaced by more warm water from the south. The process is an important mechanism for drawing heat northward from the tropics, and a major reason why Norway is warmer than Siberia.

But fresh water is about 2.5% less dense than seawater. A large enough influx of it into the North Atlantic would throw a major spanner into the works by preventing the surface water from sinking into higher-saline depths as it chills. Richard Alley, a geoscientist at Pennsylvania State University, University Park, compares it to jamming a screwdriver into a grocery-store conveyor belt at the point where it goes down, bringing it to a sudden halt. 

“It isn’t a perfect analogy,” he says, “but if you dump enough water into [the North Atlantic] in the summer, the water will cap the ocean the next winter, freeze, and you will have a cold event,” he says.

(This, in fact, was the idea behind the 2004 movie The Day After Tomorrow, although the movie sufficiently exaggerated the science that most scientists in the field joined the critics in calling it dreadful.)

In the new study, published online in the journal Geology, the researchers found a route by which a large river could have dumped massive amounts of water into the North Atlantic at just the right time to trigger the Younger Dryas cold snap.

The water would have come from an enormous lake, called Lake Agassiz, which at various times sprawled across large swaths of the Canadian provinces of Manitoba, Saskatchewan, and Ontario. Prior to the Younger Dryas, it drained south, into America’s Mississippi river and from there into the Gulf of Mexico, where its effect on climate would have been minimal.

But based on trace isotopes in granite boulders, the scientists showed that a new channel opened to the eastward at just the right time to trigger the Younger Dryas, with the water running through the modern-day Great Lakes and out to the North Atlantic via Canada’s Saint Lawrence River.

The find, says study author Anders Carlson, a glacial geologist at Oregon State University, Corvallis, came from using beryllium-10 to measure how long ago these boulders first emerged from beneath the ice.

Beryllium-10 is formed by cosmic ray bombardment, which creates it in quartz grains, at a rate of about four to five atoms per gram, per year, Carlson says. By measuring the amount in boulders that had been plucked out of bedrock by the ice sheet, dragged south by the ice, then shielded by thousands of metres of it until it melted, he says, it’s possible to determine when these rocks first emerged into the daylight.

How a 'little' ice age shaped civilisation

CLIMATE

He compares it to measuring the amount of sunburn accumulated by these rocks since they first came to light – although, since most cosmic rays come from sources other than the sun, “spaceburn” is probably a more accurate term. Either way, “we can directly date the ice retreat,” he says.

Figuring out the cause of a 12,000-year-old climate change may not seem all that important, but the reality is that we’re in another era of warming, in which ice is again rapidly melting. To get an equivalent freshwater discharge into the North Atlantic, Carlson says, the Greenland ice sheet would need to entirely melt in about 1300 years.

“That is plausible,” Carlson says. “It’s a lot of warming, but it’s not out of the realm of possibility.”

And while the Younger Dryas cold snap was a Northern Hemisphere phenomenon, the same factors that kept heat from moving north caused it to build up in the south. “Glaciers in the New Zealand Alps retreated,” Carlson says.

Not to mention that cooling in the far north could shift the monsoon.

“Its normal position is slightly north of the Equator,” Carlson says, “but if you cool the Northern Hemisphere, you could shift the average monsoon belt south.”

Zemljina magnetna pola

Znanost

Zemljina magnetna pola kažeta znake, da bi se lahko zamenjala, s čimer bi bili ljudje izpostavljeni radiacijskim napadom

Zgodovinsko gledano se zemeljski severni in južni magnetni pol zamenjata vsakih 200.000 ali 300.000 let, razen sedaj, ko se nista uspešno zamenjala že približno 780.000 let. Toda magnetno polje planeta že končno kaže znake premika. Čeprav ni mogoče vedeti zagotovo, pa bi se lahko po poročanju revije Undark, ponovno zamenjala. In ta možnost vzbuja nove špekulacije o tem, kaj to pomeni za planetarno življenje.

Magnetno polje našega planeta nas ščiti pred smrtonosnimi ravnmi sevanja zaradi pojavov, kot so sončni žarki. Nevarni delci nas nikoli niso udarili neposredno, ker jih po vstopu v zemeljsko atmosfero magnetno polje ( ^{1- opis spodaj}) odkloni in prisili, da se premikajo ( po NASA) . Zato je zaskrbljujoče, da se to polje slabi, kar počne, ko se pripravlja na zamenjavo, ter bi nas tako pustilo brez

zadostne zaščite.

Severni magnetni pol Zemlje je od leta 1970 do danes krožil, kot je razvidno iz te animacije nacionalnih centrov za okoljske informacije. (NOAA)

Zemljino magnetno polje se ustvarja iz električnih tokov, ki jih ustvarijo kovine v jedru in ustvarjajo nevidne črte, ki se dotikajo na nasprotnih magnetnih polih planeta. Strokovnjak za kozmično sevanje Daniel Baker, direktor laboratorija za atmosfero in vesoljsko fiziko na Univerzi Colorado, Boulder, verjame, da bi lahko naslednje obračanje pola verjetno nekatera območja na planetu popolnoma onesposobil za življenje. (po mnenju Undark)

Ta uničenja bi lahko prišla na več načinov. Kombinacija močnih vesoljskih delcev, kot so nefiltrirani sončni žarki, kozmični žarki in ultravijolični B žarki (stvari, o katerih vas opozarja vaša steklenica za sončenje), bi se razbil skozi našo uničeno ozonsko plast in nas pripeljali na pot dinozavrov.

Naša infrastruktura ne bi bila nič na boljšem. Ker so satelitske mreže povezane, in ko jih sevanje preči, bi sledilo še več sesutja sistemov (internet, električna omrežja, telefonija, TV, bančništvo....), kar bi povzročilo kaskadno masovno uničenje, med drugimi nesrečami, seveda.

Ker še nismo dosegli te točke, znanstveniki uporabljajo slike satelitov, da bi spremljali premike magnetnega polja. Od leta 2014 je Swarm-trio satelitov Evropske vesoljske agencije omogočil raziskovalcem, da preučujejo spremembe, ki se gradijo v Zemljinem jedru, kjer se ustvarja magnetno polje.

Zgodovinsko gledano sta se zemeljski severni in južni magnetni pol zamenjala vsakih 200.000 ali 300.000 let, razen sedaj. Toda planetovo magnetno polje že dolgo kaže znake premikanja, tako NASA.

Njihove ugotovitve kažejo, da se talini železo in nikelj izlivata iz jedra Zemlje. Takšna nemirna dejavnost bi lahko kazala, da se polje pripravlja na obrat, v skladu s Undarkom. Zaščitni ukrepi bi lahko vključevali izgradnjo več satelitov, ki bi bili obogateni s sevanjem, in dogradnjo tistih, ki že delujejo.

Niso bili vsi poskusi zamenjave zemeljske polarnosti uspešni; zadnjič pred nekaj več kot 40.000 leti, se je po mnenju "Futurizma" zrušil, ustavil. In znanstveniki morajo še ugotoviti vzročno-posledično povezavo med obračanjem polovin množičnimi izumrtji.

Morda res ne vemo, kdaj bosta pola končno dokončala svojo predvideno dolgoročno obračanje, vendar imamo vsaj to prednost, da se nanj lahko pripravimo.

Magnetno  polje

Fizika

Magnetni pol, regija na vsakem koncu magneta, kjer je zunanje magnetno polje najmočnejše. Magnet, ki je prisoten v zemeljskem magnetnem polju, se usmeri v smeri sever-jug. Severni magnet se imenuje severni magnetni pol. Južni iskalni pol ali kateri koli pol, ki je podoben temu, se imenuje južni magnetni pol. Kot poli različnih magnetov privlačijo drug drugega; se enaki poli odbijajo drug drugega. (privlačita se severni in južni, odbijata se dva severna itd)

Earth’s Magnetic Poles Show Signs They’re About to Flip

Science

Earth’s Magnetic Poles Show Signs They’re About to Flip—Exposing Humans to Radiation and Planet-Wide Blackouts

Historically, Earth’s North and South magnetic poles have flipped every 200,000 or 300,000 years—except right now, they haven’t flipped successfully for about 780,000 years. But the planet’s magnetic field is at long last showing signs of shifting. Although there’s no way to know yet for sure, it could be gearing up to flip once more, according to Undark Magazine. And that possibility is raising new speculation about what that means for planetary life. 

Our planet’s magnetic field protects us from lethal levels of radiation from phenomena like solar rays. The dangerous particles never hit us directly, because upon entering the Earth’s atmosphere the magnetic field deflects them and forces them to move around, according to NASA. So the prospect of that field weakening, which it does when it’s getting ready to flip, is worrisome: It would leave us without sufficient protection.

The Earth’s North magnetic pole has been wandering at 10-year intervals from 1970 to 2020, as seen in this animation from the National Centers for Environmental Information. NOAA National Centers for Environmental Information

The Earth’s magnetic field extends out from electrical currents created by the metals in its core, generating invisible lines that touch back down at the planet’s opposing magnetic poles. Cosmic radiation expert Daniel Baker, director of the Laboratory for Atmospheric and Space Physics at the University of Colorado, Boulder, believes that the next pole reversal could likely render some areas of the planet unlivable, according to Undark.

That devastation could arrive through multiple avenues. The combination of powerful space particles, like unfiltered solar rays, cosmic rays and ultraviolet B rays (the stuff your sunscreen bottle warns you about), would smash through our battered ozone layer and lead us the way of the dinosaurs.

Our infrastructure wouldn’t fare much better. Since satellite grids are linked, once radiation eats through, more will follow, causing a cascading mass blackout, among other disasters, according to Undark.

Because we haven’t reached that point yet, scientists are using imagery from satellites to track the magnetic field’s movements. Since 2014, Swarm—a trio of satellites from the European Space Agency—has allowed researchers to study changes building at the Earth’s core, where the magnetic field is generated. 

Historically, Earth’s North and South magnetic poles have flipped every 200,000 or 300,000 years—except right now, they haven’t flipped successfully for about 780,000 years. But the planet’s magnetic field is at long last showing signs of shifting.NASA

Their observations reveal that both the molten iron and nickel are draining out of the Earth’s core. That kind of restless activity could indicate that the field is preparing to flip, according to Undark. Protective measures could include building more radiation-fortified satellites, plus shoring up ones that are already operational, according to the International Business Times.

Not all of the Earth’s polarity reversal attempts are successful; the poles last put out a botched effort around 40,000 years ago, according to Futurism. And scientists have yet to establish a cause-and-effect relationship between pole reversals and mass extinctions.

But that doesn’t mean there isn’t one. We might not know when the poles will finally complete their long-overdue switch, but we at least have the advantage of being able to prepare.

Orion, dom Bogov

ANCIENT HISTORY

Tu je vaša priložnost za potovanje skozi ozvezdja Orion; Dom Bogov.

Ozvezdje Orion je ena najbolj opaznih zvezd na nočnem nebu. Že tisočletja so stari ljudi šteli to mesto na nebu za izredno pomembnega, saj je bilo mišljeno, da so od tam prišli bogovi ustvarjalcev človeštva in civilizacije na Zemlji. Ozvezdje Orion je imelo poseben položaj ne samo v mitologiji po vsem svetu, ampak tudi v zgodovini in življenjskem slogu skozi tisočletja.

Meglica Orion, znana tudi pod imenom Messier 42, M42 ali NGC 1976, je razpršena meglica, ki leži južno od pasu Orion. Je ena od najsvetlejših meglic, ki obstajajo in je ena redkih, ki jo lahko vidimo s prostim očesom na nočnem nebu. Od Zemlje se nahaja približno 1270 svetlobnih let in ima premer približno 24 svetlobnih let.

Meglica Orion svet na tej VLT sliki Survey Telescope image. ESO/G. Beccari

Zdaj so astronomi in strokovnjaki za vizualizacijo iz programa NASA Universe of Learning ustvarili spektakularen tridimenzionalni film o meglici Orion, kozmičnem zvezdnem vrtincu.

S pomočjo vidnih in infrardečih kamer na vesoljskih teleskopih Hubble in Spitzer skupaj s hollywoodskimi tehnikami je ekipa z vesoljskega teleskopa Science Institute v Baltimoru, Maryland in Caltech / IPAC v Pasadeni v Kaliforniji izdelala najboljše in najbolj podrobne vizualizacija več valovnih dolžin Orionove meglice.

Cilj je ustvariti novo generacijo programov in izkušenj, ki jih je razvil program NASA Universe of Learning, ki omogoča ne samo znanstvenikom, temveč širši javnosti, da razišče temeljna vprašanja v znanosti, doživlja, kako se izvaja znanost in odkrijejo vesolje tudi zase..

"Zmožnost letenja skozi meglico v treh dimenzijah daje ljudem veliko boljši občutek, kako vesolje resnično izgleda," je povedal znanstvenik Frankfurta Summersa iz znanstvenega inštituta Space Telescope Science Institute, ki je vodil ekipo, ki je razvila film.

"Z dodajanjem globine in strukture neverjetnim slikam to letenje pomaga razkriti vesolje za javnost, tako za izobraževanje kot navdih," je dodal Summer.

Triminutni film omogoča gledalcem, da se plazijo skozi slikovito regijo, ki oblikuje ozvezdje, in vesoljsko doživetje poživi na nov in razburljiv način, skupaj z NASA.

"Pogled v vesolje v infrardeči svetlobi daje presenetljiv kontekst za bolj nam domače vidne oblike. Ta film ponuja edinstveno in izjemno priložnost, da vidimo, kako se pojavijo nove značilnosti, ko se premikamo na valovne dolžine svetlobe, ki je običajno nevidna za naše oči, "je povedal Robert Hurt, vodja vizualizacije na IPAC.

Tukaj je video, ENJOY

https://youtu.be/xCFg5udYbAg

vir:  NASA Space Telescopes Provide a 3D Journey Through the Orion Nebula

Orion, home of Gods

ANCIENT HISTORY

Here’s Your Chance To Travel Through The Constellation Of Orion; Home Of The Gods

The Constellation of Orion is one of the most observed stars in the night sky. For millennia have ancient people considered this place in the sky of extreme importance, since, it was thought that from there mankind’s creator gods arrived, kickstarting civilization on Earth.

The Constellation of Orion held a special place not only in Mythologies around the world but in history and lifestyle as well.

The Orion Nebula, also known as Messier 42, M42, or NGC 1976, is a diffuse nebula located south of the Orion belt. It is one of the brightest nebulae that exist and is one of the few that can be observed with the naked eye on the night sky. It is located about 1,270 light years from Earth and has an approximate diameter of 24 light years.

The Orion Nebula shines in this VLT Survey Telescope image. ESO/G. Beccari

Now, Astronomers and visualization specialists from NASA’s Universe of Learning program have created a spectacular three-dimensional movie of the Orion Nebula, the cosmic stellar nursery.

With the aid of visible and infrared cameras of the Hubble and Spitzer space telescopes along with Hollywood techniques, a team from the Space Telescope Science Institute in Baltimore, Maryland, and the Caltech / IPAC in Pasadena, California, have produced the best and most detailed visualization of multiple wavelengths of the Orion nebula.

The Goal is to create a new generation of products and experiences developed by NASA’s Universe of Learning program, that enables not only scientists but the general public to explore fundamental questions in science, experience how science is done, and discover the universe for themselves.

“Being able to fly through the nebula’s tapestry in three dimensions gives people a much better sense of what the universe is really like,” explained the Space Telescope Science Institute’s visualization scientist Frank Summers, who led the team that developed the movie.

“By adding depth and structure to the amazing images, this fly-through helps elucidate the universe for the public, both educating and inspiring,” added Summers.

The three-minute movie allows viewers to glide through the picturesque star-forming region and experience the universe in a new and exciting way, according to NASA.

“Looking at the universe in infrared light gives striking context for the more familiar visible-light views. This movie provides a uniquely immersive chance to see how new features appear as we shift to wavelengths of light normally invisible to our eyes,” said Robert Hurt, lead visualization scientist at IPAC.

Here’s the video, ENJOY!

https://youtu.be/xCFg5udYbAg

Source: NASA Space Telescopes Provide a 3D Journey Through the Orion Nebula