Where does Antarctica's melted ice go? MBARI's first-ever electromagnetic survey probes the seafloor's 'plumbing'

When Antarctic ice melts, where does the water go?

Into the sea. Obviously. But that is not the whole story.

Some of the meltwater seeps into the ground beneath the seafloor. Down there, groundwater and gas flow through what MBARI's Aaron Micallef calls an 'underground plumbing system.' The problem: nobody knows how warming is changing that plumbing.

Antarctica's first electromagnetic survey

In January 2026, a seven-day expedition aboard Spain's polar research vessel Hespérides set out to 'see through' the Antarctic seafloor using electromagnetic waves.

The tool was CSEM — controlled-source electromagnetics. It sends electromagnetic pulses into the seafloor and reads the return patterns to map ice, groundwater, and gas. Range: 40 kilometres. It had never been used in Antarctica before.

What three sites revealed

Surveys were conducted at Deception Island, King George Island, and Astrolabe Trough.

All three sit in the Bransfield Basin off the Western Antarctic Peninsula — one of the Southern Hemisphere's fastest-warming regions. The team extracted porewater from sediment cores to look for traces of melted ice.

Life on the Antarctic seafloor

Footage captured during the survey was striking.

Brown gelatinous sea squirts, yellow sponges, branching orange sponges, pink sea urchins, orange sea stars. The Antarctic seafloor is far more colourful and alive than you might expect.

What the researcher says

Beneath Antarctica's seafloor, groundwater and gas move through what is essentially an underground plumbing system. These systems are incredibly important, but their processes remain poorly understood.

— Aaron Micallef (MBARI Senior Scientist, expedition leader)

It will take months to fully interpret what we mapped and sampled here.

— Aaron Micallef

For Arctic ice changes, see 'The Ice Protecting Alaska Is Vanishing Faster Than Expected.'

A note from the author: The phrase 'underground plumbing system' stuck with me.

When ice melts, the water doesn't just flow into the sea. It also seeps into the ground beneath the seafloor. What happens down there is still largely unknown.

The lead researcher mentioned that the most interesting science happens when plans change. That line stayed with me.