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Bonnie Light
The research I am conducting in the APL-UW Cryosphere Science Laboratory "Freezer Lab" will be shared with a wide audience this year thanks to a television film crew working for the National Geographic Channel. An episode of Naked Science, a popular science show that airs on the cable channel, will explore Snowball Earth. The production company had heard that I was working on a project making laboratory measurements applicable to this extreme climate state and decided they wanted to include an experimental scientist at work in her laboratory to explain what Snowball Earth may have been like.
Snowball Earth refers to an extreme climate state that is hypothesized to have occurred approximately 600 million years ago. It is thought that around this time, the planet suffered at least one complete or near complete glaciation. While nobody knows for certain whether such an extreme climate prevailed, and there are plenty of skeptics, there is considerable geologic evidence that ice sheets, glaciers, and sea ice advanced to very low latitudes. Furthermore, the possibility of such an extreme climate state has implications for the evolution of life on Earth. The glaciation appears to have immediately preceded the "Cambrian explosion" — the rapid appearance of most major groups of complex animals in the fossil record around 530 million years ago. It is not known whether the massive glaciation could have somehow triggered the rapid advancement of species development, but the coincident timing is curious.
I have been working on a project to study one aspect of the physics of sea ice pertinent to Snowball Earth. The project is in collaboration with Stephen Warren (UW Dept. of Atmospheric Sciences) and is funded by the NASA Astrobiology Institute. The objective is to investigate the interactions between solar radiation and sea ice. Because global temperatures are thought to have been considerably colder on Snowball Earth than now, the sea ice that covered the ocean would have been much colder than present sea ice. We really don't know much about this colder sea ice. At temperatures below –22.9°C, some of the salts entrained in sea ice begin to precipitate, dramatically altering the appearance of the ice and its ability to reflect light. In situ observations of ice this cold are rare. Sea ice is typically covered in snow during the cold season, and its surface typically undergoes some melt during the summer season. It's difficult to find natural analogs for really cold sea ice with an exposed surface on Earth, which is why it must be studied in a laboratory.
There is not a lot of laboratory work being done on the topic of Snowball Earth. I produce laboratory grown, salty ice in insulated buckets. I control the temperature, cause the ice surface to sublimate, and watch the precipitated salt crystals accumulate. I also grow the small crystals of precipitated salt in solution and isolate them so that I can document their physical and optical properties.
The Naked Science program will also feature the fieldwork involved in finding, examining, and analyzing geological sites around the world that hold evidence of Snowball Earth. Likewise, there is much to be learned from numerical simulations of the global climate system under forcing conditions hypothesized to have been in place during these events. As a result, the production team spent time at sites in Death Valley and Australia, and interviewed researchers in front of their computer terminals in university offices. In the interest of a balanced production, they were eager to include a segment focused on experimental work, filmed on location in a laboratory.
We worked together for a full day to capture video of the laboratory experiments. I showed how I examine the cold surface of sea ice grown in a laboratory, how I prepare crystals in solution, and how I study samples of natural sea ice extracted from the Arctic in the controlled environment of the cryosphere laboratory. The production team is editing the show in London and expects it to be aired on the National Geographic Channel in May or June. Look for me. I'll be the one wearing the big blue parka.
Watch for the program listing @ http://channel.nationalgeographic.com/channel/nakedscience/
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Bonnie Light is a physicist at APL-UW's Polar Science Center. Her research is focused on how solar radiation interacts with the Earth's cryosphere, in particular, the sunlight incident on the Arctic Ocean sea ice.
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Photomicrograph of hydrohalite crystals in solution at –15°C (note scale at lower left).
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Bonnie inspects buckets of cold laboratory-grown sea ice used to investigate the optical properties of cold sea ice.
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Laboratory for Environmental
Cryosphere Science
This laboratory features two room-size freezers for which temperatures can be controlled individually to as low as –30°C. APL-UW developed this facility to advance the interdisciplinary study of physics, biology, and chemistry at subfreezing temperatures.
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