A team of international researchers used MBARI’s advanced underwater technology to investigate and record changes in underwater landscapes in a remote Arctic region; focused on the effects of permafrost melting and new ice formation.

Researchers from the Monterey Bay Aquarium Research Institute (MBARI), collaborating with an international team, have discovered large underwater ice formations in a remote Arctic region off the coast of Canada’s Beaufort Sea. This finding reveals a previously unknown process that contributes to the long-term formation of underwater permafrost ice.

In a previous MBARI study, researchers observed massive craters on the seafloor in the region, linked to the melting of ancient permafrost underwater. Exploring the rims of these craters during a subsequent expedition, MBARI researchers and collaborators from the Korea Polar Research Institute (KOPRI), Korea Institute of Geology and Mineral Resources, Canadian Geological Survey, and U.S. Naval Research Laboratory observed the exposed layers. underwater ice of permafrost.

Formation of modern underwater permafrost ice

The newly discovered ice sheets are not the same as the ancient permafrost formed during the last ice age, but were formed under modern conditions. This ice forms when deeper layers of ancient underwater permafrost melt, creating salty groundwater that rises and refreezes as it approaches the seafloor, where the ambient temperature is about -1.4 degrees Celsius (29.5 degrees Fahrenheit).

The complex morphology of the seafloor in this region of the Arctic tells a story that involves both the melting of ancient permafrost that remained under the sea for long periods and the degradation of the modern seafloor that occurred as the released water refrozen.

After the last ice age, sea levels rose and covered ancient permafrost on the Arctic shelf. The base of this ancient mass of permafrost is slowly warming and thawing due to heat escaping from the Earth; much older, slower climate changes are causing this Arctic underwater permafrost to melt, not human-caused climate change. This water freezes as it moves towards the colder sea floor. Freezing ice creates ridges and ridges. Seawater seeps into the swollen surface of the seafloor, melting layers of ice and leaving behind large trenches. This process is driven by the dynamic interaction between large changes in salinity and small changes in temperature near the seafloor.

The research team published these new findings at: Journal of Geophysical Research: Earth’s Surface.

Implications for Arctic policy and infrastructure

“Our study shows that permafrost is actively forming and breaking down in large areas near the seafloor, creating a dynamic underwater landscape with large pits and large ice packs covered in sediment,” said Charlie Paul, MBARI geologist and lead author of the study. research. “These dramatic, ongoing seafloor changes have major implications for policymakers who make decisions about underwater infrastructure in the Arctic.”

MBARI has been part of an international collaboration to study the seafloor at the edge of the Canadian Arctic shelf since 2003. This remote region has only recently become accessible to scientists as high temperatures have caused sea ice to retreat.

A cartographic study conducted by Canadian researchers in 2010 revealed for the first time the distinctly sculpted topography of the region’s seafloor. In 2013, MBARI researchers and collaborators conducted the first high-resolution mapping studies in this region. The research team documented the seafloor topography in detail using MBARI’s Autonomous Underwater Vehicle (AUV).

Five mapping surveys, two from Canadian research vessels and three using MBARI’s advanced underwater technology, identified 65 newly formed seafloor craters in the region over a 12-year period. The largest crater was the size of a city block of six-story buildings.

The team returned to the Arctic in 2022 aboard the research icebreaker KOPRI. Aaron . They used MBARI’s two UAVs for the first time to map the seafloor to identify newly formed craters. They then conducted visual surveys of these craters using MBARI’s MiniROV. Designed by MBARI engineers, this portable remote-controlled vehicle can be configured for a variety of scientific tasks. This facility, equipped with cameras and sampling equipment, was an integral part of studying the Arctic floor. Researchers exploring the seafloor with MiniROV observed ice formation in two large craters that had recently formed on the seafloor.

Ice formation from brackish groundwater

Isotopic analysis of these formations and samples of surrounding seafloor sediments confirmed that the ice came from brackish groundwater formed partly by the melting of ancient permafrost rising from the seafloor. Rising groundwater refreezes near the seafloor, forming large sub-ice sheets that swell the seafloor and form ice mounds.

Small fluctuations in temperature and salinity cause an alternation between the freezing of rising salty groundwater and the melting of ice sheets near the seafloor. These continuous processes work together to create a spectacular underwater landscape consisting of numerous depressions and ice-filled mounds of various ages.

“These discoveries overturn our assumptions about underwater permafrost,” Paul said. “We previously thought that all underwater permafrost was remnants of the last ice age, but we learned that underwater permafrost is also actively forming and decaying on the modern seafloor.”

The process that creates these ice formations beneath the seafloor has not been considered before, and can occur when ground water temperatures are below zero degrees Celsius.

“This discovery means that the methods we previously used to detect underwater permafrost do not work for the type of seafloor ice we recently discovered in the Arctic. Now we need to look at where permafrost might be found beneath the Arctic shelf,” Paul said.