Ships Sail Waters Once Locked Under Antarctic Ice Shelf

A research ship has sailed through a narrow passage off the Antarctic Peninsula, an area once buried under a vast ice shelf and known among sailors as a death trap. The voyage happened in recent weeks, marking a first for modern vessels in waters exposed only after the sequential collapse of ice structures over the past 30 years. This stretch of the Weddell Sea was blocked by ice shelves that held firm for millennia but gave way starting in the mid-1990s due to rising air and ocean temperatures.

Background

Ice shelves along the east coast of the Antarctic Peninsula have thinned and broken apart one after another. The Larsen A shelf fell apart in 1995 after a period of warm weather and strong moisture flows from the north. Just seven years later, in 2002, the Larsen B shelf followed in a matter of weeks. That event saw huge chunks of ice shatter into the sea during the southern summer, when long daylight hours led to melt ponds on the surface. Those ponds filled cracks in the ice, widening them like wedges until the whole structure gave way.

The Larsen C shelf, farther south, lost a massive chunk in 2017. That iceberg, named A68, was bigger than the state of Delaware and drifted away after a rift grew for years. The remaining ice has shown changes since then, with the surface lowering and parts thinning from both above and below. Warm air from the west, pushed over mountains by winds, melts the top layers. At the same time, ocean currents warmed by climate shifts eat away at the underside.

These shelves float on the sea but act as barriers holding back glaciers from the land. When they go, the glaciers speed up and dump more ice into the ocean. The pattern of loss has moved south over time, matching a steady rise in regional temperatures. Data from satellites and aircraft show the ice has lost thickness and density, with less snow buildup and more melt.

Key Details

The recent ship passage went through what remains of the Larsen area, now open water where ice once dominated. Sailors and explorers avoided this zone for generations because of dense pack ice and towering shelves that could calve bergs without warning. Strong storms and waves battered the edges, but the ice held everything in place until recent decades.

Role of Atmospheric Rivers

Narrow bands of moist air, called atmospheric rivers, have hit the peninsula hard. These streams carry tropical moisture south and dump heavy rain and snow. About six in ten calving events on local shelves tie back to these events. They warm the air, cause surface melt, and break up sea ice that shields the shelves from waves. In 2002, a series of them struck Larsen B right before it collapsed. The same happened before Larsen A failed in 1995.

Researchers track these rivers with satellites and models. They link the events to broader warming, which makes the air hold more moisture. For Larsen C, the risk remains even though it sits in cooler waters. Speeding rifts and thinning ice signal trouble ahead.

"While the Larsen C Ice Shelf remains intact, we believe the same processes we observed in Larsen A and Larsen B will also impact Larsen C, posing a risk." – Jonathan Wille, researcher at Université Grenoble Alpes

The quote comes from Wille's review of data showing how these weather patterns build on long-term changes. Larsen C holds back enough ice to raise global sea levels by about one centimeter if it fully retreats. That matches the current rate of rise, which adds one centimeter every three years from expanding oceans and melting land ice.

What This Means

Open water here changes how ships move in the region. Research vessels can now reach spots once cut off, aiding studies of ocean life, geology, and climate records on the seabed. But it also points to faster ice loss inland. Glaciers that fed into lost shelves have sped up, thinned, and pulled back, adding to sea level rise. Some are still adjusting from collapses 30 years ago.

For Larsen C, models suggest the 2017 calving did not tip it over yet. But more events could weaken it step by step, like what happened to Larsen B. Warmer seas keep melting from below, while surface changes add stress from above. Winds shift sea ice away, letting waves hit harder.

This fits a larger retreat around the peninsula, seen since the 1990s. Past warm periods did not push ice loss this far south in 10,000 years. The ship passage shows how quickly the seascape has shifted. Teams watch rifts and flow speeds closely, ready for the next big break. Inland ice responds by flowing faster into open sea, a process that builds over years. Global oceans feel the effect as water volumes grow.