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by Sarah Boon
Read the outcome of a scientific study and it often seems that the neatly packaged conclusion provided was presented to the researchers in a single, perfectly exposed photograph. In reality it was a puzzle with a lot of behind-the-scenes shuffling of pieces – sometimes trying to figure out exactly what those pieces were – before the entire picture came together.
This happens no matter the scale: individual projects or when the entire research community works toward developing an in-depth understanding of a larger subject, such as tidewater glaciers.
Named for the fact that they terminate in ocean water, tidewater glaciers drain ice from the centre of larger ice masses like the Greenland and Antarctic ice sheets. They can set adrift giant ice islands like the one that recently broke off the Pine Island Glacier (PIG) in Antarctica and are the source of the phenomenal icebergs seen off the coasts of both Newfoundland and Alaska. For more iceberg fun, check out the largest calving event ever filmed, captured in Greenland by the Chasing Ice team. A group at Oregon State University has also recorded the sounds of icebergs.
Since these types of glaciers are found mainly in polar regions, it would be easy to assume they’re irrelevant to us. Not so. Scientists are concerned about tidewater glaciers and their response to climate change, their contribution to sea level rise, their affect on ocean chemistry, and shipping implications as more, and bigger, icebergs are calved.
Figuring out how tidewater glaciers work gets complicated in a hurry, because the ice is interacting not only with the overlying atmosphere, but also with the underlying ocean. This results in a long laundry list of factors that can cause these glaciers to change over seasons, decades and centuries.
13 years ago, my PhD advisor and I were on a barren, scree-strewn ridge in Canada’s high Arctic, looking down on the biggest glacier I’ve ever seen in my life. The whoop-whoop of chopper blades faded into the distance, slinging gear to our summer field site. In the sudden silence, broken only by the wind amongst the rocks, my advisor explained what was known about tidewater glaciers.
While scientists had a good understanding of how these glaciers interacted with the atmosphere, they hadn’t quite figured out the ocean connection. Even our short conversation raised more questions than answers, more potential puzzle pieces to fit into that bigger picture. We talked about the effect of tidal cycles, sea ice, and ocean currents and ocean temperature. We wondered how water exited the glacier as the ice melted, and what happened to ocean properties as the meltwater mixed with ocean water.
Sitting in the pale Arctic sunlight, it seemed we were having our usual on-campus coffee break as we bounced around various technical ideas that could potentially help us understand how these puzzle pieces fit together. Some involved using underwater pods like James Cameron’s Titanic-seeking submarine to explore under the floating glacier terminus. Others required extreme daring when collecting field data, like climbing down crevasses on the calving glacier front to measure their dimensions and collect water samples from their depths. Looking out across the barren landscape, the ideas seemed endless and enormous.
Since that day, much has changed in the field of tidewater glaciology. The puzzle picture is slowly coming together, and it’s pretty cool (no pun intended) to see such progress over my own ‘scientific lifetime’.
One of the big factors that pushed this topic forward was the trend towards forming interdisciplinary teams to answer big research questions. In 2007, we initiated an International Polar Year research project on the Belcher Glacier, an outlet glacier of Canada’s Devon Island Ice Cap. It was the first truly interdisciplinary project I was involved in, and included field researchers in glacier hydrology and meteorology, ice movement and calving, and seafloor bathymetry; oceanographers and remote sensing scientists; and numerical modellers who could write computer programs to recreate the glacier surface energy balance, ice dynamics, and ice-ocean interactions. A similar project on the PIG, led by Bob Bindschadler, is another great example of this disciplinary integration, as it includes glaciologists, oceanographers, remote sensing scientists, meteorologists, and geophysicists.
A second major factor in developing tidewater glacier science has been the introduction of exciting new technologies that complement the research strengths of an interdisciplinary team. For example, automated underwater vehicles (AUVs), one of which was developed right here in Canada at the University of British Columbia (UBC). AUVs are used to explore the ocean under those floating ice tongues, and discover how the two interact. They do this by looking at ice sculpting patterns, and by measuring ocean currents and chemistry, on the bottom of the ice tongue.. Another new technology is airborne ice-penetrating radar, which can image the plumbing system underneath tidewater glaciers just by flying over them. This information is the best way to understand how glacier meltwater gets to the glacier terminus to mix with ocean water.
Researchers now have a broader knowledge base – and are far better equipped – to put together the puzzle pieces required to understand how tidewater glaciers respond to climate change. For example, Luke Copland, at the University of Ottawa, has figured out that iceberg calving isn’t affected by tidal cycles, but more by seasonal variations in sea ice thickness. Marco Tedesco’s team at The City University of New York (CUNY) has identified links between how fast tidewater glaciers move and how much water gets inside the glacier from glacier melt. These examples represent only a fraction of the hundreds of papers now published that explain different aspects of tidewater glacier behavior.
On the flip side, however, it seems that ignorance may really be bliss: the harder we try to put the picture together, the more puzzle pieces appear that we didn’t even know were needed. While I’ve used tidewater glaciers as an example, we could just as easily substitute mountain pine beetle research or cancer research.
It also means that readers of research results – you, me, other scientists – can easily forget that individual studies are also single puzzle pieces within that bigger picture. For example, a study published in Science this year focused on the role of warm ocean water in driving glacier change. The researchers determined that smaller ice shelves are sitting in warmer water than bigger ones, and so lose more mass. This leads to overall shrinking of the ice sheets from which these glaciers drain.
The first comment I saw on this study came from University of Washington glaciologist Eric Steig:
He’s right, of course. While the paper concludes that ocean warming is important for tidewater glacier change, that doesn’t completely rule out the effects of ocean circulation. However, the purpose of the study was to look at many tidewater glaciers instead of just one (as is usually the case), and to use this broad dataset to identify the main drivers of ice loss. Not only that, the paper focused only on the 2007-2008 period, which had the best data. Was Steig expecting too big of a puzzle piece out of this study?
Scientists use hypotheses to constrain their studies to questions that can realistically be answered given available time and money. As readers of scientific literature – whether journal articles, news releases, or popular articles – we need to remember that. One study may have some – but not all – of the answers, and it takes a series of studies combined in new and interesting ways to create that complete puzzle picture. It’s our responsibility to rummage amongst those pieces and figure out that context.
While it’s not all smooth sailing, from where I stand, the tidewater glacier puzzle is looking a lot more complete than it was that windy day on an Arctic ridgeline, 13 years ago.