MITgcm helps uncover link between glacier melt and coastal productivity in Greenland.

Reporting by Helen Hill for MITgcm

A new study published in Communications Earth & Environment reveals how meltwater from Greenland’s most active glacier—Sermeq Kujalleq—triggers localized upwelling that boosts coastal productivity in West Greenland. Led by Michael Wood at Moss Landing Marine Laboratory, the study uses the ECCO-Darwin ocean biogeochemistry model, which is based on the MIT General Circulation Model (MITgcm), to simulate the complex interactions between glacial discharge, ocean mixing, and biological response.

The findings highlight a surprising consequence of ice sheet melt: the subglacial discharge from Sermeq Kujalleq appears to fuel a secondary summer phytoplankton bloom in Qeqertarsuup Tunua (Disko Bay), enhancing annual primary productivity in the region.

“Glacial meltwater isn’t just fresh—it’s buoyant and turbulent,” said Wood. “When it enters the fjord, it entrains deep, nutrient-rich water and brings it to the surface, much like upwelling systems elsewhere in the ocean.”

To quantify this effect, the team used the MITgcm-based ECCO-Darwin ocean biogeochemistry model and downscaled to 500-m grid spacing. This allowed them to simulate the vertical transport of nutrients and its impact on phytoplankton growth with unprecedented detail. The model showed that discharge-driven upwelling increases summer productivity by 15–40% in the fjord relative to a model with no discharge, though the annual carbon dioxide uptake rises by only ~3%, due to reduced solubility in warmer, plume-upwelled waters.

“The ECCO-Darwin model combines the powerful duo of ECCO ocean state estimates and the MIT Darwin ecosystem model, which allows us to mechanistically understand these intricate coupled ocean-ice-biology processes”, said co-author Dustin Carroll, the lead developer for ECCO-Darwin.

“The MITgcm was essential for capturing the fine-scale dynamics of the fjord system,” Wood said. “Its ability to resolve turbulent mixing and biogeochemical feedbacks made it possible to link physical processes to ecological outcomes.”

Sermeq Kujalleq, located near Ilulissat, is Greenland’s most prolific glacier, discharging over 40 gigatons of ice annually. During summer, meltwater from its vast drainage basin flows through subglacial channels and emerges at the grounding line, roughly 850 meters deep. As this buoyant water rises, it entrains deep fjord water, creating an upwelling flux estimated at over 45,000 cubic meters per second—nearly 40 times greater than the freshwater discharge alone.

This upwelling delivers nitrate, a limiting nutrient in Arctic waters, into the photic zone, alleviating nutrient stress and enabling a second bloom after the spring peak. The study’s simulations suggest that this mechanism could become increasingly important as ice sheet melt intensifies under future climate scenarios.

“Understanding these dynamics is critical for predicting how Arctic coastal ecosystems will adapt in the future as glacial melt will increase in response to climate change,” said Dutkiewicz, a primary architect of the Darwin ecosystem model who contributed to the biogeochemical modeling in this study. “Darwin and the MITgcm give us a powerful tool to explore these interactions across scales.”

While the enhanced productivity may benefit local food webs, the researchers caution that the long-term implications are complex. Changes in nutrient ratios, stratification, and carbon cycling could alter ecosystem structure and function in ways that are not yet fully understood.

The study underscores the importance of coupling physical and biological models to assess climate impacts in polar regions. By integrating glaciology, oceanography, and ecology, the team provides a holistic view of how Greenland’s melting glaciers are reshaping its coastal seas.

Questions/ comments email: mike.wood@sjsu.edu

Story Image: Green water alongside an iceberg that calved off Sermeq Kujalleq: Photo Credit: Aman KC, Boise State University

About the Researcher

Mike Wood is an assistant professor at Moss Landing Marine Laboratory, where he leads a Computational Oceanography lab. He holds a joint appointment with the San Jose State University Department of Computer Science. He is interested in “any topic that uses satellite observations, numerical ocean models, and/or in situ measurements to further our understanding of the ocean and its role in climate change.” His main research activities are currently focused on ice-ocean-biology interactions and sea level rise from the Greenland ice
sheet. He has been an MITgcm user for six years.

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