Ice Alive: Uncovering the secrets of Earth’s Ice

You have to respect glaciologists whose curiosity takes them to the most extreme places, in this case the Arctic.  Joseph Cook received the Rolex award for Science in Extremis and he provides at his blog a wonderful 20 minute video explaining his work.  From Ice Alive: Uncovering the secrets of Earth’s Ice by Joseph Cook and Chris Hadfield.  Excerpts from below in italics.

In collaboration with Rolex Awards for Enterprise, Proudfoot Media and I have produced a documentary film explaining the latest research into the surprising hidden biology shaping Earth’s ice. The story is told by young UK Arctic scientists with contributions from guests including astronaut Chris Hadfield and biologist Jim Al-Khalili. We went to great lengths to make this a visually striking film that we hope is a pleasure to watch and communicates the otherwordly beauty and incredible complexity of the Arctic glacial landscape. We aim to educate, entertain and inspire others into exploring and protecting this most sensitive part of our planet in their own ways.

We think the film is equally suited to the general public as school and university students, and we are delighted to make this a free-to-all teaching resource. Please watch, share and use!

Albedo is the survival probability of a photon entering a medium. Light incident upon a material partly reflects from the upper surface, the remainder enters the medium and can scatter anywhere there is a change in the refractive index (e.g. a boundary between air and ice, or ice and water, etc). Where there are opportunities for scattering, light bounces around in the medium, sometimes preferentially in a certain direction depending upon the optical properties of the medium (ice is forward-scattering) but always changing direction to some extent each time it scatters, until it is either absorbed or it escapes back out of the medium travelling in a skywards direction.

The albedo of the material is the likelihood that the down-welling light entering the medium exits again later as up-welling light. The more strongly absorbing the material, the more likely the light is to be absorbed before exiting. Ice is very weakly absorbing in blue wavelengths (~400 nm), becoming generally more strongly absorbing at longer wavelengths into the near infra-red (hence ice often appearing blue). Solar energy is mostly concentrated within the wavelength range 300 – 5000 nm and the term albedo concerns the survival probability of all photons with wavelengths within this range either at a particular wavelength (spectral albedo) or integrated over the entire solar spectrum (broadband albedo).

For a single material, its absorbing and scattering efficiencies are described using the scattering and absorption coefficients. The ratio of these two coefficients is known as the single scattering albedo (SSA), which is a crucial term for radiative transfer. A higher SSA is associated with a greater likelihood of a particle scattering a photon rather than absorbing it. a particle with SSA = 1 is non-absorbing.

Algal cells are strongly absorbing and their effect on snow and ice albedo is to increase the likelihood of a photon being absorbed rather than scattered back out of the medium. For this reason, the better term to use would be bio-co-albedo, where co-albedo describes the fraction of incident energy absorbed by the particles (i.e. 1-SSA).

Albedo is a primary driver of snow melt. For clean snow and snow with black carbon, radiative transfer models to an excellent job of simulating albedo, yet there remain aspects of snow albedo that are poorly understood. In particular current models do not take into account algal cells that grow and dramatically discolour ice in some places (except our 1-D BioSNICAR model) and few take into account changes in albedo over space and time.

This led me to wonder about using cellular automata as a mechanism for distributing albedo modelling using radiative transfer over three spatial dimensions and time, and also enabling a degree of stochasticity to be introduced to the modelling (which is certainly present in natural systems).

As an Arctic scientist I am privileged to be able to explore the coldest parts of our planet, making observations and measurements and helping others to understand how these areas function by writing papers and giving talks, lectures and writing for magazines and newspapers. But to truly understand an environment, we must also explore the intangible and immeasurable. To communicate it to diverse audiences, we must use not only facts and observations, but aesthetics and emotion. The piece above is a bridge connecting music and science – an effort to understand and communicate the hidden beauty, complexity and sensitivity of the Greenland Ice Sheet through sound. I hope that projects like this will bring new audiences to Arctic science, using music, art and aesthetics to pique their curiosity.

Footnote:

The video mentions algae as a positive feedback:  more warming>more algae>less albedo>more warming.  However, there are also negative feedbacks operating in summertime.  More warming>more open water>more evaporation>more clouds>less sunshine on the surface.  Also, more evaporation>more snowfall>whiter surface>higher albedo>less solar absorption.

More on sea ice dynamics: Climate on Ice: Ocean-Ice Dynamics

 

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One comment

  1. Hifast · June 11

    Reblogged this on Climate Collections.

    Like

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