CR
Cryospheric Sciences

Antarctica

Cryo-Comm – Capturing Ice

Cryo-Comm – Capturing Ice

In this week’s blogpost, author, editor, artist, and outreach expert Marlo Garnsworthy gives some insights into her recent trip to Iceberg Alley, gives you some tips on how to communicate icy science, and shows us her inspirational artwork.


If you’re reading this, ice may be on your mind. Ice is surely on mine.

During my day job as a creative and editor, I dip frequently into Twitter for the latest cryosphere news. Memories of the Antarctic rumble like the thrusters of the research vessels I’ve called home: constant, comforting, and rising to a roar when I need stabilizing. Thoughts of polar science keep me steady and on course.

You may think scientists and creatives are very different. In fact, in the creative world, as in science, success comes with years spent developing wide-ranging technical and communication skills, less-than-stellar pay, so many rejections, and hard-won moments of joy. Both worlds require resiliency, a good attitude, and stamina. Incidentally, these experiences forge the soft skills we need for remote expeditions—we’re tough, don’t sweat the small stuff, and play nicely.

 

Going South

I first went south in 2017. I was invited by paleoceanographer Rebecca Robinson to sail on SNOWBIRDS Transect, studying diatoms and diatomaceous ooze, from McMurdo Station through the Southern Ocean. Seeing polar ice—from great grinding glaciers through the window of our Hercules LC-130, to the mosaic of melting summer sea ice in the Ross Sea, to massive icebergs drifting by—was transformative. I was in love with polar ice and with my Outreach role. I had to return.

So, I painted a LOT of polar scenes. I networked via social media and APECS workshops. I learned all I could about ice. I teamed up with my brilliant collaborator Kevin Pluck to form PixelMoversAndMakers.com.

 

And it all paid off.

I was invited to sail as Onboard Outreach Officer on the JOIDES Resolution, a drilling ship for the International Ocean Drilling Program. Expedition 382—Iceberg Alley took us to the iceberg-strewn Scotia Sea, where we cored millions of years of sediment. It will allow our team, led by Mike Weber and Maureen Raymo, to reconstruct past melting of the Antarctic Ice Sheet.

Of course, melting.

As I’ve gained more intimate knowledge of what is happening to our polar ice, making lasting changes to how I live has become my only moral choice. Not doing all I can to inform others has become unconscionable. I continue my work to connect a wide audience to the beauty and plight of our polar ice, always hoping I will return. Yet equally important to me is helping polar researchers better communicate their work.

 

Bringing the Poles to the People

We’re lucky that our science involves places of breathtaking beauty and harshness that most can only dream of seeing in person. It’s not difficult to engage people in the adventure. But conveying polar science comes with unique challenges because the subject of our work is so remote.

As an artist, I think, how can I show the subtle shifts in color, contrast, and texture of icy landscapes? The swiftly changing light, the sudden snow squalls, and the roaring of wind and waves—in a still image? The expanse of space and time in something that will fit on page or screen?

As a storyteller, how do I describe the sounds of a ship’s hull as it breaks sea ice? How it feels to live for months on a heaving surface? The thrill as icebergs pass by our vulnerable ship? The delight of breaching humpbacks and circling penguins? The boredom of eating cabbage at every meal? The bonds that form and the emotional costs of being far from home for months?

As a science communicator, I think, what do I want to say? What do I need to convey? Who is my audience? How do I show our scientific objectives in terms they can understand? How do I make grueling hours of lab- and fieldwork exciting and accessible? How can I most effectively use social media? How can I best speak to a crowd? How can I expand our audience?

Above all, how can I show why it all matters?

The public is becoming more aware of polar melting. But there’s a gaping crevasse between hearing something and really internalizing it. There’s a gulf between knowledge and action. Such leaps in consciousness and behavior can happen suddenly like an iceberg calving; more often, they happen as gradually as a glacier flows.

Ice shelf, ocean and sky [Credit: Marlo Garnsworthy].

Telling a Story

Ultimately, it boils down to this: What can we make people feel? I believe effective science emotion turns facts (data) into “truth” (emotion) and that storytelling is our most powerful tool.

All good stories have a beginning, a middle, a climax, and a resolution. When I tell polar stories, I often aim to take people on this journey:

Beginning: Excitement & Wonder

Come on a faraway adventure: Glaciers! Icebergs! Vast icy vistas! Wild storms and massive seas… PENGUINS!

Middle: Interest & Awe

Whoa. That’s a WHOLE lot of ice. Here’s how we study it. Here’s why we study it.

Climax: Anxiety

Here’s how it feels. Yes, it’s melting. It might be far away, but it’s coming to a coastline near you…

Resolution: Hope & Motivation

But it’s not too late. There’s something we can do. Let’s get going! And…

PENGUINS!!!

(Always remember to include humor.)

What story will you tell?

 

Ice & Fire

On Wednesday 25th of September, the IPCC Special Report on the Ocean & Cryosphere in a Changing Climate (SROCC) was released. It’s unlikely to leave us feeling warm and fuzzy. But please let it fire up your passion to creatively share your science.

What skills can you offer? Do you enjoy photography? Making videos? Can you write a funny limerick or poignant haiku? Are you skilled with numbers or writing code? Are you good at building structures? At telling a story? At playing a musical instrument? At organizing things or people? Are you a social media whiz? (If not, it’s time to become one.) Your unique skills, whatever they may be, are waiting to be harnessed for creative sci-comm.

Speak simply. Speak the truth. Above all, speak your truth. Don’t be afraid to let your emotional connection to your work and polar regions show. And amplify others’ Outreach efforts, too. Together, we’re on the vanguard of this battle for awareness and action.

The interesting life found within the Antarctic inspires some of Marlo’s artwork [Credit: Marlo Garnsworthy].

Further links

  • SNOWBIRDS Transect website
  • Pixel Movers and Makers website
  • Iceberg of Antarctica book (free download)
  • Iceberg Alley and Subantarctic Ice and Ocean Dynamics project website
  • Marlo’s website

Edited by Jenny Turton


Marlo Garnsworthy is the author/illustrator of “Iceberg of Antarctica” (available as a free download) and several other books and is seeking her next polar adventure. Find her at www.WordyBirdStudio.com and PixelMoversAndMakers.com (with Kevin Pluck). Marlo tweets from @MarloWordyBird.

Image of the Week – Unravelling the mystery of the 2017 Weddell Polynya

Figure 1: The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite acquired these images of the Maud Rise or Weddell polynya in the eastern Weddell Sea on September 25, 2017. The first image is natural color and the second is false color where areas of ice are in blue and clouds are in white. [Image credit: NASA Earth Observatory].

The mysterious appearance and disappearance of the Weddell Polynya, a giant hole in the ice, has long puzzled scientists. Recent work reveals that it is tightly tied to energetic storms. Read on to find out more…


The eastern side of the Weddell Sea is a region known for its low concentration of sea ice due to the presence of a seamount, an underwater plateau called the Maud Rise. The seamount influences ocean circulation by bringing warm water closer to the surface, preventing the formation of thick ice. In the early 1970s, when satellites first began snapping photos of Earth, scientists noticed a mysterious hole in Antarctica’s seasonal sea ice floating in this area. This phenomenon is known as a polynya, and for decades its occurrence went unexplained. Then in 2017, during the continent’s coldest winter months, when ice should be at its thickest, a giant 9,500-square-kilometre hole suddenly showed up in the same region (Figure 1). Two months later it had grown 740% larger, before merging with the open ocean at the beginning of the melt season.

The Weddell Polynya is a rather famous hole in the ice (see this previous post). Scientists have been investigating such features in the Southern Ocean for decades, but the true reasons for the appearance and disappearance of the Weddell Polynya were still surrounded by mystery – until now.

Why does the Weddell Polynya form?

Recently, our new study found that these mid-sea polynyas can be triggered by strong cyclonic storms. Using satellite observations and reanalysis data, we found that in some winters, atmospheric circulation moves a significant amount of heat and moisture from mid-latitudes to Antarctica, allowing large cyclones to develop over the sea ice pack. When strong cyclones – some as strong as hurricanes – form and spin over the ice pack, the strong cyclonic winds they can drag the floating sea ice in opposite directions away from the cyclone center, creating the opening.

Sea ice typically drifts in a direction turned 30° on average to the left of the atmospheric flow, with a speed amounting to 1–2% of the surface wind speed. Those rules, when applied to a cyclonic wind situation (i.e., two opposing winds around a center), imply divergence in the motion of sea ice leading to open water area within the cyclone center, as in Fig. 2. We can see how such a situation occurs in real life for the Weddell Polynya when looking at Fig. 3, where near-surface winds exceeding 20 m/s are pushing the ice in opposite directions away from the cyclone center, characterized by weak winds, and the hole in the ice underneath it.

Figure 2: Sketch summarizing the mechanisms by which the cyclone can open the polynya [Credit: Francis et al., 2019].

Why does the Weddell Polynya matter?

Once opened, the polynya works like a window through the sea ice, transferring huge amounts of energy during winter between the ocean and the atmosphere. Because of their large size, mid-sea polynyas are capable of impacting the climate regionally and globally. This includes impact on the regional atmospheric circulation, the global overturning circulation, Antarctic deep and bottom water properties, and oceanic carbon uptake. It is important for us to identify the triggers for their occurrence to improve their representation in models and their effects on climate.

What might happen in the future?

Under future warming-climate conditions, previous studies have predicted an intensification of the activity of polar cyclones and a poleward shift of the extratropical storm track. Others have shown that a poleward shift of the cyclone activity can result in a reduced sea ice extent, a situation similar to that observed in 2016 and 2017. When the sea ice extent is reduced, preferable polynya areas (i.e. areas of thinner ice, for example the Maud Rise) located in the ice pack become closer to the ice edge and hence to the cyclogenesis zone. Given the link between polynya occurrence and cyclones, polynya events may thus become more frequent under a warmer climate.

Figure 3 AMSR2‐derived sea ice concentrations on 16 September 2017 at 1200 UTC (colors) and ERA5 10‐m winds less than 20 m/s in black contours, and greater than 20 m/s in red contours.The solid yellow contour is the 15% ERA‐Interim sea ice contour, the dotted yellow contour is the 50% ERA‐Interim sea ice contour, and the dashed white contour is the 15% ice from satellite data delineating the polynya area. [Credit: Francis et al., 2019].

Further reading

Edited by Lettie Roach


Diana Francis is an atmospheric scientist at New York University Abu Dhabi, UAE. She investigates atmospheric dynamics in polar regions with focus on polar meteorology and links to changes in land and sea ice conditions. To this end, she uses regional models together with available observations and reanalyses. She tweets as @drdianafrancis.
Contact Email:  diana.francis@nyu.edu

Image of the Week – The Lost Meteorites of Antarctica…

Image of the Week – The Lost Meteorites of Antarctica…

 When most people think of Antarctica, meteorites aren’t the first things that come to mind. Perhaps they imagine the huge ice shelves, the desolate interior, or perhaps penguin colonies near one of the scientific bases — but usually not meteorites. So why is our project looking for meteorites in Antarctica, and besides, aren’t they all lost until they are found?


Let’s start with the Antarctic part. Surprisingly, Antarctica is a great place to hunt for meteorites, with two-thirds of all known meteorites found there (see also this previous post). Despite the difficult searching conditions, the dark meteorites show up well on the bright white surface of the ice sheet. Also, due to the cold conditions, the weathering of meteorites is slower than in warmer regions, such as hot deserts. However, Antarctica is vast and most meteorites are small (a few cm in size) so finding them is still difficult. One thing that helps in this case is the presence of mountain ranges and nunataks near the perimeter of the continent. These slow the ice flow and cause stagnation points — blue ice areas (see Fig.1) — where meteorites can collect and accumulate on the surface usually at elevations of 1500m to 2500m or so.

To understand the “lost” part, you need to know that not all meteorites are created equally – some are stony, somewhat like the rocks found in the Earth’s crust, whilst others are more metallic, having a high iron content perhaps close to 90%. The latter tell a meteoriticist (yep, this is a real job definition!) about the cores of planets and the early formation of the solar system. In the rest of the world these rarer and more interesting iron meteorites usually make up about 5.2% of all samples found — but on the ice sheet, they only represent about 0.6%, an order of magnitude less.

This under-representation is a little odd and unexpected. We don’t expect any particular bias due to delivery to Earth, and if you’re out hunting for meteorites on your skidoo and spot a dark rock that’s potentially a meteorite, you’re still going to pick it up: so no bias in collection.

So where are the missing iron meteorites?

About 3 years ago a team from Manchester were looking at this problem and came up with a hypothesis that might explain it: as sunlight enters the blue ice and gets scattered below the surface it gets absorbed by meteorites and heats them up. This happens more on their upper surface, and due to the higher conductivity of iron meteorites in comparison to their stony counterparts, the heat is transferred to the ice below. Given the right conditions during the Austral summer, this process can provide enough energy so that iron meteorites melt the ice underneath them and sink a few centimetres below the surface whilst the stony ones stay on top. Though we put this on a mathematical footing by way of a model and confirmed the mechanism by some laboratory experiments, the only way to be sure that there is a layer of iron meteorites hiding below the surface is to go out and find them.

Fig. 2: Meteorite close-up: partially embedded in the blue ice surface [Credit: Katherine Joy/Lost Meteorites of Antarctica].

The current project

If you’re going to try and find iron meteorites hidden below the ice surface in Antarctica, then you’re going to need a new way of doing things. Ordinarily, searches are carried out by systematically searching an area of blue ice on skidoo and looking for dark rocks that might be potential meteorites (see Fig. 2). Obviously this won’t work for samples below the surface, so we had to come up with a new method that allows a good sized area to be covered (even in a relatively productive area we estimate the density of irons is <1 km-2) and can cope with the conditions up on the Antarctic plateau. Given that the key discriminating characteristic of the subsurface meteorites is their metallic content, it makes sense to use a system based on metal detector technology.

Our system is somewhat different to what you might use for hunting for archaeological coins or have to walk through at the airport, and instead the detector coils are embedded into an array of large polymer panels (the same material the British Antarctic Survey use for transporting fuel drums on). It’s entirely bespoke, including the pulse and detection electronics, data acquisition and analysis, and importantly, it’s designed to be able to deal with the conditions we expect down South.

Fig 3: The prototype detection system being tested at Sky-Blu Field Station during the 2018/19 season. Panels are on the left of the image, control electronics are beneath the photovoltaic panel in the centre, and an indicator box on the skidoo shows when something metallic is detected [Credit: Geoff Evatt/Lost Meteorites of Antarctica].

Even so, given the logistical challenges of remote working in Antarctica (the area we want to search is ~700 km from the nearest base), we thought it prudent to do some tests of the prototype equipment closer to home. To that end, we’ve had two field trips to the UK Arctic Research Station in Ny Ålesund on Svalbard for the initial testing of the detection equipment.

In addition, we need to figure out exactly where to search. We therefore need to confirm an area has surface meteorites before we can hope to find the subsurface layer. That was the point of last Austral summer’s expeditions: while one team kept close to the Sky-Blu base for the first Antarctic test of full detector array, the other team went out to the Recovery Glacier region for a visual search of surface meteorites. Thankfully both were a success, with our meteorite hunting team bringing back a total of 36 surface meteorites.

Fig 4: The meteorite search team’s home for a few weeks. 700 km from Halley and poor weather meant return to civilisation was delayed until the Twin Otter could fly in [Credit: Katherine Joy/Lost Meteorites of Antarctica].

A bit more planning and we’re lined up for next year’s expedition where it all comes together and we find out if the hidden layer is there – or there’s something else at work…

You can find out more about the project and what we’re up to on the project blog: https://ukantarcticmeteorites.com/blog/

Further reading

Edited by Clara Burgard


Andy Smedley trained as an atmospheric scientist measuring and modelling how sunlight interacts with the atmosphere. Recently his research interests have expanded to include sunlight’s interaction with, and impacts on, the cryosphere. He is currently working on the Leverhulme Trust funded “Lost Meteorites of Antarctica” project at the University of Manchester where he deals with the logistics of Antarctic field expeditions, mapping and analysis to select the field sites, and trying to better understand how solar radiation interacts with blue ice and light absorbing particles – including meteorites.

Image of the Week – Who let the (sun)dogs out?

Figure 1a: Atmospheric formations on the interior Antarctic plateau near Dome Fuji. Photo credit: B. Van Liefferinge

How peaceful it is to contemplate the sky … This is especially true of polar northern or southern skies where the low temperatures can engender unique light phenomena. We often tend call them all, wrongly, sundogs, but in fact, many more phenomena exist. To list a few, you can observe a parhelic circle, a 22° halo, a pair of sun dogs, a lower tangent arc, a 46° halo, a circumzenithal arc, a parry arc, … This year, I had the chance to observe several of these phenomena during my fieldwork on the Antarctic plateau. I am no cloud specialist or meteorologist, but I would like to give you some explanations to better understand this sky art you might see one day.


Figure 1b: Atmospheric formations on the interior Antarctic plateau near Dome Fuji. Photo credit: B. Van Liefferinge

Everything starts with the ice crystals inside the clouds. Ice crystals can be approximated as hexagonal prisms, and two shapes can be found naturally: plates and columns (Fig.2), mainly dependent on air temperature and humidity. Clouds formed from these ice crystals are relatively thin and therefore sun rays can pass through them easily. In cold regions (polar or not), the ice crystals can also be found at ground level (in that case, they are called diamond dust).

Figure 2: atmospheric halos in the Antarctic plateau, 27 ‎November ‎2018. Plate crystal (left) and column crystal (right), modified from Walter Tape, 1994. Photo credit: B. Van Liefferinge

The observed light patterns in the sky are caused by the refraction of sun rays on the ice crystals. As they hit the crystals, the sun rays are diverted from their trajectory. Depending on the orientation of the crystals in the cloud, and the type of crystal present in the cloud, this will affect the sun ray paths differently. The resulting halos or arcs seen in the sky will result from the combination of all the different ray paths through all the clouds’ crystals together. The sun ray paths through the crystals can become quite complex, as illustrated in Fig. 3.

Figure 3: Example of a complex ray path through a plate crystal which contributes to forming a left parhelic circle (left), example of a complex ray path through a hexagonal crystal which contributed to forming a tricker arc (right), (Walter Tape, 1994). Photo credit: B. Van Liefferinge

As an example, let’s try to understand how the 22° halo forms (see Fig.1 a and b), one of the most common halos observed. The 22° halo is formed in clouds that have randomly oriented column crystals (although this is still under debate). When a sun ray hits an ice crystal, the most common path it will take is to refract through the face of the hexagon it hits (e.g. face 1 on Fig.4) and refract back out of a face opposite (face 3 on Fig.4). The angle between face 1 and face 3 is of 60°. A light ray passing through two faces of an ice crystal inclined at 60° from each other is deflected through angles from 22° up to 50°. The deflection at 22° is the most probable and therefore creates the brightest circle in the sky (the 22° halo!). The other deflections above 22° are less common but occur nonetheless and form the fade disk (Fig. 4). No light can be refracted through smaller angles then 22° (this is a result of the air-to-ice index of refraction). This is why you see a “darker sky” inside the halo. Now, add to this that we have been considering white light in general. But in fact, visible white light is composed of visible red through blue rays, which do not deviate by the same amount (21.54° for red light to 22.37° for blue light). This explains why the 22° halo looks like a rainbow.

Figure 4: Sun ray path through an ice crystal (left), resulting 22° halo (right) [Credit: B. Van Liefferinge].

Now let’s go back to our famous sundog. If you understood the 22° halo, it will be a piece of cloud! Sundogs follow the same rule as the 22° halo: sun rays passing through two ice crystal faces inclined at 60° to each other are deflected through a minimum angle of 22°. The difference here is that for a sundog to form, the ice crystals must all be aligned along the horizontal direction. This is the case when the ice crystals are all plate crystals (Fig.5), which, as a result of their shape, tend to align horizontally in clouds. As sun rays traverse them, they are deflected into two specific spots either side of the sun, instead of along a circle when crystals are randomly oriented (like for the 22° halo).

Figure 5: Sundog formation [Credit: Atmospheric Optics website]

And finally, I’ll let you enjoy a light show, filmed recently over Svalbard on a perfect day for atmospheric formations (video courtesy of Ashley Morris)…

 

A few more fun facts:

Edited by Marie Cavitte


Brice Van Liefferinge is a trained geographer, glaciologist and modeller. With a background in geography at the Université libre de Bruxelles (ULB, Belgium), he pursued his interest in Earth sciences during his PhD looking at the thermal regime of the Antarctic Ice Sheet and working on the Beyond Epica Oldest Ice project. He is now working on the Oldest Ice Dome Fuji project with Dr. Kenny Matsuoka at the Norwegian Polar Institute (NPI, Tromsø, Norway) for which he just came back from 3 months of fieldwork at Dome Fuji, Antarctica.

 

Image of the Week – Kicking the ice’s butt(ressing)

Risk map for Antarctic ice shelves shows critical ice shelf regions, where local thinning increases the ice flow from the continent into the ocean [Credit: modified from Reese et al., 2018]

Changes in the ice shelves surrounding the Antarctic continent are responsible for most of its current contribution to sea-level rise. Although they are already afloat and do not contribute to sea level directly, ice shelves play a key role through the buttressing effect. But which ice shelf regions are most important for this?


The role of ice-shelf buttressing

Schematic ice-sheet-shelf system: buttressing arises when an ice shelf is laterally confined in an embayment or locally grounds at pinning points [Credit: Ronja Reese & Maria Zeitz]

In architecture, the term “buttress” is used to describe pillars that support and stabilize buildings, for example ancient churches or dams. In analogy to this, buttressing of ice shelves can stabilize the grounded ice sheet (see this blog article about the marine ice sheet instability). It can be understood as a backstress that the ice shelf exerts on the grounding line – the line that separates the grounded ice from the floating ice shelves. When an ice shelf thins or disintegrates, this stress can be reduced, then the ice flow upstream is less restrained and can increase.

This effect has been widely observed in Antarctica: the thinning of ice shelves in the Amundsen Sea is driven by the ocean and linked to ice loss there (see this blog article) and after the spectacular disintegration of Larsen A and B ice shelves the adjacent ice streams accelerated.

Which ice shelf regions are important?

Risk maps show how important each ice-shelf location is: if an ice shelf thins in this location, how much does the flux across the grounding line increase? We estimated this immediate increase using the numerical ice-flow model Úa. At first glance, one can see that all ice shelves have regions that influence upstream ice flow, and thus, provide buttressing. The highest responses occur near grounding lines of fast-flowing ice streams. Equally strong responses are found in the vicinity of ice rises or ice rumples – where the ice shelf re-grounds locally and is subject to basal drag. On the other hand, “passive” regions with negligible flux response are located towards the calving front, but also in spots close to the grounding line. Flux response signals can sometimes travel quite far – for example a perturbation near Ross Island accelerates the ice flow in almost the entire Ross Ice Shelf and reaches ice streams more than 900km away (not visible in the figure).

Risk maps for Antarctic ice shelves, as presented here, help us to get a better understanding of the critical ice shelf regions – if you are interested to read more, please see for example Gagliardini, 2018 and Reese et al., 2018.

Edited by Scott Watson and Sophie Berger


Ronja Reese is a postdoctoral researcher at the Potsdam Institute for Climate Impact Research, Germany, in the ice dynamics working group. She investigates ice dynamics in Antarctic with a focus on ice-ocean interactions and ice-shelf buttressing. She created the risk map together with Ricarda Winkelmann, Hilmar Gudmundsson and Anders Levermann. Contact Email: ronja.reese@pik-potsdam.de

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Image of the Week – Fifty shades of May (Glacier)

Image of the Week – Fifty shades of May (Glacier)

With over 198 000 glaciers in the world, you can always find a glacier that fits your mood or a given occasion. So why not for example celebrate the first Image of the Week of May with a picture of the aptly named May Glacier?


May Glacier is in fact not named after the month, but after Mr May, an officer onboard the Flying Fish during her expedition to the East Antarctic coast in the 1840s. Apart from that, there is not much to say about this 9 x 11 km glacier located in East Antarctica around 130°E, except that it is really hard to find a picture with the keywords “may” and “glacier”… So I let you enjoy the Image of the Week, which combines three satellite images of May Glacier (at the centre) and its surroundings exactly a month ago, when the skies were clear and the sea ice pretty:

See you in a month to talk about the June(au) ice field!

Image of the Week — Cavity leads to complexity

Aerial view of Thwaites Glacier [Credit: NASA/OIB/Jeremy Harbeck].

 

A 10km-long, 4-km-wide and 350m-high cavity has recently been discovered under one of the fastest-flowing glaciers in Antarctica using different airborne and satellite techniques (see this press release and this study). This enormous cavity previously contained 14 billion tons of ice and formed between 2011 and 2016. This indicates that the bottom of the big glaciers on Earth can melt faster than expected, with the potential to raise sea level more quickly than we thought. Let’s see in further details how the researchers made this discovery.


Thwaites Glacier

Thwaites Glacier is a wide and fast-flowing glacier flowing in West Antarctica. Over the last years, it has undergone major changes. Its grounding line (separation between grounded ice sheet and floating ice shelf) has retreated inland by 0.3 to 1.2 km per year in average since 2011. The glacier has also thinned by 3 to 7 m per year. Several studies suggest that this glacier is already engaged in an unstoppable retreat (e.g. this study), called ‘marine ice sheet instability’, with the potential to raise sea level by about 65 cm.

Identifying cavities

With the help of airborne and satellite measurement techniques, the researchers that carried out this study have discovered a 10km-long, 4km-wide and 350m-high cavity that formed between 2011 and 2016 more than 1 km below the ice surface. In Figure 2B, you can identify this cavity around km 20 along the T3-T4 profile between the green line (corresponding to the ice bottom in 2011) and the red line (ice bottom in 2016). According to the researchers, the geometry of the bed topography in this region allowed a significant amount of warm water from the ocean to come underneath the glacier and progressively melt its base. This lead to the creation of a huge cavity.

Fig. 2: A) Ice surface and bottom elevations in 2014 (blue) and 2016 (red) retrieved from airborne and satellite remote sensing along the T1-T2 profile identified in Fig. 2C. B) Ice surface and bottom elevations in 2011 (green) and 2016 (red) along the T3-T4 profile. C) Changes in ice surface elevation between 2011 and 2017. The ticks on the T1-T2 and T3-T4 profiles are marked every km [Credit: adapted with permission from Figure 3 of Milillo et al. (2019)].

What does it mean?

In order to make accurate projections of future sea-level rise coming from specific glaciers, such as Thwaites Glacier, ice-sheet models need to compute rates of basal melting in agreement with observations. This implies a correct representation of the bed topography and ice bottom underneath the glacier.

However, the current ice-sheet models usually suffer from a too low spatial resolution and use a fixed shape to represent cavities. Thus, these models probably underestimate the loss of ice coming from fast-flowing glaciers, such as Thwaites Glacier. By including the results coming from the observations of this study and further ongoing initiatives (such as the International Thwaites Glacier Collaboration), ice-sheet models would definitely improve and better capture the complexity of glaciers.

Further reading

Edited by Sophie Berger


David Docquier is a post-doctoral researcher at the Earth and Life Institute of Université catholique de Louvain (UCL) in Belgium. He works on the development of processed-based sea-ice metrics in order to improve the evaluation of global climate models (GCMs). His study is embedded within the EU Horizon 2020 PRIMAVERA project, which aims at developing a new generation of high-resolution GCMs to better represent the climate.

 

Image of the Week — Into Iceberg Alley

Tabular iceberg, Ross Sea, Antarctica [Credit: Marlo Garnsworthy]

Crew in hardhats and red safety gear bustle about, preparing our ship for departure. A whale spouts nearby in the Straits of Magellan, a fluke waving in brief salute, before it submerges again. Our international team of 29 scientists and 2 science communicators, led by co-Chief Scientists Mike Weber and Maureen Raymo, is boarding the JOIDES Resolution, a scientific drilling ship. We’re about to journey on this impressive research vessel into Antarctic waters known as Iceberg Alley for two months on Expedition 382 of the International Ocean Discovery Program.

Not only are these some of the roughest seas on the planet, it is also where most Antarctic icebergs meet their ultimate fate, melting in the warmer waters of the Antarctic Circumpolar Current (ACC), which races unimpeded around the vast continent. And there, in the Scotia Sea, we will drill deep into the sea floor to learn more about the history of the Antarctic Ice Sheet.


The Drilling Ship

The JOIDES Resolution, our scientific drilling ship [Credit: William Crawford and IODP]

The JOIDES Resolution is a 134-meter-long research vessel topped by a derrick towering 62 meters above the water line. It can drill hundreds of meters into the sea floor to retrieve long cylinders of mud called cores. Analyzing this sediment can tell scientists much about geology and Earth’s history, including the history of Climate Change.

“Sediment cores are like sedimentary tape recorders of Earth’s history,” says Maureen Raymo. “You can see how the climate has changed, how the plants have changed, how the temperatures have changed. Imagine you had a multilayer cake and a big straw, and you just stuck your straw into your cake and pulled it out. And that’s essentially what we do on the ocean floor.”

Our drilling sites in the Scotia Sea. [Figure modified from Weber, et al (2014)]

Our expedition is “going to a place that’s never really been studied before,” adds Maureen Raymo. “In fact, we don’t even know what the age of the sediment at the bottom will be.” Nevertheless, we hope to retrieve a few million years’ worth of sediment, perhaps even more. The sediment cores will provide a nearly continuous history of changes in melting of the Antarctic Ice Sheet.

What can these cores tell us?

As icebergs melt, the dust, dirt, and rocks they carry—known as “iceberg rafted debris”—fall down through the ocean and are deposited as sediment on the seafloor. Analyzing this sediment can tell us when the icebergs that deposited it calved from the ice sheet, and even where they came from. At times when more debris was deposited, we know more icebergs were breaking away from the Antarctic Ice Sheet, which tells us the ice sheet was less stable.

Much shorter cores previously collected at our drilling sites reveal high sedimentation rates, allowing us to observe changes in the ice sheet and the climate on short timescales (from just tens to hundreds of years).

We now know that rapid discharge of icebergs—caused by rapid melting of Antarctic ice shelves and glaciers—occurred in the past, and that episodes of massive iceberg discharge can happen abruptly, within decades. This has huge implications for how the Antarctic Ice Sheet may behave in the future as our world warms.

Where do icebergs come from?

Ok, let’s back up a little—back to where these icebergs were born. Icebergs break off or “calve” from the margins (edges) of ice shelves and glaciers. Ice shelves are floating sheets of ice around the edges of the land. They are important because they have a “buttressing” effect—that is, they act as a wall, holding back the ice behind them. Glaciers are great flowing rivers of ice that grind their way across the land, picking up the rocks and dirt that become iceberg-rafted debris.

Thwaites velocity map animation [Credit: Kevin Pluck, Pixel Movers & Maker]

Most Antarctic icebergs travel anti-clockwise around Antarctica and converge in the Weddell Sea, then drifting northward into the warmer waters of the Antarctic Circumpolar Current.

Iceberg flux 1976-2017  [Credit: Kevin Pluck & Marlo Garnsworthy, Pixel Movers & Makers]

As our planet warms due to our greenhouse gas emissions, warmer ocean currents are melting Antarctica’s massive glaciers from below, thinning, weakening, and destabilizing them. In fact, the rate of Antarctic ice mass loss has tripled over the last decade alone.

Polar researchers predict that global sea level will rise up to one meter (around 3.2 feet) by the end of this century, and most of this will be due to melting in Antarctica. And if vulnerable glaciers melt, the West Antarctic Ice Sheet is more likely to collapse, raising sea level even further.

Blue is old ice, Mc Murdo Sound, Antarctica [Credit: Marlo Garnsworthy]

 

A Hazardous Voyage

We face several hazards on this journey. We are hoping we won’t encounter sea ice, as our vessel is not ice-class, but it’s something we must watch for, especially later in the cruise as winter draws nearer. It is certain that, at times, we’ll experience a sea state not conducive to coring—or to doing much but swallowing sea-sickness medication and retiring to one’s bunk. In heave greater than 4–6 meters, operations must stop for the safety of the crew and equipment.

Of course, our highly experienced ice observer will be ever on the lookout for our greatest hazard—icebergs, of course! We are likely to encounter everything from very small “growlers” to larger “bergy bits” to massive tabular bergs. In fact, it is the smaller icebergs that present the most danger to the ship, as large icebergs are both visible to the eye and are tracked by radar, while smaller ones can be more difficult to detect, especially at night. Nevertheless, we are intentionally sailing into the area of highest iceberg concentration and melt.

“My hope,” says Mike Weber, “is that our expedition will unravel the mysteries of Antarctic ice-sheet dynamics for the past, and this may tell is something about its course in the near future.”

“Bergy bit”, Ross Sea, Antarctica [Credit: Marlo Garnsworthy]

Edited by Sophie Berger


The JOIDES Resolution is part of the International Ocean Discovery Program and is funded by the US National Science Foundation.

Marlo Garnsworthy is an author/illustrator, editor, science communicator, and Education and Outreach Officer for JOIDES Resolution Expedition 382 and previously NBP 17-02. She and Kevin Pluck are co-founders of science communication venture PixelMoversAndMakers.com, creator of the animations in this article.

Image of the Week – Seven weeks in Antarctica [and how to study its surface mass balance]

Figure 1 – Drone picture of our field camp in the Princess Ragnhild coastal region, East Antarctica. [Credit: Nander Wever]

After only two months of PhD at the Laboratoire de Glaciologie of the Université libre de Bruxelles (ULB, Belgium), I had the chance to participate in an ice core drilling campaign in the Princess Ragnhild coastal region, East Antarctica, during seven weeks in December 2018 – January 2019 for the Mass2Ant project. Our goal was to collect ice cores to better evaluate the evolution of the surface mass balance in the Antarctic Ice sheet. Despite the sometimes-uncomfortable weather conditions, the ins and outs of the fieldwork and the absence of friends and family, these seven weeks in Antarctica were a wonderful experience…


Mass2Ant

Mass2Ant is the acronym of the project: “East Antarctic surface mass balance in the Anthropocene: observations and multiscale modelling”. This project aims to better understand the processes controlling the surface mass balance in East Antarctica, its variability in the recent past and, ultimately, improve the projections of mass balance changes of the East Antarctic ice sheet.

What exactly is the surface mass balance?

The mass balance of an ice sheet (see Fig. 2) is the net balance between the mass gained by snow accumulation and the loss of mass by melting (either at the surface or under the floating ice shelves) and calving (breaking off of icebergs at the ice shelves fronts).

The surface mass balance on the other hand only considers the surface of the ice sheet. It is thus, for a given location, the difference between:

  • incoming mass: snowfall, and
  • outgoing mass, due to melting processes (fusion and sublimation), meltwater runoff and transport or erosion by wind at the ice sheet interface.

Figure 2 – Representation of the mass balance of an ice sheet [Credit: Figure adapted from NASA, Wikimedia Commons].

Overall, the ice sheet mass balance – the principal indicator of the “health state” of an ice sheet – is the balance between the surface mass balance, iceberg calving and basal melt under the ice shelves. A good evaluation of these three factors is thus essential to better quantify the evolution of the Antarctic mass balance under anthropogenic warming and therefore its contribution to future sea level rise.

However, the surface mass balance is characterized by strong temporal and spatial variations (see Figure 3) and is poorly constrained. In order to improve future projections for Antarctica, it is essential to better assess the variability of the Antarctic surface mass balance by directly collecting data in the field. Within this framework, the goal of the Mass2Ant project is to study the surface mass balance in the Princess Ragnhild coastal region (marked in the Figure 3).

Figure 3 – Surface mass balance (1989-2009) from RACMO2 (a regional climate model) of Antarctica (left) and Greenland (right) in kg/m².yr. Contour levels (dashed) are shown every 500 m. Black dot is the approximative position of the drilling site on the Tison Ice Rise. [Credit: adapted from Figure 1 of van den Broeke et al. (2011)].

Collecting the data [or how can we use ice cores to infer surface mass balance?]

Surface mass balance can be determined by analyzing ice core records. As a part of our expedition, ice cores were collected on the summit of the so-called “Tison Ice Rise” (a non-official name) – 70°S 21°E, near the Belgian Princess Elisabeth Station. We drilled to a depth of 260.1 m, which we expect to date back to the 15th century.
The drilling system, named the Eclipse drill, contains a motor on top of a drill barrel – which is composed of an inner barrel that cuts the ice core with 3 knives and collects it and an outer barrel (a tube) that collects the chips created. Due to the overlaying ice, pressure increases very quickly with depth. Deep ice cores are thus subject to much higher pressure than the atmospheric pressure. In order to reduce these strong pressure differences as the ice core is brought to the surface, drilling fluid was poured in the boreholes, a technique called “wet-drilling”. This was the first time the wet-drilling technique was used by our team, and it significantly improved the quality of our ice cores compared to the traditional method used during the previous campaigns!

Figure 4 – A part of our team in the drilling tent. An ice core can be observed in the inner barrel of the drilling system. A wooden box is placed on top of the trench, under the drill barrel to collect the chips contained in the outer barrel. [Credit: Hugues Goosse]

The 329 collected ice cores will be analyzed in our lab in Brussels. More specifically, we will focus on

  • the water stable isotopes: the seasonal cycle of stable isotopes of water in ice will be used for relative dating of the ice core;
  • the major ions (Na+, nssSO4, Na+/SO42-, NO3…) present in the ice: the reconstruction of the seasonal cycle of these ions allows us to refine the isotopic dating and therefore infer the annual snow/firn/ice thickness.
  • the conductivity of the ice, which also shows a clear seasonal signal used for dating. Moreover, the conductivity signal is also reacting to localized extra inputs – for example from past volcanic eruptions – therefore providing an absolute dating, which reduces our dating method uncertainties.

The seasonality of these signals will allow us to infer the yearly ice thicknesses (see this post). By taking into account the deformation of the ice, we will then be able to reconstruct the evolution of the surface mass balance in the Princess Ragnhild Coast region since the 15th century.

Life in the field

What was a typical day like for us? In fact, it strongly depended on the team to which you belonged as we were divided into two groups:

  • The “day group” was working on measurements such as snow density and radar analyses and worked roughly between 8 AM and 8 PM.
  • The second group – the drilling team, including me – worked during nights (between 9 PM and 9 AM) because of the too high temperatures during day, which would lead to ice core melt.

The drilling team adapted quite easily to this timing as the sun was shining 24 hours a day. In order to spend a common moment, a joint meal was organized every day at 8.30 AM, with some of us having their dinner while others were having breakfast.
The everyday life mainly occurred in two equipped containers. The first container was our living space, which we used as kitchen, dining room and working space. The second container consisted of a cloakroom, the toilets and the bathroom (with a real shower, a luxury in the field!). Each of us had a tent to sleep, with adapted sleeping bag, making it quite comfortable. As we stayed 5 weeks at the drilling site, we spent Christmas and New Year’s Eve on the field. It was a good occasion to eat fondue while sharing some fun stories and jokes (Fig. 5).

Figure 5 – Christmas time spent together, giving presents and eating fondue. [Credit: Nander Wever]

Why should you too go to Antarctica?

I’ll keep many memories of the time we all spent together, but also of the amazing landscapes and the calm and peacefulness of this white immensity… Despite the sometimes-uncomfortable weather conditions (a full week of whiteout days, lucky us!), this unique experience was wonderful! I’ve learned so much, from a scientific but also personal point of view. It was also a chance to participate in the collection of the samples that I will study during the next four years of my PhD. Before I left for Antarctica, someone told me that “When you went to Antarctica once, you usually want to go again”. Well, that’s definitely true for me!

Many thanks to belspo for funding this project, to the International Polar Foundation and Princess Elisabeth Antarctica staffs for the work both in Cape Town and in the station, and last but not least, thanks to the Mass2Ant team in the field that made this experience an amazing adventure.

Further reading

Edited by Violaine Coulon


Sarah Wauthy is a PhD student at Laboratoire de Glaciologie, Université Libre de Bruxelles, Belgium. Her PhD is part of the Mass2Ant project and aims at determining paleo-accumulation in the region of the Princess Ragnhild Coast (Dronning Maud Land, East Antarctica) as well as the paleo-extension of sea ice before and across the Anthropocene transition (ca. last 3 centuries), by performing high-resolution multiparametric analyses on ice cores collected during field campaigns.

Image of the Week – What’s Hot in the Cryosphere? A 2018 review

Image of the Week – What’s Hot in the Cryosphere? A 2018 review

Every year, humanity understands more and more about a remote and unforgiving component of the Earth system – the cryosphere. 2018 has been no exception, and in this blog post we’ll take a look at some of the biggest scientific findings of cryospheric science in 2018. We will then look forward to 2019 and beyond, to see what the future holds for these rapidly changing climate components.


The Cryosphere at 1.5°C warming

In 2018, the IPCC (Intergovernmental Panel on Climate Change) released their report that looked at the impact of 1.5 and 2.0°C of global warming by 2100 on the Earth system. In the Arctic, warming is already in excess of 2.0˚C, driving a very strong decreasing trend in the summer sea-ice extent. The IPCC suggest that sea-ice-free summers will occur once per century at 1.5°C, but this increases to once per decade at 2.0°C. Limiting warming to 1.5˚C will also save 1.5-2.5 million km2 of permafrost thaw (preventing the release of ancient carbon into the atmosphere), 10 cm of sea-level rise contribution from ice sheets and glaciers, and reduce the risk of the irreversible collapse of the ice sheets. Read more about the cryosphere under 1.5°C warming in this previous post.

 

Mass Balance of the Antarctic Ice Sheet

Compiling 24 independent estimates of mass balance, from a number of different remote sensing and modelling techniques, the IMBIE team produced the best estimate of how Antarctica is responding to continued climate warming. The mass balance refers to the net change in ice mass, accounting for all of the inputs and outputs to the ice. They quantify that ice mass loss from West Antarctica has increased three-fold between 1992 and 2017, largely due to melting from a warmer ocean. On the Antarctic Peninsula, the collapse of ice sheets has led to an increase ice mass loss by a factor of 4. East Antarctica is gaining mass slightly, although this is highly uncertain, by 5 ± 46 billion tonnes per year. Overall, Antarctica has lost 2,720 ± 1,390 billion tonnes of ice in this 25-year time period, and this mass loss is accelerating. Read more about these results in this previous post.

Mass loss from the Antarctic ice sheet is accelerating, largely due to ocean warming impacting West Antarctica. East Antarctica is very slightly gaining mass, but this doesn’t go anywhere near balancing out mass loss across the continent [Credit: NASA Goddard].

A polluted cryosphere

It’s easy to think of the cryosphere as a pristine, beautiful, untouched landscape. However, research from 2018 has shown us that the remoteness of Polar Regions has not protected them from man-made pollution. In one litre of melted Arctic sea-ice, 234 particles of plastic and over 12,000 particles of microplastics were found, which will only go onto adversely impact Arctic wildlife by spreading through the ecosystem. Radioactive material from the Chernobyl accident has also been found to be concentrated in dark sediments found on Swedish glaciers. As these glaciers melt, this concentration of radioactive material may be released in meltwater. In Greenland, lead pollution found in ice cores has provided exciting new insight into wars, plagues and invasions during the Roman Empire.

In 2018, we saw a glimpse of the geological secrets that Greenland hides beneath its ice sheet. However, there is still a hidden world that future field-based campaigns or airborne radar missions will help to unravel [Credit: NASA Goddard].

What secrets is Greenland hiding?

In 2018, we got our best ever look beneath the Greenland ice sheet. Scientists from the British Antarctic Survey and NASA found that the hotspot (a thermal plume in the Earth’s mantle) currently under Iceland was once beneath Greenland, between 80 to 50 million years ago. This hotspot was discovered by studying the magnetism of minerals beneath the ice. Using airplanes, radio waves and sediment that’s washed out from underneath the ice sheet has also revealed a massive 31 kilometre wide meteorite crater underneath Hiawatha glacier. Given it’s beneath three kilometres of ice, the age of this crater is unknown, but given the interest and speculation in connecting this event to an abrupt cooling period 12,000 years ago (the Younger Dryas), we may know very soon.

 

Blast Off!

Satellites remain one of the most popular methods of monitoring the vast, hostile cryosphere. In 2018, a new generation of earth observation missions launched. ESA’s Sentinel-3B continues the Copernicus programme, monitoring the reflectivity of the ice, elevation and sea-ice thickness. NASA’s GRACE FO mission continues the successful first GRACE mission, which used gravimetry to ‘weigh’ different regions of ice. NASA also launched ICESat-2, which will provide global elevation data at unprecedented spatial resolution on a 91-day repeat orbit. Each satellite is being finely tuned to make sure it’s working exactly as intended, and we’ll get the first science from them in 2019. Stay tuned!

Remote sensing data has provided us with answers to some of the biggest questions in the cryosphere. We use it to help quantify mass loss, sea-level rise and glacial retreat. In 2019, new missions will take our knowledge of cryospheric sciences to new heights! [Credit: Liam Taylor]

A look ahead to 2019

On the ground, getting inside the ice will continue to provide fascinating insights into the history of the cryosphere – from reconstructing winds in sub-Antarctic islands using ice cores, to further insights deep inside the world’s highest glacier. As permafrost continues to thaw, we are likely to hear of more discoveries of woolly mammoths, ancient diseases and carbon release. The IPCC will also publish their special report devoted to The Ocean and Cryosphere in a Changing Climate, which will provide the best overall state of the cryosphere to date. And, of course, the infamously named ‘Boaty McBoatface’ will provide us with incredible data from beneath sea-ice and ice shelves when the RRS Sir David Attenborough is launched. 2018 has been a truly exciting year to be a cryospheric scientist, and 2019 looks set to be another hot one!

 

Edited by Adam Bateson


Liam Taylor is a PhD student at the University of Leeds and Centre for Polar Observation and Monitoring. His research looks at identifying novel remote sensing methods to monitor mountain glaciers for water resource and hazard management. He is passionate about climate change and science communication to a global audience, as an educator on free online climate courses and through his personal blog. You can find Liam on Twitter.