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Polar Region Seafloor Mapping

Why Seafloor mapping?

A picture is worth a thousand words. Similarly, mapped information is the visual representation of raw data. Generally speaking, seafloor mapping presents unique challenges that are not seen when mapping land.

Due to the remoteness of polar regions, there has been a considerable amount of uncertainty about the marine realm. Climatic changes due to rising sea temperatures, reducing the oxygen content of bottom waters and increasing depth, make studying of this changing landscape crucial. This data can be put under a regressed climatic scenario to make future predictions. Scientists can then carry out an analysis of the dataset to create a detailed map. 

Arctic Seafloor

Arctic sea ice in the summer of 2022 has reached a minimal level, aligning itself with other low records of the previous decade.

The above image demonstrates the retreated icecap over years in the arctic region.

Due to the above-average temperatures in the Arctic this year, the sea ice has seen its 10th lowest level in the past 43 years. Seabed mapping of the Arctic region has revealed some stunning imagery that shows how the terrain has changed as a result of the regular thawing of glacial mass. 

High-resolution bathymetric surveys have been conducted using autonomous mapping robots. A team of scientists has recorded several sinkholes-like valleys that are as large as the size of a city with six-story buildings. Such deep basins have formed in less than a decade. These dramatic changes in the Arctic terrain are unprecedented. 

Repeated surveys with MBARI’s mapping AUVs revealed dramatic and rapid, changes to seafloor bathymetry from the Arctic shelf edge in the Canadian Beaufort Sea. This massive sinkhole developed in just nine years. Image: Eve Lundsten © 2022 MBARI

Brackish water generated due to the thawing glacier gets collected exactly at the bottom layer of the ice sheet, which speeds up the melting process of the remaining permafrost. Newly formed cavities fill up with water where there was once an iceberg. When a melting permafrost-filled subsurface doesn’t have enough ice to stand, it collapses and creates large sinkholes on the seafloor. In the image shown above, a bathtub-looking sinkhole has formed over years of melting ice, just that it is thousands of times bigger than a bathtub.

MBARI’s mapping AUVs detailed the unusually rough seafloor terrain along the edge of the continental shelf in the Canadian Arctic. Sinkholes have developed where permafrost ice at depth has thawed, forming voids into which the seafloor collapsed. The circular mounds formed where the brackish water produced from the relic permafrost decay has migrated upwards and frozen, blistering the seafloor with ice-cored mounds called pingos. Image: Eve Lundsten © 2022 MBARI

Studying this colourful map above has also revealed one interesting fact: many “pingos” have been observed on the seabed. Though it sounds like a fun-loving children’s game, it is a hill-like formation that is typically cone-shaped and grows in the icy region on a regular basis. It is formed when the brackish water refreezes as it approaches the colder seafloor level. This is due to the bottom ocean water keeping the near seafloor cooler. When the ice in the near-seafloor residue freezes, it expands, creating pingos—circular hills with an interior of ice. The maps have documented plenty of pingos that have formed adjoining the discharge areas. 

With the incredible speed at which the seabed is changing, it is extremely critical to understand how the retreating ice in the Arctic is going to impact the sea level worldwide.

Antarctica seafloor

Antarctic sea ice extent, on 19 September 2022. The orange line shows the 1981-2010 average extent for that day. Credit: NSIDC.

The least populated continent on the planet. Known for its icy, windiest, and driest climatic conditions, it is highly sensitive to the rising global temperature. Antarctica, like its northern sister, is not immune to the dangers of climate change. Recently, the western part of Antarctica was under scrutiny because of the massive glacier called “Thwaites Glacier” that is located there.

Thwaites Glacier, western Antarctica

As big as the state of Florida, US, it is the widest glacier in the world. Researchers from the United States, U.K., and Sweden installed an autonomous underwater robot called Rán (Kongsberg HUGIN, at the University of Gothenburg) to map the closest region of “Thwaites”.


3D view of multi-beam bathymetry

At the end of the 20 hours of seafloor mapping, less than half a mile underwater in front of the glacier, precise high-resolution multi-beam 3D imagery was produced by the robot. The imagery above shows that the iceberg has left behind footprints where it was originally standing.

Marine Scientist Alastair Graham (University of South Florida), states that “Thwaites” has retreated in the last six months; however, it is unclear to state when it actually occurred.

“(It could have been) maybe 200 years ago, or maybe even more recently in the mid-20th century, so the 1940s or 1950s when we weren’t even watching Thwaites,” Graham said. “But it was going back at a rate that’s at least twice what it’s retreating at right now.”

In the past, the front edge of the iceberg has lost its touch with the seabed ridge and consistently lost its ice at the rate of 2.1 kilometers per year. This pace has doubled from what was observed using satellite images from 2011 to 2019. It is highly probable that Thwaites might retreat at a faster pace than earlier due current climate change crisis.

Also, Graham further analyzed the sonar scan photos using computer simulation models and documented that 700 meters underneath the ocean floor are a set of immersed footprints or rib-like prints that were created by the tidal movement of the iceberg shaking up and down. Each rib line suggests each day’s retreat.

A side-scan seabed image showing the newly discovered ribs at the seafloor, created as Thwaites retreated back across the seabed. Alastair Graham/University of South Florida

Factually, Thwaites is considered to be an unstable glacier in Antarctica, according to the International Thwaites Glacier Collaboration. The reason is that it sits on a rock, which is in the interior of Antarctica. Gradually, as the glacier retreats further, more dense parts of the ice will be exposed to the ocean water. That is a dangerous event as it will lead to more ice melting.

Over past centuries, Thwaites has been holding on to so much ice that if it melts completely, the global sea level is expected to jump up at least 10 feet. Sea level rise throughout the coastline will not be as linear as overflowing pots. On the contrary, it is expected to drop in the areas where there will be a major ice loss, and it is going to rise drastically in the tropical region. So, are we ready to redraft our coastlines in the future?