by 
Naturlig nedkjøling fikk isbreene til å vokse
Det naturlige klimasystemet har mekanismer som kan utløse brå klimaendringer. Ny forskning antyder at spontan nedkjøling kan ha fått arktiske isbreer til å vokse lenge før den lille istiden, uten påvirkning utenfra.
For noen hundre år siden rykket breene frem i hele Europa, mens klimaet ble kaldere. Dette er den såkalte lille istid, og skylden legges vanligvis på vulkanutbrudd og et minimum i stråling fra solen i det 13. århundre.
Denne teorien er imidlertid vanskelig å få til å stemme med nyere data som viser at arktiske breer begynte å vokse mye tidligere. En ny studie fra Bjerknessenteret for klimaforskning antyder at denne overraskende regionale effekten kan ha blitt utløst av spontane klimaendringer.
Arktiske breer begynte å vokse flere hundre år før andre breer i Europa
– Jeg har studert de prehistoriske endringene i breene i Arktis i noen år nå og lurt på hvorfor den lille istiden der har ligget flere hundreår foran endringene ellers i Europa, sier artikkelens hovedforfatter, geologen Willem van der Bilt.
Vulkanutbrudd og endringer i solinnstråling er viktige triggere i naturlig klimaendring. I denne perioden var det ingen store variasjoner, og dermed er det ikke innlysende hvorfor det skulle inntreffe store endringer i klimaet. På grunn av det antatt stabile klimaet har tidsintervallet mellom år 700 og år 1000 blit kalt for middelalderens stille periode.
– Å sammenstille mer og mer data som viste den samme trenden brakte meg ikke nærmere noen forklaring, sier van der Bilt.
– Heldigvis tvang noen av kollegene mine meg ut av komfortsonen ved å snakke med modellører om å forklare mønstrene i disse dataene.
Resultatet er en ny studie, som nylig er publisert i tidsskriftet Quaternary Science Reviews, der forfatterne utfordrer ideen om at klimavariasjoner alltid krever påvirkning utenfra.
Kombinerte modeller og empiriske tilnærminger
– Klimamodeller har simulert brå endringer som utvikler seg spontant, sier en av forskerne bak artikkelen, fysikeren Andreas Born.
– Men ofte har disse eksperimentene blitt sett på som klimamodelleringens stygge andunger.
Det er ikke tilfellet denne gangen. Ved å sammenligne geologiske bevis med modellberegninger, ble Born og van der Bilt overbevist om at den tidlige fremveksten av de arktiske breene under den lille istiden kunne forklares med spontan avkjøling.
– Det vi mener, er at disse endringene ikke krevde eksterne mekanismer, men oppsto tilfeldig, forklarer van der Bilt.
– I dette tilfellet var det endringer i atmosfæren øst for Grønland som satte i gang rask vekst av sjøis, legger Born til.
Sjøisen spiller en viktig rolle i å kjøle ned det arktiske klimaet ved å reflektere solstråling og hindre havet i å tape varme til atmosfæren. Slik kan vekst av sjøis ha ledet til kaldere forhold, som igjen kan ha intensivert veksten av is. Denne kjeden av selvforsterkende hendelser, kjent som en tilbakekoblingsløkke, medførte en endring fra unormale værforhold i et lite område til en fase med vekst av breer og sjøis i og rundt hele Nord-Atlanteren.
– Ting eskalerte brått. Innen noen tiår hadde avkjølingen bredt seg hele veien fra Grønland til Svalbard, sier van der Bilt.
Dette karakteristiske endringsmønsteret fanges opp av geologiske data så vel som modellresultater, demonstrert gjennom en statistisk analyse utført av en av de andre artikkelforfatterne, ph.d-kandidaten Kristian Haaga.
Van der Bilt og Born argumenterer for at arbeidet deres understreker hvorfor klimaforskere bør kombinere modellering og empiriske tilnærminger.
– Modellberegninger representerer mulige scenarioer for klimaendring. Å sammenligne disse med geologiske data kan fortelle oss i hvor stor grad de representerer virkeligheten, sier Born.
– Og motsatt, ved å definere nøkkelkomponenter i klimasystemet hjelper modellene oss med å forstå dataene våre, tilføyer van der Bilt.
– Og det er nettopp det som skjedde med denne artikkelen. Vi demonstrerer at simuleringer av spontane endringer ikke er så hypotetiske som tidligere antatt, mens vi tilfører en forklaring på en gåtefull fase med betydelige klimaendringer.
Referanse
van der Bilt, Willem GM, Born, Andreas & Haaga, Kristian A (2019) Was Common Era glacier expansion in the Arctic Atlantic region triggered by unforced atmospheric cooling? Quaternary Science Reviews, 222, p. 105860.
글 너무 잘 쓰시네요. 추천!
Really useful post with tips I can actually use. Keep it coming!
I have read some good stuff here. Certainly worth bookmarking for revisiting. I wonder how much effort you put to create such a magnificent informative site.
I like this website very much so much wonderful info .
I consider something really interesting about your weblog so I saved to fav.
This was not only informative but also inspiring. Thanks for sharing!
Great work! This is the type of information that should be shared around the internet. Shame on Google for not positioning this post higher! Come on over and visit my website . Thanks =)
Thanks , I have just been looking for info approximately this subject for a while and yours is the greatest I have discovered so far. However, what about the conclusion? Are you certain in regards to the supply?
I just couldn’t depart your web site prior to suggesting that I really enjoyed the standard information a person provide for your visitors? Is going to be back often to check up on new posts
Great wordpress blog here.. It’s hard to find quality writing like yours these days. I really appreciate people like you! take care
I like what you guys are up too. Such smart work and reporting! Carry on the superb works guys I have incorporated you guys to my blogroll. I think it will improve the value of my website 🙂
I learned a lot from this.
Hello. fantastic job. I did not anticipate this. This is a remarkable story. Thanks!
Pretty nice post. I simply stumbled upon your blog and wished to mention that I have really loved surfing around your weblog posts. After all I will be subscribing on your feed and I am hoping you write again very soon!
F*ckin’ amazing issues here. I am very glad to look your article. Thanks a lot and i am looking ahead to contact you. Will you please drop me a mail?
Rattling wonderful information can be found on blog.
I like this post, enjoyed this one thanks for putting up.
I absolutely love your blog and find a lot of your post’s to be just what I’m looking for. can you offer guest writers to write content to suit your needs? I wouldn’t mind composing a post or elaborating on a lot of the subjects you write regarding here. Again, awesome website!
As soon as I discovered this website I went on reddit to share some of the love with them.
It’s actually a great and helpful piece of info. I’m satisfied that you just shared this useful info with us. Please keep us up to date like this. Thank you for sharing.
The very crux of your writing while appearing agreeable originally, did not really settle properly with me after some time. Someplace throughout the sentences you actually were able to make me a believer but just for a while. I nevertheless have a problem with your jumps in logic and you would do nicely to help fill in all those breaks. When you actually can accomplish that, I would certainly end up being amazed.
Good day! This is kind of off topic but I need some help from an established blog. Is it very difficult to set up your own blog? I’m not very techincal but I can figure things out pretty fast. I’m thinking about setting up my own but I’m not sure where to begin. Do you have any tips or suggestions? Cheers
I got what you intend, thankyou for putting up.Woh I am delighted to find this website through google.
Today, I went to the beach with my children. I found a sea shell and gave it to my 4 year old daughter and said “You can hear the ocean if you put this to your ear.” She placed the shell to her ear and screamed. There was a hermit crab inside and it pinched her ear. She never wants to go back! LoL I know this is totally off topic but I had to tell someone!
Very interesting points you have mentioned, regards for putting up. “What is harder than rock, or softer than water Yet soft water hollows out hard rock. Persevere.” by Ovid.
I couldn’t resist commenting
he blog was how do i say it… relevant, finally something that helped me. Thanks
Respect to op, some excellent entropy.
I truly enjoy looking through on this website , it has excellent articles. “Sometime they’ll give a war and nobody will come.” by Carl Sandburg.
It¦s really a cool and helpful piece of info. I¦m happy that you simply shared this useful info with us. Please stay us informed like this. Thank you for sharing.
I love your blog.. very nice colors & theme. Did you make this website yourself or did you hire someone to do it for you? Plz reply as I’m looking to construct my own blog and would like to know where u got this from. cheers
I’ve been exploring for a bit for any high-quality articles or blog posts in this kind of house . Exploring in Yahoo I finally stumbled upon this website. Reading this information So i am glad to convey that I’ve an incredibly good uncanny feeling I found out just what I needed. I most indisputably will make sure to do not put out of your mind this website and give it a look on a relentless basis.
Thanks for sharing. I read many of your blog posts, cool, your blog is very good.
WONDERFUL Post.thanks for share..more wait .. …
Greetings from California! I’m bored to death at work so I decided to browse your website on my iphone during lunch break. I love the knowledge you present here and can’t wait to take a look when I get home. I’m shocked at how quick your blog loaded on my mobile .. I’m not even using WIFI, just 3G .. Anyhow, very good site!
I like this post, enjoyed this one regards for putting up.
I don’t think the title of your article matches the content lol. Just kidding, mainly because I had some doubts after reading the article.
It’s actually a cool and helpful piece of info. I am glad that you shared this useful information with us. Please stay us informed like this. Thank you for sharing.
I like what you guys are up also. Such clever work and reporting! Keep up the superb works guys I have incorporated you guys to my blogroll. I think it will improve the value of my site 🙂
Find real call girl in Lucknow and independent escort service in India. View photos, and genuine phone numbers. Simple, direct and private connections in Lucknow. Explore the best local profiles today.
This article is very helpful to me.