During the mid - belated Eocene date of reference , 44 - 34 million years ago , large parts of Antarctica were ice - free , creating room for river systems now long frozen . Sediments from the Amundsen Sea come all the direction from the stack range that spans the continent , divulge there was no inland sea in between to capture them .
The world was a hotter berth in general 40 million yr ago , but the difference was most stark in Antarctica . nifty ocean current drew warm water down from the equator to lap at its margin , before the formation of theAntarctic Circumpolar Currentblocked their passage . Consequently , while the highland were glaciate , and the lowland got snowy in wintertime , forests flourish .
forest need rain , and regular pelting means rivers . However , identifying where these ran is challenging . There has been flock of time for the landscape to change since the frosting come up . Consequently , we ca n’t just face at the current lie of the land and assume water flowed to what is now the low distributor point .
For around 10 million years, a river flowed from the Transantarctic mountains to the Amundsen Sea. The route is not known, but the most likely one is outlined here.Image credit: Zundel et al., Science Advances 2024 (CC BY 4.0)
Drilling through all that ice to demonstrate what it was like long ago is a challenge , but Professor Cornelia Spiegel of the University of Bremen and fellow worker found an easier way of life to identify Antarctica ’s lose river . They practise into deposit around the sea-coast using the icebreakerPolarstern .
In the Amundsen Sea , the team found 17 - 24 meters ( 56 - 79 feet ) of deposit write of minerals that do not match those of nearby West Antarctica . rather , these came from the Transantarctic Mountains , which fraction East and West Antarctica . unluckily , no fossils were found in these deposit to indicate the ecosystem of the era ,
As their name suggests , these mountains run right across the continent , but that carrefour is at right angles to a line from the South Pole to the Amundsen Sea . For the mineral to have reached there in the Eocene , they must have been bear by a river 1,500 kilometre ( 932 miles ) long , or more if it meandered .
Such a distance is not exceptional – it would just make the top 100 in the world today , but it would have dominate West Antarctica , then , as now , much humble than its eastern counterpart .
The Transantarctic debris would have been deposited into a sloppy river delta , with the writer choosing the Rhine and the Rio Grande ( the US / Mexico one ) as modern counterparts .
Mountain reach will always produceglaciers , river , or both to channel the hastiness that falls on them away . However , a much shorter trip to the sea might have been wait . “ The existence of such a transcontinental river scheme shows that – unlike today – large parts of West Antarctica must have been locate above sea storey as all-embracing , flat coastal plains , ” Spiegel said in astatement .
ocean floor were higher then , with much less water pin down in ice , so these West Antarctic plains must have been a fair morsel higher than they are today . On the other hand , they could n’t have been too high-pitched , or they would have been covered in ice , even under the warm condition of the fourth dimension .
Spiegel and co - author close a lot of consequence , let in the depositing of sediments in the Amundsen Sea , break - related magmatism , seafloor diffuse , and the rise of the Transantarctic Mountains all started around the same time : 44 - 40 million years ago . This observe around 40 million years when the area had between comparatively tectonically quiet . The deposition may have been stopped 34 million years ago by the attack of permanent glaciation , or by the growth of a seaway closer to the mountains .
give the eroding or remission that has read position since , we ca n’t expect the counter of such a river when West Antarctica is sparkler - loose , something that may happendisturbingly soon . Nevertheless , theauthors argue that only by understanding what the globe was like back then can we see how it deepen to one with lasting sheet of ice at the poles .
The subject is published inScience Advances .
