The Arctic Ocean has an important role in Earth’s climate. The Arctic is part of the globe that is most sensitive to climate change. The choke point for the Arctic Ocean is the Fram Strait. Currently the Arctic is shifting to a new normal; sea-ice is thinning, permafrost is thawing, and tundra is greening .
|Arctic sea ice minimum 2012 compared to 30 average minimum [a]|
Freezing and cooling produce deep water in the Arctic ocean. Only if it is exported at depth out of the Arctic Ocean, then it is contributing to the global thermohaline circulation. The thermohaline circulation of the oceans is the slow vertical overturning of its water that brings heat and oxygen into the depth of the world ocean. One of the drivers of this circulation is the deep, cold and salty water that is flowing through the Fram Strait out in depth from the Arctic Ocean. To understand climate change processes it has to be assessed how the outflow of deep water from the Arctic Ocean varied during last several ten-thousand years.
|Flow through Fram Strait - top/in & bottom/out [b]|
These radioactive tracers are produced in sea water by radioactive decay of natural uranium, which is transported by the rivers into the sea. Thorium and protactinium are not soluble in seawater and attach in a different time-depending manner to particles made of different minerals. These particles drop to the sea bottom and so remove the radioactive traces from the water column. This process is called “scavenging”. The “scavenging” of thorium and protactinium happens with a different speed. Much of the thorium will drop to the bottom even if much deep water is flowing out of the Arctic ocean. However an important part of the protactinium would be swept out through the Fram Strait if the outflow of Arctic waters is happening. Thus, the thorium and protactinium concentrations in sediments of the Arctic Ocean vary with the strength of the outflow of deep water through the Fram Strait. Whether that outflow varied during glacial, de-glacial and interglacial conditions can be studied in sediment cores taken from the bottom of the Arctic Ocean.
 Sharon S. Hoffmann, Jerry F. McManus, William B. Curry & L. Susan Brown-Leger, 2013, Persistent export of 231Pa from the deep central Arctic Ocean over the past 35,000 years
Nature 497, 603–606, http://www.nature.com/nature/journal/v497/n7451/full/nature12145.html
[b] from: http://www.arcticsystem.no/en/outsideworld/oceancurrents/
[c] from: http://www.larrymylesreports.com/thorium.htm