Source: Journal of Geophysical Research: Oceans
As marine-terminating glaciers melt, the resulting freshwater is released at the seafloor, which mixes with salty seawater and influences circulation patterns. As the oceans warm, it’s growing increasingly important to study this process. Researchers do so using the framework of buoyant plume theory, which describes how rising freshwater interacts with denser salt water. Falling chunks of ice, which can easily crush boats, make working near glaciers dangerous. Thus, empirical data that can verify buoyant plume theory have rarely been collected.
Ovall et al. helped fill this gap by using remotely operated kayaks equipped with instruments to monitor the features of water flowing out from Xeitl Sít’ (also called LeConte Glacier) in southeastern Alaska. Their work marked the first time researchers took measurements of a plume’s size, shape, and velocity from directly above the upwelling plume.
The robotic kayaks allowed the researchers to observe the plume of rising freshwater without risking their own safety. Instruments aboard the kayaks sent acoustic signals downward, which bounced off particles within the rising plume to measure its velocity.
The volume and characteristics of the rising plume of water are substantially different from those predicted by buoyant plume theory, they found. The study’s measurements found that upwelling water moves at rates of more than a meter per second. Buoyant plume theory doesn’t capture the extent to which freshwater pulls salt water into the rising plume, leading researchers to underestimate the volume of the plume by as much as 50%. That mismatch likely arose in part because scientists underestimated how the shape of a glacier’s submarine portion affects the interaction between freshwater and ocean water. However, the authors note, there are likely other factors at play that have not yet been identified. (Journal of Geophysical Research: Oceans, https://doi.org/10.1029/2025JC022902, 2025)
—Saima May Sidik (@saimamay.bsky.social), Science Writer
