by CAROL RASMUSSEN
NASA’s Ocean Melting Greenland, or OMG, campaign is back in the Arctic, and this month it’s dropping scientific probes out of a NASA aircraft into the water just off Greenland’s coastline. The probes are the fourth and final part of OMG’s observations this year documenting how seawater is melting the underside of the world’s second largest ice sheet.
Three things about Greenland: it’s huge, it’s remote, and it’s melting so fast that scientists use words like “falling apart” and “vanishing” to describe what they’re seeing. But the hugeness and remoteness mean that many parts of the island have gone completely unmeasured. There aren’t enough data for scientists to be confident that they understand how processes are interacting now, much less how the melting will progress in coming years.
“It’s hard to predict what’s going to happen to Greenland because we’ve never watched it melt before,” said Josh Willis, OMG’s principal investigator with NASA’s Jet Propulsion Laboratory, Pasadena, California. The measurements OMG is making this month, and over the next four Septembers, should reduce some of the uncertainty.
To collect data around Greenland’s entire coastline, the OMG team is using four bases. Slice two imaginary lines across the island, one north-south and the other east-west, and there’s a different OMG base for each quarter, more or less. The bases for measuring the west side of the island are on Greenland itself; for the east side, the bases are in Iceland and on the Norwegian island of Svalbard.
OMG isn’t moving methodically around the island. It’s spending a few days in one location and then another, sometimes doubling back to the first location, as logistics and weather dictate. An Earth Expeditions reporting team will catch up with the team in a few days from Iceland. For now, here are some images from the field, captured by the team members themselves.
Willis and the other OMG scientists timed this campaign to coincide with the Arctic sea ice minimum (conditionally announced on Sept. 10) so they would have the best chance of finding open water to drop probes into. But even at minimum, there’s still plenty of ice around Greenland. In loosely packed ice like this, dropping probes has been no problem. But in other locations, the water is almost completely covered with big plates of ice separated by narrow cracks, testing the team’s ability to hit their open-water targets. Some areas are completely ice-covered, with no possibility for dropping probes.
If you want to drop probes along the coast, you need to be able to see the coast. The weather doesn’t always cooperate. On this day, no data were successfully collected.
The probes are similar to those dropped by hurricane hunters to monitor the ocean during storms. There’s a parachute to waft the package safely to the ocean surface. When it hits the water, a float inflates to hold up a radio transmitter. A sensor, tethered to the transmitter by wire, sinks some 3,000 feet (if the water is that deep), measuring water temperature and salinity on the way down. The transmitter relays these data back to the aircraft. OMG will drop about 250 of these probes by the end of its deployment in early October. Combined with maps of the seafloor shape around the coast that OMG is also producing, the probe measurements will give a picture of where warm, deeper water can creep onto the continental shelf and eat away at the glaciers fringing the ice sheet.
To read more about OMG in the field: