Tag Archives: Stephenson Glacier

Heard Island Poster at the 2017 American Geophysical Union Fall Meeting

Glacial ice on the beach at Corinthian Bay, Heard Island. Image credit: Bill Mitchell (CC-BY).
Glacial ice on the beach at Corinthian Bay, Heard Island. Image credit: Bill Mitchell (CC-BY).

In three weeks I will be attending the American Geophysical Union (AGU) fall meeting, and on Thursday morning I will be presenting a poster about the Retreat of Stephenson Glacier, Heard Island, from Remote Sensing and Field Observations.1,2 I am very much looking forward to it, and if you will be at the meeting I hope you will stop by. There is likely to be a journal article forthcoming on this work, and the conference will be a great opportunity to discuss my project with glaciologists and get feedback on it—exactly what poster sessions at conferences are for, from what I understand.

Although my analysis is pretty much done, there is still quite a bit of work to go. Most importantly, the poster needs to be created. For that, I’ll start with a list of graphics and figures that will be needed for the poster:

  • Map of the world, showing the location of Heard Island
  • Map of Heard Island, showing the location of Stephenson Glacier
  • Satellite image(s) of Stephenson Glacier, showing the retreat
  • Field photo(s) of Stephenson Glacier from the Heard Island Expedition3
  • Graph showing the area of the glacier over time
  • Other maps/graphs as needed

From that graphical outline will follow a minimal amount of text to guide a reader through the project with introduction, methods, results, and discussion sections. Once all that gets put together, it gets reviewed, sent to my co-author for further review, then changes are made until we’re satisfied and it’s sent off to the printer.

Following the conference, I hope to get a more detailed manuscript written. When it is ready for submission, I expect it will go to EarthArxiv, a new Earth science pre-print server, as well as an appropriate journal with open-access options.

Publication of that article would be the final step for this project, but there are quite a few new project ideas which have sprung up while I’ve been preparing this poster and article. One of the great things about using openly available data is that there are so many projects which could be done relatively simply and at little cost. Of course, a few other ideas have come to mind—and are perhaps more interesting—that would need further field studies.

Notes:

  1. Poster C41B-1222.
  2. Unless the affiliation is “Unaffiliated” for the lead author, it is incorrect. I have tried to get it corrected, but apparently the system can’t handle that.
  3. During the Heard Island Expedition, although I was close to Stephenson Glacier I was unable to travel to that part of the island. Fortunately my co-author and several other expedition members did get there and took lots of photographs among other sampling and documentation efforts.
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Geoscientist’s Toolkit: QGIS

QGIS screenshot, showing Heard Island.  Brown is land/rock, blue are lagoons, and the dotted white is glacier.
QGIS screenshot, showing Heard Island. Brown is land/rock, blue are lagoons, and the dotted white is glacier.

One of a geoscientist’s most useful tools is a geographic information system, or GIS. This is a computer program which allows the creation and analysis of maps and spatial data. Perhaps the most widely used in academia is ArcGIS, from ESRI. However, as a student and hobbyist who likes to support the open-source software ecosystem, I use the free/open-source QGIS.

QGIS can be used to make geologic maps of an area, chart streams, and note where certain geologic features (e.g. volcanic cones) are present. For instance, at the top of this post is a map of Heard Island that I’ve been playing with, from the Australian Antarctic Division. It is composed of three different layers, each published in 2009: an island layer (base, brown), a lagoon layer (middle, blue), and a glacier layer (top, dotted bluish-white).

I believe I have mentioned here previously that one interesting thing about working with Heard Island is that with major surface changes underway (glacial retreat, erosion, minor volcanic activity), the maps become obsolete fairly quickly. This week I have been learning about creating polygons in a layer, so that I can recreate a geologic map from Barling et al. 1994.[1] One issue I’ve come up against, though, is that the 1994 paper has some areas covered in glacier (from 1986/7 field work), whereas my 2009 glacier extent map shows them to be presently uncovered. In fact, even the 2009 map shows a tongue of glacier protruding into Stephenson Lagoon (in the southeast corner), while recent satellite imagery shows no such tongue.

During the Heard Island Expedition in March and April, 2016, I hope that we will have time to go do a little geologic mapping. Creating some datasets showing the extent of glaciation (particularly along the eastern half of the island) and vegetation, as well as updating the geologic map to include portions which were glaciated in 1986/7, would be a worthwhile and seemingly straightforward project.

QGIS itself is much more than a mapping tool (not that I know how to use it), and can analyze numeric data which is spatially distributed, like the concentration of chromium in soil or water samples from different places on a study site. QGIS provides a free way to get your hands dirty with spatial data and mapping, and is powerful enough to use professionally. Users around the globe share information on how to use it, and contribute to its development.

For those looking to go into geoscience as a career, I would strongly recommend learning how to use it. I didn’t learn GIS in college (chemists don’t use it much), and somehow avoided it in grad school. But I regret not having put time in to learn it sooner. There’s all kinds of interesting spatial data, and a good job market for people with a GIS skillset (or so I hear). I have only scratched the surface of QGIS’s capabilities with my use of it, but I definitely intend to keep learning. You can probably follow the day-to-day frustrations and victories on my Twitter account (@i_rockhopper).

***

[1] Barling, J.; Goldstein, S. L.; Nicholls, I. A. 1994 “Geochemistry of Heard Island (Southern Indian Ocean): Characterization of an Enriched Mantle Component and Implications for Enrichment of the Sub-Indian Ocean Mantle” Journal of Petrology 35, p. 1017–1053. doi: 10.1093/petrology/35.4.1017

Glaciers and City Buses

Central and southern portion of Heard Island, including Gotley glacier.  Image credit: NASA ISS.
Central and southern portion of Heard Island, including Gotley glacier. Image credit: NASA ISS

Heard Island is covered by 41 glaciers.[1] Some of these glaciers, such as Stephenson Glacier, are retreating rapidly, while others, like Gotley glacier in the southwest, have remained steady since 1947 when detailed surveys began.

The glaciers on Heard Island, like glaciers everywhere, act much like a conveyor belt, a giant river of ice. Snow (and rain) falling near the top solidifies into ice and flows downhill, until either the ice melts and flows away as a stream, or the ice meets the ocean and calves (breaks away).

Unlike the conveyor belt analogy, the snow does not only fall at the very head. Indeed, at times, the whole glacier can receive snow, or could be melting at the surface. On average, though, the snow accumulates in the eponymous accumulation region, and melts in the depletion region.

Perhaps a better analogy for a glacier is not a conveyor belt, but a city bus which runs into, and through, a city. Toward the beginning of the route, people board the bus, but very few leave. In the middle of the city, some people come and others go. Finally, as the bus leaves the city toward the surrounding area, more people leave than get on, and after reaching the end of the route, the bus is empty of passengers.

To really get a grasp of how glaciers work, you might want to try this Java-based simulation (helpful activity guide). One aspect of glaciers that becomes apparent in the simulation is that the surface of a glacier moves more rapidly than its base. There’s a tool to let you drill a virtual hole in the ice, then watch as the hole gets stretched out as the glacier flows downhill.

Now that you’ve spent a while playing around with the simulation—I certainly have—let’s take a look at the glaciers of Heard Island.

As I mentioned before, some glaciers are retreating, while others are relatively unchanged. Several factors influence the size of glaciers: precipitation amount, freezing level (of the atmosphere) [generally related to sea level surface temperature], relative humidity, albedo (reflectivity), and the thickness of rocky debris cover.

Precipitation and the freezing level are fairly straightforward factors: more snow and cooler temperatures yield larger glaciers. But there are complications! In a windy environment, such as that of Heard Island, snow doesn’t just pile up evenly as it falls; it drifts. Snow that falls in one place may end up being picked up by the wind and deposited somewhere downwind. This effectively adds precipitation to downwind areas, and removes it from upwind areas.

Relative humidity is important to glacier size, because even cold, dry air can cause snow and ice to sublimate—turning directly from solid to gas. In places like the McMurdo Dry Valleys in Antarctica, this effect keeps the valleys from filling with snow and ice. On Heard Island, a shift in the wind, or a more steady wind direction, can cause different areas to be affected by these dry winds, or to be affected more than in years past.

Here are some of Ruddell’s comments on the matter of why some glaciers are retreating and others do not:[1]

The accumulation, distribution and snowline elevation on many Heard Island glaciers appears to be influenced strongly by the re-distribution of snow by the wind. The prevailing wind direction is westerly and there is less likely to be a re-distribution of snow to low elevations on the westerly facing glaciers… Further, the re-distribution of snow by wind on west-facing glaciers is likely to be impeded not only by wind speed and direction but by severe crevassing (e.g., Gotley Glacier).

When the Heard Island expedition arrives this (austral) November, the glaciers can be observed from close range, rather than by satellite. An additional topic of interest is documenting the advance of vegetation toward recently de-glaciated areas.

During the 1947-2000 period, the glaciers on Heard Island showed an overall reduction in area of 12%.[1] The trend has been toward retreat, and with temperatures increasing about 0.8 °C since 1947, the glacier areal coverage in 2015 is almost certain to be lower still.

***

[1] Ruddell, A. “An inventory of present glaciers on Heard Island and their historical variation”, in Heard Island: Southern Ocean Sentinel (Eds K. Green and E. Woehler) Surrey Beatey & Sons, 2006, p. 28-51.

Topographic Map(s) of Heard Island, and a Big Landslide

Heard Island Map, 1985.  Image credit: excerpt from the Division of National Mapping.
Heard Island Map, 1985. Image credit: excerpt from the Division of National Mapping.

A few days ago, I posted about topographic maps, including a discussion of how a small army of small surveyors made one of my local park. At Heard Island, surveying isn’t a walk in the park.

Many maps have been made of Heard Island, showing the topography and general geographic features of the island, and sometimes including the locations of major macrofauna (penguins, elephant seals, etc.).[1] An excerpt I made from one produced in 1985 is shown above. Although there are more recent maps available, including maps with higher topographic resolution, this one is more visually illustrative of the landforms.

Maps of Heard Island are difficult to produce, in part because there is a dearth of high-resolution, high-quality data. In most parts of the developed world, detailed topographic maps are made not through boots-on-the-ground surveying but by airborne LiDAR. For instance, aerial imagery and LiDAR provided very useful data for understanding the Oso landslide in Washington state. However, aerial flights over Heard Island are much less frequent, and mapping efforts there come without the obvious benefits to the local populace.

LiDAR map near the Oso landslide (red region at right), and a larger landslide complex (red region at center).  Image credit: Dan McShane.
LiDAR map near the Oso landslide (red region at right), and a larger landslide complex (red region at center). Image credit: Dan McShane.

Surveying the whole island by foot at high detail is untenable, because the area is quite large, the terrain difficult, and the weather inclement, even in the summer. However, portions have been mapped by hand (and theodolite).

But perhaps the biggest challenge Heard Island presents to cartographers is the rapidity of its changes. Volcanic eruptions can add new land to the island, or make parts higher. Glaciers can carve out the rocks and leave them as till, sometimes in the ocean, sometimes in the lagoons, and sometimes as moraines on the land. Not only can the glaciers carve out the rocks, but as less snow accumulates on the glaciers than is lost to melting, the glaciers will retreat. This opens up new land which before had been covered in ice. Stephenson Glacier, on the southeast corner of Heard Island, has retreated significantly in the last 60-70 years, revealing a great deal of new terrain.

Steep slopes and the very wet environment (lots of snow and rain) lead to very high rates of erosion. Outwash channels from the glaciers can carve into the rock and transport sediment into lagoons and near-shore areas.

Finally, there’s another agent of change: landslides. Take a look at the LiDAR image above, showing the landslide region. Now take a look at the southwest portion of the Heard Island shown at the top of the post. The curving crest along the north and east sides of the volcano, as well as the ridge extending to the south-southwest are interpreted to be the boundary (technical term: scarp) of a debris avalanche (a landslide-like process).[2]

Taken as a whole, these processes change the landscape significantly on a decade-to-century timescale, if not even more rapidly. This is why making maps and keeping them current is so valuable: it give us a way to see how the landscape is changing over time. Perhaps the upcoming Heard Island Expedition will do some mapping and be able to provide updates which reflect the latest changes at Heard Island.

[1] https://www1.data.antarctica.gov.au/aadc/mapcat/list_view.cfm?list_id=1, accessed Feb. 6, 2015. Free registration required for map download.

[2] Quilty, P. G. & Wheller, G. 2000; Heard Island and The McDonald Islands: a Window into the Kerguelen Plateau. Papers and Proceedings of the Royal Society of Tasmania. 133 (2), 1–12.

Global Warming, and Stephenson Glacier Retreat

Annual global surface temperature difference from the 20th century average.  2014 is the 38th straight year above average.  Image credit: NOAA.
Annual global surface temperature difference from the 20th century average. 2014 is the 38th straight year above average. Image credit: @NOAA.

Two things came to my attention today which are of particular interest.

First, NOAA has announced that globally, 2014 was the warmest year on record, and the 38th straight year of above-average temperatures. Continued action will be needed in 2015 to reverse this trend. Every delay makes fixing the situation more difficult.

Second, Mauri Pelto has written today about the retreat of Stephenson Glacier and the formation of a lagoon on Heard Island. In 1947-1948, when members of the Australian National Antarctic Research Expedition (ANARE) spent 15 months at Heard Island, they found Spit Point, on the southeast side of the island, was only accessible after crossing Stephenson Glacier. Imagery from LANDSAT shows substantial retreat, as do photographs from a 2004 expedition to Heard Island.

Landsat 2010 image, annotated by Mauri Pelto.  Arrows mark the toe of the glacier in 2001 (purple), 2010 (red), and 2013 (yellow).  Additional images are available on Mauri Pelto's blog.
Landsat 2010 image, annotated by Mauri Pelto. Arrows mark the toe of the glacier in 2001 (purple), 2010 (red), and 2013 (yellow). Additional images are available on Mauri Pelto’s blog.

Today, where once Stephenson Glacier met the ocean, there is now Stephenson Lagoon. The toe of the glacier has retreated inland, and to my eye appears to have moved about 4 km. With a warming at Atlas Cove of 1 °C over 1947-2001, the retreat is not surprising.