As the ice in Greenland retreats, it brings a new source of nutrition for tiny organisms. To test why, scientists turned to a computer model developed by JPL and MIT that has been called a laboratory in itself. Simulation by NASA shows that meltwater from Greenland’s Jakobshavn Glacier lifts deep-ocean nutrients to the surface. This leads to an explosion in the summer bloom of phytoplankton that feed the Arctic food chain.
Using NASA’s ECCO model, a data visualization has been created that shows that ocean currents swirl around North America and Greenland. State-of-the-art computing techniques help oceanographers find phytoplankton hotspots.
Greenland’s ice sheet runoff is pushing nutrients up from the depths of the ocean, boosting phytoplankton growth. To simulate the complex interactions of marine life and physics in a single chaotic fjord, scientists have used advanced computing. Oceanographers are interested in finding what drives these tiny plantlike organisms that take up carbon dioxide and support the fisheries worldwide.
Some 293 billion tons (266 billion metric tons) of ice per year is shed by Greenland’s mile-thick ice sheet. More than 300,000 gallons (1,200 cubic meters) of fresh water drain into the sea every second from beneath Jakobshavn Glacier during peak summer melt.
The meltwater plume is more buoyant, less dense, and fresher than the surrounding saltwater. According to scientists, this rising water might be delivering nutrients like iron and nitrates, which are essential for the phytoplankton floating at the surface.
Although smaller than the eye of a needle, phytoplankton interest researchers because they are titans of the food chain. Krill and other critters feed on phytoplankton, which supports whales and fish in the food chain.
NASA’s satellite data previously recorded a 57% increase in the number of phytoplankton between 1998 and 2018 in the Arctic waters. A mixture of nitrate from the depths would be vital to Greenland’s phytoplankton in summer, because almost all nutrients are consumed by the previous spring bloom. Long-term observations and hypotheses have been challenging to test due to the presence of rough terrain and icebergs as big as cities along the coast. According to Dustin Carroll, an oceanographer at San José State University who is also affiliated with NASA’s Jet Propulsion Laboratory in Southern California, the scientists are facing the classic problem of understanding what’s going on beneath the ice.
The team harnessed a model of the ocean developed by scientists at JPL and MIT to simulate what was happening in the waters around Greenland’s most active glacier. The model uses nearly all available ocean measurements carried out by sea- and satellite-based instruments. This gives billions of data points, from water temperature and salinity to pressure at the seafloor. The model has been named Estimating the Circulation and Climate of the Ocean-Darwin (ECCO-Darwin for short).
Simulating biology, chemistry, and physics all in one system along the 27,000 miles (43,000 km) of Greenland’s coastline is a massive math problem. To break it down, the team needs to build a model within a model within a model to pinpoint the details of the fjord at the foot of the glacier. Using supercomputers at NASA’s Ames Research Center in Silicon Valley, the team of scientists calculated that deepwater nutrients were pushed upwards by glacial runoff. This would be enough to boost the growth of phytoplankton during summer bloom by 15% to 40% in the study area.
The question arises: could increased phytoplankton growth be a blessing in disguise for Greenland’s marine animals and fisheries? According to Carroll, uncovering ecological effects will take time. Melt on Greenland is going to increase in the coming years, affecting the seawater level, land vegetation, and saltiness of coastal waters, among other factors.
“We reconstructed what’s happening in one key system, but there are more than 250 such glaciers around Greenland,” Carroll said. He commented that the team plans to extend their simulations to the whole Greenland coast and beyond.
Some changes are affecting the carbon cycle both positively and negatively. The team measured how runoff from the glacier changes the chemistry and temperature of the seawater in the fjord. This leads to less dissolution of carbon dioxide in the ocean. However, the loss is canceled out by the bigger blooms of phytoplankton taking up more carbon dioxide from the air as they photosynthesize.
The team wants their model to work across various regions, from Texas to Alaska. They want their model to work in different scenarios like a Swiss army knife.
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