Arctic current flowed under deep freeze of last ice age, study says
"The Arctic Ocean must have been flushed at approximately the same rate it is today regardless of how different things were at the surface," said study co-author Jerry McManus, a geochemist at Columbia University's Lamont-Doherty Earth Observatory.
Researchers reconstructed Arctic circulation through deep time by measuring radioactive trace elements buried in sediments on the Arctic seafloor. Uranium eroded from the continents and delivered to the ocean by rivers, decays into sister elements thorium and protactinium. Thorium and protactinium eventually attach to particles falling through the water and wind up in mud at the bottom. By comparing expected ratios of thorium and protactinium in those ocean sediments to observed amounts, the authors showed that protactinium was being swept out of the Arctic before it could settle to the ocean bottom. From the amount of missing protactinium, scientists can infer how quickly the overlying water must have been flushed at the time the sediments were accumulating.
"The water couldn't have been stagnant, because we see the export of protactinium," said the study's lead author, Sharon Hoffmann, a geochemist at Lamont-Doherty.
The upper part of the modern Arctic Ocean is flushed by North Atlantic currents while the Arctic's deep basins are flushed by salty currents formed during sea ice formation at the surface. "The study shows that both mechanisms must have been active from the height of glaciation until now," said Robert Newton, an oceanographer at Lamont-Doherty who was not involved in the research. "There must have been significant melt-back of sea ice each summer even at the height of the last ice age to have sea ice formation on the shelves each year. This will be a surprise to many Arctic researchers who believe deep water formation shuts down during glaciations."
The researchers analyzed sediment cores collected during the U.S.-Canada Arctic Ocean Section cruise in 1994, a major Arctic research expedition that involved several Lamont-Doherty scientists. In each location, the cores showed that protactinium has been lower than expected for at least the past 35,000 years. By sampling cores from a range of depths, including the bottom of the Arctic deep basins, the researchers show that even the deepest waters were being flushed out at about the same rate as in the modern Arctic.
The only deep exit from the Arctic is through Fram Strait, which divides Greenland and Norway's Svalbard islands. The deep waters of the modern Arctic flow into the North Atlantic via the Nordic seas, contributing up to 40 percent of the water that becomes North Atlantic Deep Water -- known as the "ocean's lungs" for delivering oxygen and salt to the rest of world's oceans.
One direction for future research is to find out where the missing Arctic protactinium of the past ended up. "It's somewhere," said McManus. "All the protactinium in the ocean is buried in ocean sediments. If it's not buried in one place, it's buried in another. Our evidence suggests it's leaving the Arctic but we think it's unlikely to get very far before being removed."
Welcome to SUV System Ltd!
SUV System Ltd is ISO 90012008 Certified electronics distributor with 10 years of experiences.
We have built up long term business relationship with about many companies which are stockers and authorized agents. we have a steady and reliable supply to meet customer's demands to the greatest extent .Confidently, we are able to lower your cost and support your business with our years of professional service.
SUV System Ltd is Electronic Components Distributor Supplies,Find Quality Electronic Components Supplies Products IC(Integrated Circuits),Connectors,Capacitor,Resistors,Diodes,Transistors,LED at Suvsystem.com. Sourcing Other Energy, Environment, Excess Inventory Products from Manufacturers and Suppliers at Suvsystem.com
Electronic Components distributor:http://www.suvsystem.com
Connectors Distributor:http://www.suvsystem.com/l/Connectors-1.html
IC Distributor:http://www.suvsystem.com/l/IC(Integrated-Circuits)-1.html
LED Distributor:http://www.suvsystem.com/l/LED-1.html
Capacitor Distributor:http://www.suvsystem.com/l/Capacitor-1.html
Transistor Distributor:http://www.suvsystem.com/l/Transistors-1.html
Resistor Distributor:http://www.suvsystem.com/l/Resistors-1.html
Diode Distributor:http://www.suvsystem.com/l/Diodes-1.html
SUV System Ltd insists on the managing faith ofsincereness,speciality,foresight, win-win,so we build up stable-relationship customers located all over the world, including the States, Europe, Argentina, UAE, Malaysia, Australia,and India etc
we are focus on the following fields,and hope we can help you.
CRCW080520R0JNEA CRCW080520R0FKTA CRCW080520R0FKEB CRCW080520R0FKEAHP CRCW080520R0FKEA CRCW080520K5FKTA CRCW080520K5FKEA CRCW080520K0JNTA CRCW080520K0JNEB CRCW080520K0JNEA CRCW080520K0FKTC CRCW080520K0FKTA CRCW080520K0FKEB CRCW080520K0FKEAHP CRCW080520K0FKEA CRCW0805205RFKTA CRCW0805205RFKEA CRCW0805205KFKTA CRCW0805205KFKEA CRCW0805200RKNEAIF CRCW0805200RJNTA CRCW0805200RJNEB CRCW0805200RJNEA CRCW0805200RFKTA CRCW0805200RFKEB CRCW0805200RFKEA CRCW080522K1FKEB CRCW080522K1FKEA CRCW080522K0JNTA CRCW080522K0JNEB CRCW080522K0JNEAIF CRCW080522K0JNEAHP CRCW080522K0JNEA CRCW080522K0FKTA CRCW080522K0FKEB CRCW080522K0FKEA CRCW0805226RFKTA CRCW0805226RFKEA CRCW0805226KFKTA CRCW0805226KFKEA
http://www.suvsystem.com/a/1923.aspx
