Newly discovered Icelandic current could change climate picture

Terra Daily: If you'd like to cool off fast in hot summer weather, take a dip in a newly discovered ocean current called the North Icelandic Jet (NIJ). You'd need to be far, far below the sea's surface near Iceland, however, to reach it. Scientists have confirmed the presence of the NIJ, a deep-ocean circulation system off Iceland. It could significantly influence the ocean's response to climate change.



The NIJ contributes to a key component of the Atlantic Meridional Overturning Circulation (AMOC), critically important for regulating Earth's climate. As part of the planet's reciprocal relationship between ocean circulation and climate, the AMOC transports warm surface water to high latitudes where the water warms the air, then cools, sinks and returns toward the equator as a deep flow.



Crucial to this warm-to-cold oceanographic choreography is the Denmark Strait Overflow Water (DSOW), the largest of the deep, overflow plumes that feed the lower limb of the AMOC and return the dense water south through gaps in the Greenland-Scotland Ridge.



For years it has been thought that the primary source of the Denmark Overflow was a current adjacent to Greenland known as the East Greenland Current. However, this view was recently called into question by two oceanographers from Iceland who discovered a deep current flowing southward along the continental slope of Iceland. They named the current the North Icelandic Jet and hypothesized that it formed a significant part of the overflow water....



Northern part of Denmark Strait showing the location of the newly discovered deep current in relation to the known existing pathway of dense water. (Graphic by Jack Cook, Woods Hole Oceanographic Institution)

Thawing permafrost could release vast amounts of carbon and accelerate climate change by the end of this century

Dan Krotz in the Lawrence Berkeley National Labotatory News: Billions of tons of carbon trapped in high-latitude permafrost may be released into the atmosphere by the end of this century as the Earth’s climate changes, further accelerating global warming, a new computer modeling study indicates. The study also found that soil in high-latitude regions could shift from being a sink to a source of carbon dioxide by the end of the 21st century as the soil warms in response to climate change.



The research was led by Charles Koven of the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab). He conducted the research with a team of scientists from France, Canada, and the United Kingdom while he was a postdoctoral researcher at France’s Laboratoire des Sciences du Climat et de l’Environnement. The modeling was conducted at a supercomputing facility run by France’s Alternative Energies and Atomic Energy Commission.



...Their findings counter results from a comparison of models that was included in the Intergovernmental Panel on Climate Change’s 2007 fourth assessment report. The comparison found that climate change will spark a growth in high-latitude vegetation, which will pull in more carbon from the atmosphere than thawing permafrost will release.



But unlike earlier models, the new model includes detailed processes of how carbon accumulates in high-latitude soil over millennia, and how it’s released as permafrost thaws. Because it includes these processes, the model begins with much more carbon in the soil than previous models. It also better represents the carbon’s vulnerability to decomposition as the soil warms.



As a result, the new model found that the increase in carbon uptake by more vegetation will be overshadowed by a much larger amount of carbon released into the atmosphere. “Including permafrost processes turns out to be very important,” says Koven, who joined Berkeley Lab’s Earth Sciences Division as a staff scientist earlier this year. “Previous models tended to dramatically underestimate the amount of soil carbon at high latitudes because they lacked the processes of how carbon builds up in soil. Our model starts off with more carbon in the soil, so there is much more to lose with global warming.”...



A sink becomes a source, as revealed by these two simulations of net CO2 fluxes due to climate change at the end of 21st century. The control simulation on the left did not include permafrost processes. The permafrost simulation on the right included processes that depict how carbon accumulates in soil and how it decomposes. In the latter simulation, large carbon losses are seen in central Canada where substantial permafrost stocks exist that are vulnerable to warming. Units are in grams of carbon per square meter per year.