Iceberg Melt Rates and Glacier Frontal Ablation: Seller and Heim Glacier, Antarctica

This post originally appeared on the AGU blog From a Glacier’s Perspective and was written by Mariama Dryak.

Figure 1: Study sites considered in this article: Seller Glacier and Heim Glacier. Landsat-8 image courtesy of the U.S. Geological Survey

Iceberg melt is caused by the temperature of the water in which an iceberg floats and the velocity of the water flowing around the iceberg. As a result, iceberg melt is an excellent indicator for the ocean conditions in which an iceberg resides. Given the remote location of Antarctica, and the difficulty in taking direct oceanographic measurements immediately in front of glacier termini in Antarctica, icebergs near glacier fronts can act as a useful proxy for what the ocean conditions are in these areas, especially under changing climate.

Dryak and Enderlin (2020) compared remotely-sensed iceberg melt rates (2013 – 2019) from eight study sites along the Antarctic Peninsula (AP) to glacier frontal ablation rates (2014 – 2018) where they overlapped in time and found a significant positively correlated relationship between the two. In general, iceberg melt rates were found to be much lower on the eastern AP where ocean waters are characterized as very cool relative to the heterogeneous, but generally warmer, waters on the western AP–where iceberg melt rates were higher. When we take a closer look at the data and consider what this means in the context of a stratified water column, the iceberg melt rate magnitudes also make sense relative to one another and what is known of regional ocean conditions.

Here we take a look at the results from two of those study sites: Seller Glacier and Heim Glacier.

Seller Glacier is the southernmost study site considered in our study on the Antarctic Peninsula, and produces very large, sometimes tabular icebergs with relatively high mean melt rates. Figure 2 indicates the changes in the same iceberg at two points in time. These icebergs are larger than and different in style to all of the other study sites, with the Seller Glacier terminus also being the widest of all the glaciers considered in the study. Due to the large area of the icebergs produced, we know that the keel depths of these icebergs also extend deep into the water column (See Table 1, Dryak and Enderlin, 2020), contacting warm subsurface waters (and some contacting Circumpolar Deep Water (CDW)) as characterized by Moffat and Meredith (2018) in Figure 3 below. In the upper layers these icebergs also sit in the very cold Winter Water (WW) layer and expanded section of Antarctic Surface Water (AASW) prevalent in the Seller region.

Figure 2: An iceberg from Seller Glacier in 2014 and later in 2016. Mean submarine melt rates for the Seller Glacier icebergs from this time period were 6.54 cm/day. Imagery © [2019] DigitalGlobe, Inc.

Frontal ablation rates at Seller Glacier are higher than expected given iceberg melt rates at the other sites on the western Antarctic Peninsula (Figure 4). Dryak and Enderlin (2020) suggest this to be because of a long-term dynamic adjustment of the Seller Glacier in response to the collapse of the Wordie Ice Shelf, which occurred between 1966 and 1989 (Vaughan, 1991)-a similar case to the sustained elevated velocities witnessed at Crane Glacier on the eastern Antarctic Peninsula following the collapse of the Larsen B Ice Shelf in 2002.

In contrast, the study site at Heim Glacier, north of Seller Glacier, contains smaller, shallow icebergs with low iceberg melt rates on par with iceberg melt rates found on the eastern Antarctic Peninsula. The glacier that produced the sampled icebergs, though not the smallest of the sites sampled, produces icebergs small in area that often do not last from one season to the next. The keel depths of the sampled icebergs at Heim Glacier likely do not reach below the cold WW layer (Table 1, Dryak and Enderlin, 2020), terminating in the very cold water layer or above in the compressed and comparatively cool AASW. However, the Heim study site is also located near the Marguerite Trough, an area of deep bathymetry known for the presence of warm waters, so the low melt rates here may be surprising to some without taking a closer look at the specific locale. Our study suggests that the bathymetry of the area in which the icebergs reside might be sheltered due to the presence of Blaiklock and Pourquoi Pas Islands, which may deflect warmer waters from reaching the Heim Glacier.

Figure 4:  Scatterplot of iceberg melt rates and frontal ablation for nearby glaciers over near-coincident time periods. Symbols indicate median frontal ablation rates. Figure 8 from Dryak and Enderlin (2020)

Frontal ablation rates at Heim Glacier are low, and of a similar magnitude to eastern Antarctic Peninsula sites, corresponding in magnitude to the low iceberg melt rates for the site as well (Dryak and Enderlin, 2020; Figure 8).

Overall, this paper re-emphasizes the importance of considering the ocean’s role in forcing changes on glaciers that terminate in the ocean around Antarctica, especially under changing climate. With the ocean acting as a large sink for excess heat in the atmosphere, evaluating the consequences of the storage of this heat in the ocean is essential when attempting to understand the feedback mechanisms associated with such change. The moral of the story is that we must keep one eye on the ocean going forward and how it could lead to changes in glacier dynamics, which could lead to changes in the contributions of glaciers to sea level and the marine ecosystems that exist within the ocean.

For full results and discussion of all of the study sites considered along the western and eastern sides of the Antarctic Peninsula, read the full Dryak and Enderlin (2020) article in the Journal of Glaciology.

*Note the Seller Glacier like many others in the region have experience rapid retreat in the last 30 years, Fleming Glacier, Sjogren Glacier and Boydell Glacier.

Read More on GlacierHub:

A Minority of Peruvian Mountain Farmers Benefit From Government Pandemic Programs

No Change in Black Carbon Levels on Peruvian Glaciers, Despite Pandemic Quarantine

Video of the Week: Coronavirus Protests in Pakistani Karakoram

Off with the Wind: The Reproduction Story of Antarctic Lichens

How do organisms begin new life at the bare surfaces exposed by glacier retreat? A team of researchers from the Czech Republic recently published a paper on the spread of one organism, a lichen, across James Ross Island near the Antarctic Peninsula. The study found that lichens can disperse over long distances, likely by means of aerial transport. Increasing warming trends on James Ross Island will likely result in more deglaciation, providing species like lichens with the opportunity to colonize new areas.

Usnea sp Lichen on James Ross Island (Source: Elster Josef)
Usnea sp Lichen on James Ross Island (Source: Elster Josef).

There has previously been considerable debate on the reproductive and dispersal mechanisms of lichens, especially in the polar regions. The study’s findings on lichen reproduction is promising, given the important role lichens play as primary successors, contributing to soil development and the establishment of ecosystems with greater biomass and biodiversity. Combining an alga and a fungus, the lichen can grow on almost any surface, from sea level or high altitudes to the side of trees or on rocks. Lichens are also able to reproduce both sexually (through propagules, which are small, vegetative structures that get detached from the parent plant) or asexually (mini-lichens), and are transported by wind, sea currents or birds.

GlacierHub spoke with lead author Elster Josef from the Center of Polar Ecology about the study. He asserts that one of the most distinctive features of James Ross Island is the island’s so-called volcanic mesas, which are favorable locations for biomass growth. Volcanic mesas originate from superimposed subglacial volcanic eruptions and are characterized by a relatively flat highland with steep edges. Usnea sp., a lichen commonly known as the old man’s beard, is the most important lichen in this system. “It produces dense carpets in the oldest volcanic mesas. This species has many advantages in respect of dry local climate,” Josef said.

Overview of James Ross Island with its volcanic mesas (Source: Elster Josef)
Overview of James Ross Island with its volcanic mesas (Source: Elster Josef).

There is a clear gradient of lichen cover and diversity from north to south on James Ross Island, according to Josef. One important question of the research was how this lichen carpet advances with glacier retreat. Josef stated that his team was able to successfully develop a non-invasive method to measure lichen carpet diversity and biomass. Traps in the form of petri dishes fixed to rock surfaces with stick tape were the simplest and most effective way for the team to measure lichen dispersal across the island, according to Josef. A total of 100 traps were placed during the summer season of January/February 2008 and left exposed for a year. In the end, only 60 traps were found due to snow cover and strong wind disturbance.

For the Antarctic lichens, vegetative asexual reproduction was found to be more dominant due to environmental stresses. While the old man’s beard and the Leptogium fungus (Leptogium puberulum) were the two most common local species on the island, their frequency of occurrence in the traps was unrelated to local species dominance. Long-distance dispersal of vegetative parts occurs more frequently on the larger scale as a result of wind conditions.

Lichen Spore/Fragment trap designed for the research using sticky tape in a petri dish(Source: Elster Josef)
Lichen Spore/Fragment trap designed for the research using sticky tape in a petri dish (Source: Elster Josef).

Surface wind speeds on the mesas are often higher than 6m/s (roughly 12 mi/hr) on average, with extremes reaching up to 30m/s (60 mi/hr). Larger amounts of lichen spores and fragments were found in the traps located along the prevailing wind direction. Overall, the highest occurring species in the traps were of foliose and fruticose growth types, which favored wind dispersals.

The main difficulty of the research method was that the dispersal of lichens is influenced by many abiotic and also biotic factors, according to Josef. These include distance from glaciers and elevation to existing lichen diversity and cover on site. The method was also limited because it did not involve measurements of what is viably ready (in-situ) to start growth and only measured what types of lichens were dispersed.

A team member collecting the samples on the sticky tape after the trap was exposed for a year (Source: Elster Josef)
A team member collecting the samples on the sticky tape after the trap was exposed for a year (Source: Elster Josef).

The greatest confirmation to the team’s hypothesis was the strong positive correlation between the size of clast, or rock fragment, and the dispersed species assembly. Clast size is determined based on the average diameter of rocks in the area. Often, areas with larger clast size are characterized by a thriving diversity of lichen communities. They represent more stable locations for growth since larger stones shield the newly-trapped lichen fragments from being uprooted by the wind again.

Still, according to Josef, lichen development is rather rare despite the large numbers of reproductive fragments dispersed. The growth of a lichen community is a long-term process, and Josef hopes to continue to evaluate the reaction of lichens to climate change in polar regions to shed light on the colonization mechanism of pioneer species in newly-exposed surfaces.

Roundup: Grounding Lines, Methane-Oxidizing Bacteria and Grazing Patterns

Grounding Lines of Antarctic Glaciers Show Fast Retreat

From Nature Geoscience, “Grounding lines are a key indicator of ice-sheet instability, because changes in their position reflect imbalance with the surrounding ocean and affect the flow of inland ice. Although the grounding lines of several Antarctic glaciers have retreated rapidly due to ocean-driven melting, records are too scarce to assess the scale of the imbalance. Here, we combine satellite altimeter observations of ice-elevation change and measurements of ice geometry to track grounding-line movement around the entire continent, tripling the coverage of previous surveys. Between 2010 and 2016, 22%, 3% and 10% of surveyed grounding lines in West Antarctica, East Antarctica and at the Antarctic Peninsula retreated at rates faster than 25 m yr−1 (the typical pace since the Last Glacial Maximum) and the continent has lost 1,463 km2 ± 791 km2 of grounded-ice area.”

Discover more about Antarctica’s melting situation here.

The calving front of an ice shelf in West Antarctica as seen from above (Source: NASA/Flickr)


Glacier Melt Exposes Land for Methane-Oxidizing Bacteria

From Oxford Academic: “Methane (CH4) is one of the most abundant greenhouse gases in the atmosphere and identification of its sources and sinks is crucial for the reliability of climate model outputs. Although CH4 production and consumption rates have been reported from a broad spectrum of environments, data obtained from glacier forefields are restricted to a few locations. We report the activities and diversity of Methane-Oxidizing Bacteria along a Norwegian sub-Arctic Glacier Forefield using high-throughput sequencing and gas flux measurements. The overall results showed that the methanotrophic community had similar trends of increased CH4 consumption and increased abundance as a function of soil development and time of year when glaciers retreat.”

Read more about the relationship between methane and glacier retreat here.

Methane-oxidizing Bacteria Methylosinus Trichosporium (Source: Ezra Kulczycki/ PNAS)
Methane-oxidizing Bacteria Methylosinus Trichosporium (Source: Ezra Kulczycki/ PNAS).


Grazing Patterns in Glacier-fed Wetlands

In PLOS ONE, “Grazing areas management is of utmost importance in the Andean region. In these harsh mountains, unique and productive wetlands sustained by glacial water streams are of utmost importance for feeding cattle herds during the dry season. After the colonization by the Spanish, a shift in livestock species has been observed, with the introduction of exotic species such as cows and sheep, resulting in a different impact on pastures compared to native camelid species—llamas and alpacas. Our results suggest that the access to market influenced pastoralists to reshape their herd composition, by increasing the number of sheep. They also suggest that community size increased daily grazing time in pastures, therefore intensifying the grazing pressure.”

Explore the influence of glacier meltwater on wetland size and herd composition here.

Llama in a sea of sheep grazing in a farm (Source: Brianne Hughes/ Pinterest )
A llama in a sea of sheep grazing on a farm (Source: Brianne Hughes/ Pinterest).

Roundup: GLOFs, Iron, and Soil Stability

Roundup: GLOFs, Iron, and Soil


Observations of a GLOF near Mt. Everest

From The Cryosphere: “Glacier outburst floods with origins from Lhotse Glacier, located in the Everest region of Nepal, occurred on 25 May 2015 and 12 June 2016. The most recent event was witnessed by investigators, which provided unique insights into the magnitude, source, and triggering mechanism of the flood. The field assessment and satellite imagery analysis following the event revealed that most of the flood water was stored englacially and that the flood was likely triggered by dam failure.”

Read more about the GLOF events in Nepal here.

Image of a GLOF from the Lhotse Glacier in June 2016 (Source: Caroline Clasoni/Twitter).


Transfer of Iron to the Antarctic

From Nature: “Iron supplied by glacial weathering results in pronounced hotspots of biological production in an otherwise iron-limited Southern Ocean Ecosystem. However, glacial iron inputs are thought to be dominated by icebergs. Here we show that surface runoff from three island groups of the maritime Antarctic exports more filterable than icebergs. Glacier-fed streams also export more acid-soluble iron associated with suspended sediment than icebergs. Significant fluxes of filterable and sediment-derived iron are therefore likely to be delivered by runoff from the Antarctic continent. Although estuarine removal processes will greatly reduce their availability to coastal ecosystems, our results clearly indicate that riverine iron fluxes need to be accounted for as the volume of Antarctic melt increases in response to 21st century climate change.”
Learn more about iron transfer here.

Iron ore on an Antarctic glacier (Source: jpfitz/Twitter).


The Role of Vegetation in Alpine Soil Stability

From International Soil and Water Conservation Research: “One fifth of the world’s population is living in mountains or in their surrounding areas. This anthropogenic pressure continues to grow with the increasing number of settlements, especially in areas connected to touristic activities, such as the Italian Alps. The process of soil formation on high mountains is particularly slow and these soils are particularly vulnerable to soil degradation. In alpine regions, extreme meteorological events are increasingly frequent due to climate change, speeding up the process of soil degradation and increasing the number of severe erosion processes, shallow landslides and debris flows. Vegetation cover plays a crucial role in the stabilization of mountain soils thereby reducing the risk of natural hazards effecting downslope areas.”
Read more about soil stability here.

Vegetation on Mount Rainier (Source: National Park Service).

Explore the Homeland of the Emperor Penguin

Each winter, thousands of Emperor Penguins leave the ocean and start marching to a remote place in Antarctica for their breeding season. Blinded by blizzards and strong winds, only guided by their instincts, they march to an isolated region, that does not support life for most of the year…

March of the Penguins

The famous documentary March of the Penguins, directed by Luc Jacquet, earned the emperor penguin fanfare and admiration around the world. With their charismatic shape and loving nature, emperor penguins reside on the ice and in the ocean waters of Antarctica for the entirety of their lifespan, living on average from 15 to 20 years. 

Satellite data has been used to help researchers better understand emperor penguin populations and how they respond to environmental variability, including the threat of a rapidly warming planet. But the information gleaned so far remains too limited to significantly help conservation efforts. Enter André Ancel, a researcher who led a team on a mission to study the remaining areas where emperor penguins might breed. His team recently published their findings in the journal Global Ecology and Conservation.

March of the Penguins Official Trailer:


Photos of emperor penguins taken close to Dumont d’Urville station (source: André Ancel).
Photos of emperor penguins taken close to Dumont d’Urville station (source: André Ancel).
“The climate of our planet is undergoing regional and global changes, which are driving shifts in the distribution and phenology of many plants and animals,” Ancel writes in his paper. “We focus on the southern polar region, which includes one of the most rapidly warming areas of the planet. Among birds adapted to live in this extreme and variable environment, penguin species are the best known.”

Even with their extreme adaption capabilities, emperor penguin breeding colonies are impacted by the fact that chicks often succumb to Antarctic elements. “Though they are one of the tallest and heaviest birds in the world, the survival rate of newborn emperor penguins is really low, only about 19 percent,” Shun Kuwashima, a PhD student at UCSC and self-declared penguin lover, explained. The purpose of Ansel et al.’s research was to predict how the species responds to climate change and to better understand the penguins’ biogeography, or geographical distribution.

“There are only about 54 known breeding colonies,” notes Ancel, “many of which have not yet been comprehensively studied.”

Location of the 54 emperor penguin breeding colonies around the Antarctic continent (source: Ancel et al.).
Location of the 54 emperor penguin breeding colonies around the Antarctic continent (source: Ancel et al.).
But finishing the research was a problem, considering that access to emperor penguin colonies remains limited. Getting accurate measurements on the size and location of the colonies relies on ground mapping and aerial photographs, which is “laborious, time consuming and costly,” according to Ancel. Even with the help of satellites, heavy cloud cover in the winter degrades the quality of images. Not to mention, the lack of light further complicates the collection of accurate data. In addition, the break-out of sea ice at the end of the breeding season can reduce the probability of detecting breeding colonies.

Although the authors did not actually conduct any exploration or examine remote sensing data to locate new emperor penguin colonies, they used data on the location of known colonies to make their findings. Based on the behavioral patterns of penguins, including movement and dispersal, and on the availability of food, the researchers found “six regions potentially sheltering colonies of emperor penguins.”

“What a big ship” (source: Arctic Al / Flickr).
“What a big ship!” (source: Arctic Al /Flickr).
It is true that scientists have looked for emperor penguin colonies with satellite data in the past, but the method was limited. To make improvements and find potentially missing colonies, the team developed an approach for calculating separation distance between colonies.

The approach determined the loxodromic separation distance (the shortest distance between two points on the surface of a sphere) between each pair of geographically adjacent colonies. Then, based on the fact that a breeding adult can travel 100 km from the colony during the breeding period, assuming a circumpolar distribution, the researchers pinpointed the potential areas where emperor penguin colonies might exist or could settle.

Emperor penguins with a chick (source: André Ancel).
An emperor penguin with a chick (source: André Ancel).
“Based on distances between existing colonies, we found six regions potentially sheltering colonies of emperor penguins,” Ancel explained to GlacierHub. “Some of the regions are located near glaciers.”

The regions identified by Ancel et al. do not fundamentally differ from the areas of other known colonies, which makes it possible that there are more than 54 colonies. It is similarly plausible that emperor penguins are adapting to new conditions through behavioral changes, Ancel indicated.

Safe harbor for an emperor penguin chick (source: Ignacio Nazal / Flickr).
Safe harbor for an emperor penguin chick (source: Ignacio Nazal/Flickr).
He expressed anxiety about climate change, noting that emperor penguins do not appear to show much flexibility in this regard. Emperor penguins live on sea ice off the coast, with some living near glaciers, including by Taylor Glacier, Mertz Glacier and Dibble Glacier. They require a proper amount of ice: not too much, so they can walk to the sea and hunt for food, but also not too little, so they can stay away from predators.

“Emperor penguins, like many other sea animals, are critically influenced by the harmful effects of global warming,” Kuwashima told GlacierHub in a recent interview. “The entire emperor penguin population could decrease by a third by the end of the century due to the inadvertent effect of climate change.”

It is heartbreaking to imagine that we may no longer be able to see the adorable emperor penguin chicks in Antarctica, but emperor penguins are in danger. As research conducted by Trathan et al. in 2011 showed, “In the Antarctic Peninsula region, one of the most rapidly warming parts of the planet during the latter part of the 20th century, one emperor colony has disappeared.”

Emperor penguin chicks at play (source: Ian Duffy / Flickr).
Emperor penguin chicks at play (source: Ian Duffy/Flickr).
Ancel concluded, “Our analysis highlights a fundamental requirement, that in order to predict how species might respond to regional climate change, we must better understand their biogeography and the factors that lead to their occupation of particular sites.” Armed with this knowledge, we might still be able to protect this beautiful species.

Photo Friday: Antarctic Glaciers Monitored by NASA

As the world’s fifth largest continent, Antarctica provides a unique record of the Earth’s past climate through its geomorphological record of glacier moraines. Antarctic glaciers terminate on land or in the sea as either floating ice shelves or grounded or floating outlet glaciers. As such, numerous climate scientists are conducting research about the ice shelf and glacier landforms in the southernmost continent to detect melting.

Specifically, a group of scientists with NASA’s Operation IceBridge mission have been doing field research over the Getz Ice Shelf in West Antarctica to collect data to monitor changes in polar ice and glaciers. The leading scientist, Nathan Kurtz, believes that Getz and glaciers in Antarctica are experiencing some of the highest basal melt rates in the world.

Take a look at some photos that demonstrate glacial melt in West Antarctica:

Getz crevasses (Source: Jeremy Harbeck/NASA)
Getz crevasses (Source: Jeremy Harbeck/NASA).


Evidence of a break along the front edge of Getz Ice Shelf, Antartica (Source: Margie Turrin/Columbia University's Lamont-Doherty Earth Observatory).
Evidence of a break along the front edge of Getz Ice Shelf, Antartica (Source: Margie Turrin/Columbia University’s Lamont-Doherty Earth Observatory).


Glaciers on mountains in Marie Byrd Land above Getz Ice Shelf (source:NASA)
Glaciers on mountains in Marie Byrd Land above Getz Ice Shelf (Source: NASA).


Tidewater glacier on Antarctic coast (source: Jason Auch/Flickr)
A tidewater glacier on the Antarctic coast (Source: Jason Auch/Creative Commons).


Jean de Pomereu (French, b. 1969), Fissure 2 (Antarctica) from Sans Nom, 2008, archival inkjet print, 107 x 129 cm, Whatcom Museum, Gift of the artist
A large crack leading to an Antarctica glacier (Source: Jean de Pomereu/Creative Commons).