In a world-first, an undeclared type of ice loss in the Arctic has been measured

Globally, the loss of sea ice can cause more intense heat waves and the release of vast quantities of greenhouse gases due to permafrost thawing- not to mention wildlife endangerment due to a loss of habitats and coastal flooding. Developing accurate models of global glacial mass loss in an uncertain climate, therefore, makes sense.

Researchers become the first to map and quantify ice loss in the northern hemisphere

Yet, a type of ice loss known as frontal ablation, when chunks of ice (including icebergs) break off from the edge of a glacier, remains largely "unquantified" in most glacial models. Now a pair of researchers, William Kochtitzky and Luke Copland, from the University of Ottawa in Ontario, Canada, are the first to map out all of the glaciers that end in the ocean in the northern hemisphere, estimating their pace of change over the previous 20 years.

They, along with an international team, are also the first to publish a comprehensive quantification for frontal ablation - starting with the polar region.

Interesting Engineering (IE) spoke with one of the two researchers, William Kochtitzky, to find out more.

More than 1700 glaciers have direct contact with the ocean in the northern hemisphere

William Kochtitzky and Luke Copland are on a mission to bring more understanding of how and why marine-terminating glaciers are changing and have been the lead researchers of two published studies this year (2022)- the first of which they were the sole authors.

In their first study this year, the pair highlighted that in the Northern Hemisphere, more than 1700 glaciers have direct contact with the ocean. Some float, whereas others are grounded to the seabed below with their glacier front extended out into broad, flat ice shelves.

On this note, they claim that almost all of these ice sheets are in retreat due to frontal ablation. In other words, they are losing mass by calving icebergs and releasing them into the ocean.

The 'first-of-its-kind' analysis was aided by good old-fashioned tracing of glacier fronts in 2000, 2010, and 2020

"The simplest way to think about frontal ablation is like discharge from a river. You need to measure the depth all across the river and the water velocity, then you can calculate the discharge," explained William Kochtitzky to IE.

"This is exactly what we do with glaciers in measuring frontal ablation except it is a little more complicated since ice melts and glaciers advance and retreat, but those are just details."

One highlight from their initial study was that part of their approach involved manually tracing the location of each glacier's front in 2000, 2010, and 2020 using photos from satellites such as Landsat 8 and Terra. To calculate rates of ice mass change, they took into account changes in the glacier's end position and combined this with measurements or estimates of ice thickness as well as surface velocity.

Their second study (Kotchtitzy et al.) focused on continuing the quantification of frontal ablation rates and took a similar approach. Kotchtitzy explained to IE, "We mostly used satellites, but also aircraft that have flown over these glaciers used radars to take thickness measurements. We also used glacier models to tell us variables that we don't know or have not measured yet."

Since 2000, the northern hemisphere has lost almost 6.6 times the area of Manhattan in ice due to frontal ablation

From this methodology, the duo discovered in the first of their two studies, which included the Greenland ice sheet, that 85 percent of the glaciers had receded throughout these two decades.

They concluded that there was a total ice loss of approximately 7,500 square kilometers (2,900 square miles) over this time. In a press release, Kochtitzy described this as more than 1 kilometer square (km2) per day, which is "6.6 times the area of Manhattan."

"Over the last 20 years this adds up to more a little more than half the size of Prince Edward Island, Canada, the US states of Delaware and Rhode Island combined, or about 3 times the size of Luxembourg," he added.

The second study of the two revealed similar chilling conclusions. Kochtitzy et al found that from 2010 to 2020, over 1,500 glaciers in the Northern Hemisphere (excluding the Greenland ice sheet) together lost 52 gigatonnes of ice annually through frontal ablation.

Their findings also reveal that from 2000 to 2020, ice loss by frontal ablation was equivalent to a 2.10 mm sea-level rise, and suggests that this process is the most significant contributor to ice mass loss in some regions.

Chilling 'hotspots': The Greenland Periphery and Arctic Russia are among the most susceptible areas

Of all the study areas in the northern hemisphere, the researchers concluded that the Greenland Periphery had 537 marine-terminating glaciers accounting for the most losses (62 percent).

This is the area surrounding the large Greenland ice sheet. It's home to smaller ice caps (such as Maniitsoq and Flade Isblink) and glaciers covering between 76,000 and 100,000 square kilometers (29,000 and 39,000 sq miles).

As can be seen from the photo above, intense changes occurred at the Zacharaie Isstrøm which is in northeast Greenland. The researchers concluded that this area alone lost 1,453 square kilometers (561 square miles) of ice between 2000-2020.

"The changes at Zachariae Isstrøm in Greenland are incredible," Kochtitzky said to NASA. "It lost 73 square kilometers per year. That is nearly six times more than the glacier with the second-most area loss."

Kochtitzky et al highlighted other areas, or "hotspots," for marine-terminating glaciers and ice shelves outside the Greenland periphery. The team indicated that the coastal regions most susceptible to ice loss by frontal ablation are those in the Russian Arctic, Svalbard, and Alaska.

Putting numbers to the now-collapsed Matusevich Ice Shelf in Arctic Russia

To arrive at figures for these 'hotspot' regions, the researchers produced an intensity index. Essentially, on a grid of 10 kilometers, the index spatially combined all frontal ablation from glaciers occurring within 50 kilometers of any point in the ocean.

Both the frontal ablation rates and the number of glaciers close to a given area affect the index. The study explained that the ice loss, therefore, fluctuates in a manner that is broadly consistent with the spatial variation seen in the frontal ablation of glaciers in each ocean region.

They discovered that the Matusevich Ice Shelf in Arctic Russia showed exceptionally high-intensity indices, indicating hotspots of potential iceberg occurrence. In fact, the eight glaciers that fed the now-collapsed Matusevich Ice Shelf in Arctic Russia had the highest frontal ablation rate in the Northern Hemisphere besides Greenland.

You can see how this makes sense if you look at the image above, which was captured by Landsat 8 using NASA's Operational Land Imager (OLI).

Kochtitzky concluded that the Matusevich Ice Shelf in Arctic Russia lost roughly 160 square kilometers (62 square miles) of ice between 2000 and 2020 as iceberg break-offs (frontal ablation).

"The main thing that surprised me is that frontal ablation is bigger by mass than all the melt in Arctic Russia."

"The main thing that surprised me is that frontal ablation is bigger by mass than all the melt in Arctic Russia and most likely Svalbard as well, Kochtitzky revealed to IE. "This means that more ice is lost as icebergs than as meltwater."

While the studies are the first to quantify this type of ice loss, it's also worth noting the complex nature of ice sheets. That is, they are constantly retreating and advancing. It's all part of the way in which Earth's changing systems are dynamic.

Each marine-terminating glacier advances and retreats under specific conditions, depending on elements like contact with the seafloor or the geometry of a fjord. For example, the Columbia glacier in Alaska pictured below lost 3 square kilometers per year from 2000-2020 as it underwent dramatic retreat due to an unstable geometry beneath the glacier.

Moreover, glacial fronts may become more exposed when there is less sea ice next to the shelf. Warm air and water temperatures, which melt a shelf from above and below and cause it to shrink and weaken, can potentially cause a collapse.

'The marine-terminating glaciers lost contact with the ocean and became land-terminating'

Still, the studies do reveal some patterns in the Northern hemisphere. For instance, "In all, 123 glaciers that ended in the ocean in 2000 now end on land," confirmed Kochtitzky, regarding the first study.

Additionally, the team of the second study concluded that 49 marine-terminating glaciers lost their connection to the sea between 2000 and 2010. Another 120 glaciers followed in the next ten years.

"No one had a number to use in these calculations. We now provide that number."

Either way, the updated inventory of glacier front positions and an estimate of their frontal ablation rates could come in handy as data included in future climate assessment reports, like those published by the Intergovernmental Panel on Climate Change (IPCC).

"Our study is primarily important in informing other studies on glacier mass balance," Kochtitzky told IE. "This really critical and large mass balance term had never been quantified before, so no one had a number to use in these calculations. We now provide that number," he added.

Moreover, the approach to identify 'hotspots' for frontal ablation will yield a better understanding of the glaciers, and therefore regions, that are most susceptible to iceberg hazards and marine ecosystem impacts.

Next steps: Quantifying the unquantified in Antarctica

"We have already completed a similar study on Greenland, which we hope will be published soon. Next, we hope to continue this work in Antarctica, where this work has not been done before.