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How Climate Change Could Jam The World’s Ocean Circulation

September 10, 2016

How Climate Change Could Jam The World’s Ocean Circulation

Scientists are closely monitoring a key current in the North Atlantic to see if rising sea temperatures and increased freshwater from melting ice are altering the “ocean conveyor belt” — a vast oceanic stream that plays a major role in the global climate system.

Mariusz Kluzniak/Flickr
Melting ice flows into the northern Atlantic Ocean in eastern Greenland.
Susan Lozier is having a busy year. From May to September, her oceanographic team is making five research cruises across the North Atlantic, hauling up dozens of moored instruments that track currents far beneath the surface. The data they retrieve will be the first complete set documenting how North Atlantic waters are shifting — and should help solve the mystery of whether there is a long-term slowdown in ocean circulation. “We have a lot of people very interested in the data,” says Lozier, a physical oceanographer at Duke University.

A similar string of moorings across the middle of the Atlantic, delving as deep as 3.7 miles from the Canary Islands to the Bahamas, has already detected a disturbing drop in this ocean’s massive circulation pattern. Since those moorings were installed in 2004, they have seen the Atlantic current wobble and weaken by as much as 30 percent, turning down the dial on a dramatic heat pump that transports warmth toward northern Europe. Turn that dial down too much and Europe will go into a deep chill.

Researchers have been worried about an Atlantic slowdown for years. The Atlantic serves as the engine for the planet’s conveyor belt of ocean currents: The massive amount of cooler water that sinks in the North Atlantic stirs up that entire ocean and drives currents in the Southern and Pacific oceans, too. “It is the key component” in global circulation, says Ellen Martin, a paleoclimate and ocean current researcher at the University of Florida.

…click on the above link to read the rest of the article…

Bond Cycles and the Role of The Sun in Shaping Climate

April 11, 2016

Bond Cycles and the Role of The Sun in Shaping Climate

Bond cycles are defined by petrological tracers from core samples in the N Atlantic that link to the pattern of drift ice distribution. They provide a record of shifting ocean currents and winds, in particular periodic weakening of the North Atlantic current and strengthening of the Labrador current. These cycles shape what we perceive as climate change in the circum North Atlantic realm, for example the Little Ice Age and Medieval Warm Period. They leave a small mark on global average temperatures that are difficult to resolve in the proxy temperature records

Bond Cycles correlate with cosmogenic 10Be suggesting that variations in solar and terrestrial magnetic field strength somehow link to changes in atmospheric circulation and ocean currents. My favoured explanation is changes in solar spectrum that accompany changes in the magnetic field.

With tens of thousands of papers published in climate science, it is possible to pick any 50 and come up with almost whatever narrative one wants. In this post I focus on evidence from ice rafted debris (IRD) dispersed in the N Atlantic from drift ice as presented by Bond et al 2001 [1]. I like the data because it is coherent with what is known about historic climate change in the N Atlantic realm (Figure 3).

Bond Data

Glaciers entrain rocks and rock fragments from the bedrock across which they grind and when they enter the sea to become icebergs and begin to slowly melt this detritus rains down to the sea bed (see inset photo up top). This ice rafted debris (IRD) can tell us something about where the icebergs came from. If the fragments are of granite or schist then this does not tell us anything specific about the source since granite and schist is common in many bedrock areas. But if the fragments are of volcanic glass, then they can only come from Iceland in the North Atlantic realm.

…click on the above link to read the rest of the article…

The Oceans Are Becoming Too Hot for Coral, and Sooner than We Expected

October 10, 2015

The Oceans Are Becoming Too Hot for Coral, and Sooner than We Expected

Soon the oceans will be too warm to support thriving coral reefs. USFWS – Pacific Region/Flickr, CC BY

This week, scientists registered their concern that super-warm conditions are building to a point where corals are severely threatened across the tropical Indian, Pacific and Atlantic oceans. They did so after seeing corals lose colour across the three major ocean basins – a sign of a truly momentous global change.

This is only the third global bleaching event in recorded history.

Underwater heat waves

The situation has been worrying scientists like myself for many months. Over the past 12 months, the temperatures of the upper layers of the ocean have been running unseasonably warm. Underwater heatwaves have torn through these tropical regions over summer, and corals across large areas of reef have lost their colour as the algal partners (or symbionts) that provide much of the food for corals have left their tissues. Bereft, corals are beginning to starve, get diseased and die.

The “heatwaves” that are causing the problem are characterised by extremes that are 1-3 degrees C warmer than the long-term average for summer. It doesn’t seem like much but past experience has shown us that exposure to small increases in temperatures for a couple of months is enough to kill corals in great numbers.

In the first global mass bleaching event in 1998, regions such as Okinawa, Palau and north-west Australia lost up to 90% of their corals as temperatures soared.

By the end of 1998 up to 16% of the corals on the world’s tropical reefs had died.

The key concern here is that corals are not an inconsequential part of the biology of the ocean. While geographically insignificant (less than 0.1% of the ocean), coral reefs punch well above their weight in terms of their importance to the ecology of the ocean and to humans.

…click on the above link to read the rest of the article…

Olduvai IV: Courage
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Olduvai II: Exodus
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