The ‘bioalbedo effect’ is the accelerated melting of snow and ice due to living organisms growing on it. Life can change the colour of the snow or ice, increasing its efficiency as an absorber of solar energy and causing it to heat up. Our new paper, just accepted by Journal of Geophysical Research, uses a predictive numerical modelling approach to examine this process for algal cells growing on snow.
The model can be broken down into distinct parts. The first part is a mixing model for pigments that can be present in snow algal cells. The user can define the relative amounts of each pigment in the cells. The cell wall is assumed to be transparent. This then allows the absorption coefficient for each individual algal cell to be calculated.
The second part of the model scatters these cells in a layer of a hypothetical snow pack. The layer can be any thickness and does not necessarily have to be the surface layer. The amount of algae is expressed by the user in g(algae)/g(snow). The radiative transfer model TARTES has been adapted to account for our algal cells and is used to predict the bihemispheric spectral reflectance of the surface.
The albedo of the snow is then calculated using incoming solar radiation (measured or modelled, e.g. using NASA’s COART model). This can be plotted and analysed, or used to drive an energy balance model to determine how much the algae influence snow melt.
The paper shows that algae have the potential to reduce snow albedo, with the magnitude of their effect dependent upon how much algae is in the snow and how pigmented it is. It also shows that specific wavelengths of light are affected more than others by algal cells and that this could be used diagnostically, perhaps allowing us to detect algae from planes, drones or satellites. The energy balance part of the model shows that this affects how quickly the snow melts. A physical mechanism for algal acceleration of snow melt is thereby developed.
Next, we intend to develop the model so that it is applicable to melting glacier ice as well as snow. This will help us to explain the mysterious ‘dark zone’ on the Greenland ice sheet which is probably discoloured by a combination of dust, black carbon soots and algal blooms.
The model provides a framework for integrating bio-optical and radiative transfer models, demonstrates the potential for algae to melt snow and outlines some of the challenges for empirical bioalbedo measurements. There are improvements still to make to the model, but this work proves the concept that radiative transfer and energy balance modelling can be coupled, and shows how algae can change the colour of snow.
Yesterday I visited the BBC to talk about life on ice with Libby Purves on Midweek on Radio 4. It was the first time I’d been to Broadcasting House and that in itself was a real experience. I was whisked upstairs to the recording studio with the other guests – author Ken Follett and musicians Fr David Delargy and Hannah Peel.
The conversation was led by Libby Purves, who began proceedings by asking the group: “Do you like the cold?”
I was able to tell the group about some the life that exists on ice surfaces and the logistics of working on ice sheets, before finally admitting to having questionable choices on my field camp playlist!
Overall a great opportunity to communicate glacier ecology to a new demographic, and great fun.
Thanks BBC, thanks Libby, thanks Ken, David and Hannah.
I was lucky enough to spend November working at NASA’s Jet Propulsion Laboratory. The purpose was to develop ongoing collaborations with expert glaciologists Johan Nilsson (who joined me in Greenland in the summer) and Alex Gardner, meet new potential collaborators and present my recent work on “bioalbedo”.
It was an extremely productive trip – being face-to-face with these top experts helped to confirm, refine and advance my current work and plans for 2017. I was lucky enough to meet researchers from the Airborne Snow Observatory and Europa Mission and got a tour around some of the labs and talk about potential collaborations.
Speaking at JPL was a huge honour and total boyhood dream-come-true as this is one of the world’s leading centres for cutting edge earth science. I spoke to the Earth Sciences division on the topic of “Bio-albedo” (the effect of microbial life on the colour of ice). The feedback and follow-up conversations were really valuable and will help stimulate some exciting science in 2017!
It also happened to be my 30th birthday while I was out there so to celebrate, Johan, fellow researcher Aumery and I hiked up Mount Baldy before going to the cinema for some appropriately space-themed sci-fi in the evening!
So #thanksNASA for hosting me and showing me the incredible Earth and space science being done at JPL.
I am very pleased to report that I was recently made a 2016 Rolex Young Laureate. This award recognizes potential in young scientists and entrepreneurs (under 30’s), so it is extremely humbling to have been selected. I’ll be delivering a project (“Ice Alive”) that will advance our understanding of ice as a living landscape.
I have already been able to meet some incredibly inspiring people, including my fellow laureates, the jury and the Rolex team, and this award will stimulate some big adventures in 2017 and beyond!
For more information, see my Rolex profile page here.
Interestingly, I’m the second researcher from the University of Sheffield’s Geography Department to receive a Rolex Award, after volcanologist Andrew McGonicle (2008).
Here are two short films that Peter Sinclair (DarkSnow and Climate Crocks) made over summer 2016. The first is an interview with me about Greenlan’s surface reflectivity. The second is about the microbiology of algal blooms on the ice surface by fellow Black and Bloom postdoc Chris Williamson.