Weather Watch

Where the ocean is ‘upside down’ is essential for showing us how fast it’s rising

Over the course of my naval career, I’ve helped deploy hundreds of bathythermobuoy (BT) buoys from aircraft like the H-2 Seasprite and H-3 Sea King helicopters and P-3 Orion fixed-wing aircraft.

These buoys are shot from these aircraft in canisters and deploy a small parachute as they descend toward the ocean. At water impact, a float instantaneously inflates with a radio transmitter, while at the same time, a temperature probe descends through the water column and produces a continuous reading of temperature versus depth chart.

Throughout the world’s oceans, you usually have a negative thermocline, in other words, as you fall deeper and deeper into the sea the colder the water becomes, until you reach a region referred to as cold deep-water thousands of feet down where the water becomes isothermal, with no temperature change all the way to the ocean’s floor.

However, in the Arctic and Antarctic regions, the reverse is true, as you descend, the water warms up. It’s where the ocean is upside down and here is why this seawater temperature anomaly is so essential.

During the summer months, copious amounts of freshwater melt from the glaciers of Greenland into the sea. This fresh water is less dense and floats to the surface while the salty and warmer Atlantic Water lurks below.

Jet Propulsion Laboratory (JPL) scientist Josh Willis and the NASA Oceans Melting Greenland (OMG) team have worked tirelessly to understand the role that ocean water plays in the melting of Greenland’s glaciers.

To better understand this process, the OMG team has deployed numerous (BT) buoys from a recently refurbished Douglas DC-3 cargo plane, which served in the Normandy Invasion in1944, around Greenland’s glaciers. But there’s a twist; the buoys also measure salinity. The OMG team discovered that many of these glaciers extend 3,000 feet into the sea where the warmer Atlantic Ocean water is present and in turn melts the ancient ice from below.

“Over a five-year period, OMG is observing the water temperatures on the continental shelf around Greenland to see how it changes,” Dr. Willis told me. “At the same time, we are observing the glaciers and how they react to the warm, salty Atlantic water. The sea floor plays a big part, too, because the complicated network of canyons steer that warm water and determine whether or not it can reach the glaciers. In the long run, this Atlantic Water will control just how fast the ice disappears.”

You see, the oceans have absorbed about 95 percent of the increased heat due to human-made (anthropogenic) climate change since the Industrial Revolution with the top 2,300 feet of ocean showing warming of more than 0.4 degrees Fahrenheit.

On average, the Greenland ice sheet is now losing about 281 billion tons of ice per year. This loss of ice has resulted in about a half an inch of sea-level increase throughout the world. If all the ice were to melt from Greenland, it would produce about a 25-foot rise in sea level.

Dr. Willis is one of the most dedicated and knowledgeable climate scientists I have ever met. He told me that so far about 40 percent of the recent sea-level increase is due to thermal expansion of the ocean, 30 percent from land glaciers and 30 percent from the melting of the ice sheets in Greenland and Antarctica.

In the future, not only will the rate of sea-level rise increase, but the main contributor will be the melting of the ice sheets. Tragically, most of the land glaciers will be gone. In fact, by 2100 most climate scientist are expecting about a 47-inch increase in sea level.

Dr. Bill Patzert, a respected oceanographer and meteorologist who worked for JPL for nearly four decades, told me that the climate models have continuously underestimated sea-level increase and air-temperature rise.

This is not reassuring since more than 600 million people throughout the world live in coastal areas that are less than 33 feet above sea level and will have to migrate to higher ground.

John Lindsey’s column is special to The Tribune. He is PG&E’s Diablo Canyon marine meteorologist and a media relations representative. Email him at or follow him on Twitter: @PGE_John.
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