Dispatch From the Cryosphere: Amid the Glaciers of Antarctica and Chile

As my year of research on glacier dynamics and water security in Chile came to a close in December 2018, I started searching for ways to put my newfound knowledge to good use while also soaking up the Patagonian summer. Through a bit of finesse and luck, I found a glacier education and guiding position for a polar expedition cruise company called One Ocean Expeditions. I felt like I was walking in a dream as I boarded an ice class cruise ship departing from Ushuaia, Argentina.

Through the five trips I worked on earlier this year, I had the great fortune to visit and interpret a myriad of glaciers from the shallow coves of the Antarctic Peninsula to the deep labyrinth of the Chilean fjords. Each glacier told a unique story, but a common theme emerged that links them all. While these massive, flowing systems may humble us with their power and enormity, they are deeply sensitive to their surroundings and profoundly affected by human-induced climate change.

There were four sites in my travels from the Antarctic Circle (66°33’S) north to Santiago, Chile (33°25’S) that best illustrated this duality for me.

Wilkinson and Murphy Glaciers, Crystal Sound, Antarctica

The sun peaked over the horizon as we crossed into the Antarctic Circle and washed an orange light over the endless whiteness of the Stefan Ice Piedmont and Wilkinson and Murphy Glaciers. I couldn’t ask for a more majestic first glimpse of Antarctica.

Stefan is a modest size for an ice piedmont, a term to describe a low-lying expanse of ice that gradually slopes from the edge of a mountain to the sea. In comparison, the Wilkinson and Murphy Glacier complex is quite large, serving as an outlet for the Antarctic Peninsula Ice Shelf through a network of multiple glacial valleys that converge to tumble down to the sea.

We waded through a bay of asymmetrical, peculiar icebergs that rivaled the size of our eight-story ship. Unlike the more uniformed, tabular icebergs we later encountered, which had neatly separated from ice shelves, these icebergs likely calved off Wilkinson and Murphy or a neighboring tidewater glacier.

A view of the Wilkinson and Murphy Glaciers in Antarctica (Source: Kate Cullen)
Icebergs adrift near the Wilkinson and Murphy Glaciers in Antarctica (Source: Kate Cullen)

Crystal Sound set the stage for Antarctica as a dreamy, vast-beyond-comprehension, and complex continent of ice—a place that feels other-worldly until you realize these calving glaciers and massive melting icebergs feed the same ocean we all share.  

Avalanche and Astudillo Glaciers, Paradise Harbor, Antarctica

Moving north, Paradise Harbor proved to be my favorite stop on each trip. It offers the best of the Antarctic Peninsula in mid-summer—calm and beautiful scenery, feeding humpback whales, porpoising penguins, and playful seals. We would start the day with a hike from the Almirante Brown Argentine base to a gentoo penguin colony and up to a bluff with a sweeping view of the massive Avalanche and Astudillo Glaciers.

Avalanche Glacier offers a prime location for observing Antarctic wildlife. (Source: Kate Cullen)

One of my colleagues commented that in the seven years she has visited Paradise Harbor, she’s witnessed Astudillo Glacier recede noticeably. I’m yet to find an up-to-date study that could corroborate or rebut this observation, but it would be consistent with the behavior of the glacier in the late 20th century—displaying a frontal recession from 1973 to 1989 to the LIMA observations in the early 2000s.

A view of the Avalanche Glacier (Source: Kate Cullen)

Astudillo isn’t an isolated case. We know that in the second half of the 20th century, 87 percent of glaciers on the Antarctic Peninsula were in a state of retreat. This widespread trend of melting, as well as rapid temperature increases and the collapse of two major ice shelves, has made the Antarctic Peninsula one of the many ground zeros of climate change.

While our days were tranquil, I wondered what the collapse of the Larsen B Ice Shelf, just over the ridge, felt like here and what the break-up of the even larger Larsen C Ice Shelf will bring.

Serrano Glacier, Cordillera Darwin Ice Field, Chile

Although they were connected until about 40 million years ago, the Antarctic Peninsula and southern tip of South America today feel like two separate worlds. The hardy, dwarfed vegetation of the Cordillera Darwin is a wash of green in comparison to the Antarctic landscape, and the glaciers are smaller, more active, and radiate a rich blue hue.

Serrano is a northern-facing glacier deep in the Agostini Fjord and outlet for the Cordillera Darwin Ice Field, the third largest expanse of ice in South America. On a sunny and wind-free morning, we maneuvered closer to Serrano’s face and marveled at a thick medial moraine that traced up to the convergence of two upper branches of the glacier.

The Serrano Glacier, Chile (Source: Kate Cullen)

The Serrano Glacier, like the vast majority of glaciers in the region, is losing mass. Between 2000 and 2011, its area thinned at an average rate of about 1.0±0.4 meters of water equivalent per year and, overall, the Ice Field lost an average of -3.9±1.5 gigatons of ice per year.

What struck me about Serrano is how gorgeous, massive, and storied it is, while remaining practically anonymous—located in a region that few have even heard of, Serrano is rarely visited or studied.  

Pío XI Glacier, Southern Patagonia Ice Field, Chile

In contrast, Pío XI, also known as Brüggen Glacier, is one of the most famous glaciers in South America. At a whooping 1,300 square kilometers, it is about as large as Los Angeles and is the biggest glacier on the continent—and one of the only that is advancing.

Between 1945 and 1995, Pío XI advanced 10 kilometers at speeds of up to 50 meters per day, paving over 400-year-old trees and sealing off the upper section of the fjord, which brought about the formation of a lake. It has since slowed considerably, as warmer temperatures have caused more precipitation to fall as rain instead of snow and its primary flow path has shifted from the south terminus to the north.

Scientists surmise that Pío XI surged, while its neighbors continued retreating, possibly because of high snow accumulation in its abnormally large basin, fjord-glacier interactions, elevated water pressure beneath the glacier, changes in geothermal activity, or sediment build-up at its terminus.

Chile’s Pío XI Glacier spans an area about as large as that of Los Angeles. (Source: Kate Cullen)

Such a famous and peculiar glacier, I could barely contain my excitement as we cruised into Eyre Fjord and watched the gargantuan, blue mass come into focus from the upper deck. I trailed behind Australian glaciologist Ian Goodwin with his black beret and sharp goatee as we walked along Pío XI’s wide southern terminal moraine and searched for the source of a sediment-rich stream gushing out from the bottom of the glacier.

Pío XI was unlike any other glacier we’d seen—the water was saturated with sediment and free of icebergs, the face was a modest height and sloped away from us, and we observed no calving events that day. The preposterous amount of sediment and continuous purge of meltwater begged a closer look. We scribbled notes and took pictures to report back to colleagues and pondered how we could return with a scientific purpose.  

A cryosphere in crisis

The recent headlines in Greenland remind us the cryosphere is changing faster than we can grasp. Our modeling and monitoring is more accurate than ever, but the general public is just beginning to understand the complexity and urgency of the issue.

I found that these cruises offered a powerful platform to connect with folks from across the political spectrum through an immersive and emotional crash course in glaciology. I’m not yet sure how, but there must be a way we can create equally moving but more accessible and sustainable educational opportunities. As I reflect comfortably at home, Wilkinson and Murphy, Avalanche and Astudillo, Serrano, and Pío XI continue to flow.

Read More on GlacierHub:

Dispatch from the Cryosphere: Glacier Decrease in the Georgian Caucasus

South Asian Perspectives on News of Rapid Himalayan Glacier Melt

Ancient Humans of Glaciated Western China Consumed High-Potency Cannabis

Roundup: Antarctic Coral, Laser Ultrasound, and Totten Glacier

Ecology of Antarctic Coral

From Science Direct: “Antarctic ecosystems present highly marked seasonal patterns in energy input, which in turn determines the biology and ecology of marine invertebrate species. The pennatulid Malacobelemnon daytoni, is one of the most abundant species in Potter Cove, Antarctica. Its biochemical compositions were studied over a year-round period. The profiles suggest an omnivorous diet and opportunistic feeding strategy for the species, which supports the hypothesis that resuspension events may be an important source of energy, reducing the seasonality of food depletion periods in winter. This gives us a better insight into the species’ success in Potter Cove and under the current environmental changes experienced by the Antarctic Peninsula.”

Learn more about the Malacobelemnon daytoni here.

The Antarctic Peninsula (Source: Halley Wombat/Creative Commons).
 

New Laser Ultrasound Aids Ice Core Studies

From MDPI: “The study of climate records in ice cores requires an accurate determination of annual layering within the cores in order to establish a depth-age relationship. We present a complimentary elastic wave remote sensing method based on laser ultrasonics, which is used to measure variations in ultrasonic wave arrival times and velocity along the core with millimeter resolution. Custom optical windows allow the source and receiver lasers to be located outside the cold room, while the core is scanned by moving it with a computer-controlled stage. These new data may be used to infer stratigraphic layers from elastic parameter variations within an ice core, as well as analyze ice crystal fabrics.”

Read more about the wave remote sensing method here.

Research teams in Antarctica to study lead pollution through ice cores (Source: NASA Goddard Space Flight Center/Creative Commons).
 

Totten Glacier Mass Loss

From University of Exeter: “A large volume of the East Antarctic Ice Sheet drains through the Totten Glacier (TG) and is thought to be a potential source of substantial global sea level rise over the coming centuries. We show the surface velocity and height of the floating part of TG, which buttresses the grounded component, have varied substantially over two decades, with variations in surface height strongly anti-correlated with simulated basal melt rates. Coupled glacier/ice-shelf simulations confirm ice flow and thickness respond to both basal melting of the ice shelf and grounding on bed obstacles. We conclude the observed variability of TG is primarily ocean-driven. Ocean warming in this region will lead to enhanced ice-sheet dynamism and loss of upstream grounded ice.”

Learn more about the Totten glacier’s mass loss here.

Shelf ice calving in Antarctica (Source: Ice Sheets/Wikimedia Commons).

Life on the Rocks: Climate Change and Antarctic Biodiversity

By now, it’s a familiar story: climate change is melting glaciers in Antarctica, revealing an increasing proportion of ice-free terrain. The consequences of this melt are manifold, and one may be surprising: as more ground is bared, Antarctic biodiversity is expected to increase.

Currently, most of the terrestrial biodiversity— microbes, invertebrates, and plants like grasses and mosses— occurs in the less than one percent of continental Antarctica that is free of ice. A recent Nature article predicted that by the end of the 21st century, ice-free areas could grow by over 17,000 square kilometers, a 25 percent increase.

Members of the shrinking Torgersen Island Adélie colony (Source: Rachel Kaplan).

This change will produce both winners and losers in Antarctica’s ecosystems, according to Jasmine Lee, lead author on the above paper, and the game will be problematic. “Some of the winners are likely to be invasive species, and increasing invasive species could negatively impact the native species,” Lee told GlacierHub. “More isn’t necessarily better if new species are alien species.”

The Antarctic Peninsula, an 800-mile projection of Antarctica that extends towards South America,  is one of the fastest-warming places on Earth, and 80 percent of its area is covered by ice. The many outlet glaciers of the Antarctic Peninsula Ice Sheet primarily shrink through surface melting, which reduces volume, while tidal action spurs calving. Lee and her coauthors constructed two models based on two Intergovernmental Panel on Climate Change (IPCC) climate forcing scenarios. Under the strongest IPCC scenario, ice-free areas in the peninsula are expected to increase threefold, and Lee expects biodiversity changes in this region to be obvious by the year 2100. She predicts that some native species will expand their ranges south in response to the creation of new habitat and milder conditions, and invasive species will thrive for the same reasons.

This pattern is already apparent in the distribution of a number of penguin species. As climate warms, sea ice-obligate species like Adélie and Emperor penguin are shifting and contracting their ranges southward, seeking sea ice. Likewise, ice-intolerant gentoo and chinstrap penguins, typical of the Subantarctic latitudes, are moving south as the ocean becomes increasingly free of ice. As temperatures continue to rise, this biogeographic chess will play out increasingly across Antarctica.

Glaciers in the Antarctic Peninsula converge into one calving front (Source: NASA ICE/ Flickr).

“The greater the degree of climate change, the greater the biodiversity impacts,” predicted Lee. She added that counting an Adélie colony in a “real-life ice-free area” was a highlight of her fieldwork.

Interestingly, Lee and her coauthors found that higher biodiversity in the short-term may yield greater homogeneity in the long-term, as invasive species become established and potentially out-compete native species. It’s hard to know how to feel about these ecosystem-wide transitions, said Lee. “The fact that we are driving these changes through anthropogenic climate change should remind us that our actions impact the entire earth, even in what we consider the remotest and most pristine regions. I think we should feel accountable and know that because humans have the power to change the earth, we should do our best to look after it,” she said.

Curious Adélie penguins assess Lee on Siple Island (Source: Jasmine Lee/Twitter).

On June 1, President Donald Trump made a speech announcing the United States’ exit from the Paris climate agreement, obfuscating international cooperation on climate change mitigation. Lee feels this decision sends the wrong message to the rest of the world, but she hopes that the United States will find a way to continue meeting the environmental standards set forth. “America should be a leader in renewable energy technology and policy. However, I am also hopeful that the American businesses and states can reach the Paris accord milestones for America in spite of Trump. And this will show that every city, state or business can have a positive impact regardless of governance,” she said.

No matter the ebb and flow of the political tide, the Antarctic Peninsula is changing. As Antarctic glaciers melt and biodiversity changes, mitigation will require the cooperative efforts of the world.

Roundup: Alpine Streams, Divergence and Ocean Acidification

Roundup: Streams, Oceans and Tiny Flies

Climate Change and Alpine Stream Biology

From Biological Reviews: “In alpine regions worldwide, climate change is dramatically altering ecosystems and affecting biodiversity in many ways. For streams, receding alpine glaciers and snowfields, paired with altered precipitation regimes, are driving shifts in hydrology, species distributions, basal resources, and threatening the very existence of some habitats and biota. Alpine streams harbour substantial species and genetic diversity due to significant habitat insularity and environmental heterogeneity. Climate change is expected to affect alpine stream biodiversity across many levels of biological resolution from micro- to macroscopic organisms and genes to communities.”

Learn more about alpine stream biology here.

An alpine stream in Banff Canada (Source: Bernard Spragg/Flickr).
An alpine stream in Banff, Canada (Source: Bernard Spragg/Flickr).

 

Ecological Divergence of the Alpine Mayfly

From Molecular Ecology: “Understanding ecological divergence of morphologically similar but genetically distinct species – previously considered as a single morphospecies – is of key importance in evolutionary ecology and conservation biology. Despite their morphological similarity, cryptic species may have evolved distinct adaptations. If such ecological divergence is unaccounted for, any predictions about their responses to environmental change and biodiversity loss may be biased. We used spatio-temporally replicated field surveys of larval cohort structure and population genetic analyses (using nuclear microsatellite markers) to test for life-history divergence between two cryptic lineages of the alpine mayfly Baetis alpinus in the Swiss Alps… Our results indicate partial temporal segregation in reproductive periods between these lineages, potentially facilitating local coexistence and reproductive isolation. Taken together, our findings emphasize the need for a taxonomic revision: widespread and apparently generalist morphospecies can hide cryptic lineages with much narrower ecological niches and distribution ranges.”

Read more about ecological divergence here.

A common species of mayfly (Source: Luc Viatour/Creative Commons).
A common species of mayfly (Source: Luc Viatour/Creative Commons).

Ocean Acidification in the Antarctic Coastal Zone

From ScienceDirect: “The polar oceans are particularly vulnerable to ocean acidification; the lowering of seawater pH and carbonate mineral saturation states due to uptake of atmospheric carbon dioxide (CO2). High spatial variability in surface water pH and saturation states (Ω) for two biologically-important calcium carbonate minerals calcite and aragonite was observed in Ryder Bay, in the coastal sea-ice zone of the West Antarctic Peninsula. Glacial meltwater and melting sea ice stratified the water column and facilitated the development of large phytoplankton blooms and subsequent strong uptake of atmospheric CO2 of up to 55 mmol m-2 day-1 during austral summer. Concurrent high pH (8.48) and calcium carbonate mineral supersaturation (Ωaragonite ~3.1) occurred in the meltwater-influenced surface ocean… Spatially-resolved studies are essential to elucidate the natural variability in carbonate chemistry in order to better understand and predict carbon cycling and the response of marine organisms to future ocean acidification in the Antarctic coastal zone.”

Read more about ocean acidification here.

The majestic scenery of Antarctica (Source: Reeve Joliffe/Flickr).
The majestic scenery of Antarctica (Source: Reeve Joliffe/Flickr).

Ocean temperatures main cause of glacier melt in the Antarctic Peninsula

Along the 1,200 kilometer western coastline of the Antarctic Peninsula, hundreds of glaciers stretch down to the sea. Glacier melt from this region is a major contributor to global sea-level rise. While scientists have looked to rising atmospheric temperatures to explain the rapid glacier melting in recent decades, a new study reveals that ocean temperatures may actually be the main cause of glacier retreat in the region.

Aerial photo of the Antarctic Peninsula (Source: Wild Frontiers)
Aerial photo of the Antarctic Peninsula (Source: Wild Frontiers)

The Antarctic Peninsula is in the northernmost part of the continent, and lies 1,000 kilometers from the tip of South America. Due to its latitude between 63 and 70 degrees South, the peninsula has the most moderate climate and — relatively speaking — warmest temperatures in Antarctica. As a result, glacier retreat in this area occurs at a faster rate than in most of the rest of the continent. However, melting has accelerated in recent years, raising concern in the scientific community. The atmospheric temperature record over the past several decades shows warming in the region. Rising atmospheric temperatures have, until now, been considered the largest contributing factor to glacier melting on the peninsula.

Satellite image of the Antarctic Peninsula (Source: Dave Pape/Anna Frodesiak)
Satellite image of the Antarctic Peninsula (Source: Dave Pape/Anna Frodesiak)

This study, published in Science on July 15, offers a new explanation in its surprising finding that ocean temperatures correlate more closely to glacier melt than air temperatures. The team, led by Alison Cook of Swansea University in the United Kingdom, investigated the relationship between ocean temperatures and glacier retreat in response to research, which showed that the air temperature record in the Antarctic Peninsula did not correctly predict the timing or location of glacier melt in the region.

Along the Antarctic Peninsula, there has been more ice loss in the colder southern end of the peninsula than in the warmer north. Air temperatures fail to explain this dramatic gradient along the peninsula, leading the team to seek another explanation. Using detailed data from the World Ocean Database, the researchers were able to track ocean temperatures along the Antarctic Peninsula between 1945 and 2009. When this data was compared to observed glacier retreat over time, a strong connection was revealed.

In the southern portion of the Antarctic Peninsula, mid-depth ocean temperatures were higher than in the north. By dividing the ocean near the peninsula into 6 study regions, the team of researchers from Swanea and British Antarctic Survey found that the ocean water composition was very different between the top and bottom half of the peninsula.

Along the southwestern coast of the peninsula, water from multiple oceans meets to form Circumpolar Deep Water (CDW). In this region, a mix of Antarctic, Pacific, and Atlantic water masses dominates the ocean composition. The temperature and salinity of the water along the southwestern coast is unique because of the mixing of different water sources — cold salty water sinks, while warmer water settles at mid-range depths. The CDW in the region has an average temperature of 4 degrees Celsius above the seawater freezing point.

Diagram illustrating how Circumpolar Deep Water flows onto the continental shelf and drives high melt rates at the grounding line of glaciers (British Antarctic Survey)
Diagram illustrating how Circumpolar Deep Water flows onto the continental shelf and drives high melt rates at the grounding line of glaciers (Source: British Antarctic Survey)

However, Shelf Water and Bransfield Strait Water surround the northern portion of the peninsula. These waters are only 1 and 2 degrees above seawater freezing point, respectively. The warmer southern waters correspond to the areas of the peninsula that have had the most glacier melt, and explain why the southern peninsula has more ice loss than the northern area.

While it may seem that the surface temperature of the water would be the most important factor affecting glacier melt, the team found that it is actually the temperature of water 100 to 300 meters below the surface that correlates strongest with glacier melt — the bottom of the glaciers extending off the coastline fall within this range, and the warm water melts them from below the surface.

When fresh, cold water melts from the glaciers into the ocean, it causes upwelling — a process in which deep water rises to the surface. When warm Circumpolar Deep Water upwells onto the ice shelf, it accelerates the rate of glacier melt. In the north, where the deep water is still cold, this phenomenon does not occur.

The results show that warm ocean water is causing glacier retreat in a staggering 90 percent of the 674 glaciers that drain into the ocean. This important finding in the western Antarctic Peninsula means that conservation strategies need to be reconsidered and climate models readjusted, according to the authors. In order to accurately predict global environmental changes including sea-level rise, the temperature of coastal ocean water needs to be included as not only a factor, but the main factor in glacier melt.