Over the years, Josh Willis, a scientist with NASA’s Jet Propulsion Laboratory, and his Oceans Melting Greenland (OMG) team have flown out of Kulusuk, Greenland to study the waters that surround one of the world’s biggest islands.
They have worked tirelessly to understand the role that the sea plays in the melting of Greenland’s glaciers.
On their current visit this month, Greenland experienced record warm temperatures with a few locations reaching over 70 degrees Fahrenheit during the last week of July into the first week of August; the same heatwave that smashed high-temperature records in Europe in late July.
On average, the Greenland ice sheet is now losing about 281 billion tons of ice per year.
This loss of ice has resulted in nearly 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. However, on August 2, Greenland lost 12.5 billion tons of ice to melt, the most massive single-day loss in recorded history.
Greenland’s record for ice loss, set in 2012, could be broken in 2019.
Nevertheless, it’s not just the warmer than typical air temperatures that are resulting in Greenland ice sheet melt; it’s mostly the warming oceans.
To better understand this process, the OMG team has deployed numerous bathythermograph (BT) buoys from a recently refurbished Douglas DC-3 cargo plane, which served in the Normandy Invasion in 1944, 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.
Throughout the world’s oceans, you usually have a negative thermocline. In other words, as you fall deeper and deeper into the sea, the water becomes colder, until you reach a region referred to as cold deep-water thousands of feet down. That’s 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.
On a recent fight in the DC-3, while observing BT buoy ocean temperature data, OMG team member Ian Fenty noted, “It’s very rare anywhere on the planet to see 700 meters of no temperature variation, but right in front of the glacier it’s warm all the way up. These warm waters now are able to be in direct contact with the ice over its entire face, supercharging the melting.”
During the summer months, copious amounts of freshwater melt from the glaciers of Greenland into the sea. This freshwater is less dense and floats to the surface while the salty and warmer Atlantic water lurks below.
“OMG is observing the water temperatures on the continental shelf around Greenland to see how it changes,” Willis told me. “At the same time, we are observing the glaciers and how they react to the warm, salty Atlantic water. In the long run, this Atlantic water will control just how fast the ice disappears.”
Willis is one of the most dedicated and knowledgeable climate scientists I have ever met. He also worked on the satellites programs that have been measuring the sea level.
Years ago, NASA launched two satellites from Vandenberg Air Force Base — Jason 1 in 2001 and Jason 2 in 2008. In 2016, they launched Jason 3.
These satellites measure sea levels over most of Earth using an extremely precise radar altimeter. The altimeter transmits radio waves from the satellite to the ocean’s surface and measures the time it takes for the radio waves to bounce back. This technique has proved to be particularly precise and accurate. In fact, Jason 3 has a goal to measure sea-level variations of 1 inch, or 2.5 centimeters.
“These satellites give us a global view of our changing oceans with such exquisite accuracy that even the yearly rise and fall of global sea level is visible, caused by the transfer of water to and from the continents in the form of rain and river runoff,” said Willis, who has been an authority on sea level changes for many years.
Sea level change is the best way to measure global warming. 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.
Willis told me thatabout 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.
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.
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