How Greenland’s melting ice fuels ocean life

As Greenland’s massive ice sheet continues to melt, it’s not just raising sea levels. The melting ice is also stirring up the ocean in ways that may be feeding tiny organisms at the base of the marine food chain.

The study behind this discovery comes from a team of scientists at San José State University, working in partnership with NASA’s Jet Propulsion Laboratory and the Massachusetts Institute of Technology.

Using powerful supercomputers and an advanced ocean simulation tool, the experts have shown how runoff from Greenland’s ice sheet may be helping phytoplankton thrive. These tiny, plantlike organisms are critical to life in the ocean – and to the planet’s climate.

Melting ice is feeding the ocean

Greenland’s ice sheet, which is over a mile thick in places, is losing around 293 billion tons of ice each year. In the summer, meltwater pours into the sea at astonishing rates.

From the base of Jakobshavn Glacier (also known as Sermeq Kujalleq), more than 300,000 gallons of fresh water enter the ocean every second.

This freshwater doesn’t just disappear. It creates a plume that rises up through the saltwater, and as it does, it appears to carry nutrients from deep in the ocean toward the surface.

Scientists have long suspected that this upwelling may help feed phytoplankton, especially during the summer when surface nutrients run low.

The role of phytoplankton

Phytoplankton play a big role in Earth’s systems. They absorb carbon dioxide and form the base of the food web for everything from krill to whales. Despite being microscopic, they’re essential to marine ecosystems across the globe.

NASA satellite data has shown a 57% increase in phytoplankton growth in the Arctic between 1998 and 2018.

The timing of this growth spike led researchers to think glacial melt might be part of the reason. But proving it has been difficult, especially in Greenland’s remote, iceberg-filled fjords.

A hidden ocean world

Dustin Carroll is an oceanographer at San José State University who is also affiliated with NASA’s Jet Propulsion Laboratory in Southern California.

“We were faced with this classic problem of trying to understand a system that is so remote and buried beneath ice,” said Carroll. “We needed a gem of a computer model to help.”

The model came in the form of ECCO-Darwin, a tool developed at JPL and MIT. It’s been described as a virtual ocean laboratory.

This tool pulls together decades of data – billions of measurements from satellites and ocean instruments – to simulate how water, heat, salt, nutrients, and life interact across the globe.

Meltwater and phytoplankton growth

Michael Wood, a computational oceanographer at San José State University, noted that simulating how biology, chemistry, and physics interact in just one corner of Greenland’s 27,000-mile coastline is an enormous mathematical challenge.

Wood said that to break it down, they built a “model within a model within a model” to zoom in on the details of the fjord at the foot of the glacier.

The calculations, run on NASA’s supercomputers in Silicon Valley, showed that glacial meltwater could increase summer phytoplankton growth by 15 to 40% in the fjord they studied.

More ice, more impact

It’s too soon to say exactly what this means for Greenland’s marine ecosystems, but it’s clear that changes in the ice are driving changes in the water.

“Melt on the Greenland ice sheet is projected to accelerate in coming decades, affecting everything from sea level and land vegetation to the saltiness of coastal waters,” Carroll said.

“We reconstructed what’s happening in one key system, but there’s more than 250 such glaciers around Greenland.” The team plans to expand their simulations to other coastal areas.

Broader implications of the study

The researchers also looked at how these changes affect the ocean’s ability to absorb carbon dioxide. In the fjord, meltwater makes the seawater less able to dissolve carbon.

But that loss seems to be canceled out by the larger phytoplankton blooms, which take in more carbon dioxide from the atmosphere through photosynthesis.

“We didn’t build these tools for one specific application,” said Wood. “Our approach is applicable to any region, from the Texas Gulf to Alaska. Like a Swiss Army knife, we can apply it to lots of different scenarios.”

Image Credit: NASA’s Scientific Visualization Studio

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