Mauna Kea reveals long-distance effect of the North Atlantic Current

Deterioration of the circulation caused climate change on the other side of the world

Mauna Kea © Oregon State University
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At the summit of Mauna Kea in Hawaii, geo-researchers have come up with surprising evidence of a global climate impact of the North Atlantic Current thousands of miles away. Its weakening some 15, 000 years ago triggered a climate change in Hawaii, which allowed the summit glacier of the volcanic mountain to grow again. This finding, now published in the journal "Earth and Planetary Science Letters, " is particularly important because climatologists expect a further weakening of the North Atlantic Current in the course of climate change.

Hawaii's Mauna Kea is the highest mountain in the world when measured from its base deep down on the ocean floor. The volcano, which has been resting for thousands of years, today has a subtropical mild climate, but during the last ice age, some 21, 000 years ago, it carried a summit glacier. When the ice age ended, this ice cap shrank - so far, so well known. But now American researchers have found evidence that the summit glacier thereafter, about 15, 400 years ago, grew again. You already have a pretty good idea why.

Icecap once again grown after the ice age

"Until 14, 500 years ago, Mauna Kea owned a large ice cap of approximately 70 square kilometers, which has now completely disappeared, " said Peter Clark, professor of Earth Sciences at Oregon State University and head of the study, which involved scientists from several American research institutions. "We have now gained new data that tell us when, where and most likely why the glaciers existed and disappeared again."

The data for their study provided boulders from the summit of the volcanic mountain that thousands of years ago had been dragged off the glacier. Using measurements of a helium isotope in the rock, the researchers were able to determine when the chunks were then freed from their ice cover and exposed to the atmosphere. The development of the summit glacier was comprehensible in detail.

Time correlation with weakening of the North Atlantic Current

The evaluation showed that the renewed, short-term growth of the glacier some 15, 400 years ago coincided perfectly with a dramatic event almost at the other end of the earth, in the North Atlantic. For just about this time, the North Atlantic Current, also known as the "Atlantic Meridional Circulation Flow", weakened sharply. The flow ensures that warm water is transported from the tropics to the north, where it then cools and sinks. The cold deep water from polar latitudes is brought back to warmer climes. display

Among other things, this "circulation pump" ensures that Europe has a comparatively mild climate and generally plays an important role in the global climate system. It is already known that the North Atlantic flow has weakened several times in the course of recent geological history, and in some cases even came to a complete standstill. Climate researchers also fear that such an event, triggered by increased meltwater inflow in the Arctic seas, could be repeated in the context of climate change.

Climate change thousands of kilometers away

How big the consequences would be if the flow actually becomes weaker or even collapses completely, it is still unclear. However, the events now observed in Hawaii suggest that the consequences could be global. The new data from Mauna Kea, together with the results of data found in seascapes and lakes in other regions, show that the waning of the North Atlantic current climate changes everywhere in the world, "says Clark.

The events in the North Atlantic at the time made it clear that the climate in Hawaii was getting colder as well as significantly wetter. The precipitation rate was three times higher than today, the researchers said. The island could also have been hit more often by violent storms from the north. These connections are quite remarkable: a current in the North Atlantic influences glacier development thousands of miles away on the islands of Hawaii, says Clark. "The global impact of flow changes was just massive."

If the North Atlantic Current, as fu- tured by climate researchers, actually becomes weaker in a few decades, this could lead to worldwide consequences.

(Oregon State University, 09.08.2010 - NPO)