My Turn: Will melting Greenland ice divert Gulf Stream?

Rob Moir in Tasiilaq, Greenland.

Rob Moir in Tasiilaq, Greenland. CONTRIBUTED

By ROB MOIR

Published: 02-07-2024 7:08 PM

With climate change, a 1% increase in watts per square meter of heat energy is warming the ocean, causing seawater to swell, currents to flow stronger, and greater storms to rage. Ancient Greeks believed Oceanus, the ocean river, separated the known world from the unknown where sea monsters like the Kraken dwell. The ocean remains the mysterious wine-dark sea where we voyage out on the surface or survey from distant satellites, unable to see what lurks in the darkening depths below.

A New York Times article evoked our ancestral fears: “The warming atmosphere is causing an arm of the powerful Gulf Stream to weaken. … The northern arm of the Gulf Stream is but one tentacle of a larger, ocean-spanning tangle of currents called the Atlantic Meridional Overturning Circulation.”

Some scientists fear that meltwater from Greenland is already inhibiting the northward flow of the Gulf Stream. They believe freshwater pooling over the briny sea will slow the current. They say one of the hallmarks of a shutting down of ocean currents is a cold blob of water they’ve identified beyond Newfoundland in the Northwest Atlantic Ocean.

“In short, the cold blob may signal that the northern arm of the Gulf Stream no longer arrives with the same strength to the North Atlantic,” said Peter de Menocal, president of the Woods Hole Oceanographic Institution.

The end is nigh, according to their readings of Greenland ice cores and foraminifera sands. During the last ice age, around 22,000 years ago, ocean circulation stopped and started. “The climate system is an angry beast, and we are poking it with sticks,” de Menocal says. If we do not change our ways, the great switch will be flipped; the threshold will be crossed, and rapid, cascading effects will follow to all corners of the globe.

Should we fear that the melting Greenland ice will tip the delicate balance of hot and cold that defines not only the North Atlantic but also “life far and wide?”

Let’s walk back the cat on Kraken-rattling and look at how more buoyant fresh water could impede the motion of saltier water, how meltwater from Greenland inhibits ocean currents, and why the cold blob in the North Atlantic (not be confused with a posse of cold-core eddies in the Sargassum Sea) threatens to upset the global balance.

Fresh water is less dense than salty water. Off the coast of Brazil, fresh Amazon River water tongues out 30 miles over the Atlantic South Equatorial Current. Racing dinghy sailors look for a slippery sea, a patch of freshwater that may move differently than the tidal current. Scientists have changed their explanation from meltwater slowing currents to acting as an insulating blanket impeding the sinking “into the deep ocean, and that could ultimately disrupt the transport of heat to the north.

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Greenland has an awesome amount of meltwater. One summer, the volume of meltwater could have covered all of California four feet deep. Because Greenland is more than five times the size of California, the water was 8-10 inches on top of the ice.

The surface of Greenland’s ice sheet looks corrugated with rows of ice interlaced by water. The meltwater, pooled on the ice surface, is measured from satellites. When it freezes in October, it cannot be determined if more or less than 50% of the meltwater froze. With warmer summers, plants take up more water to photosynthesize carbon out of the atmosphere. No significant increase in meltwater reaching the ocean has been observed in Greenland.

The cold blob is part of the Labrador Current barreling south with nutrient-rich water from the Arctic Ocean, where more sea ice forms in October, sinking more salty icy water. Cold water carries more oxygen. It is upwelled onto the Grand Banks, where the best fishing grounds in the Atlantic Ocean are found.

Fears unfounded, melting Greenland ice will not tip the delicate balance of hot and cold that defines the North Atlantic. There is no switch we can throw quickly or an angry beast to poke.

Like a pickpocket’s jostle and sleight of hand, our attention is diverted, and we don’t know what we’ve lost until it’s gone. People were not deceived when large swaths of forests were cut down following the Civil War. George Perkins Marsh explained how the clear-cutting of forests would lead to desertification. Look what agriculture did to the once-lush lands of the Sahara. “The operation of causes set in action by man has brought the face of the earth to a desolation almost as complete as that of the moon,” he wrote.

Marsh argued when vegetation and soils are removed, there will be insufficient groundwater to provide the Erie Canal with adequate depth for barges to operate, and New York’s burgeoning economy would suffer. The solution was to create the Adirondack State Park for watershed protection, to the chagrin of land barons.

Let’s not be fooled again. One hundred billion tons of excess carbon dioxide in the atmosphere is said to cause climate change. A global increase in soils and vegetation of 2% would restore the atmosphere to 350 parts per million carbon.

Rob Moir is a nationally recognized and award-winning environmentalist. He is president and executive director of Cambridge-based Ocean River Institute, a nonprofit providing expertise, services, resources, and information unavailable on a localized level to support the efforts of environmental organizations. Please visit www.oceanriver.org for more information.