Spring Quarter: "Bella Donna"- Stevie Nicks
Honors 222: Polar Places & Spaces: "Boom boom"-J. Lee Hooker
GIS Figures: Exploring Greenland's Ice
The western coasts of the Greenland Ice Sheet (GrIS) experience much earlier and faster rates
of glacial retreat and melting than the eastern coasts– predominantly as a result of their low
elevation topography and pronounced depressions in bedrock which enhance the flow of warm
oceans in facilitating ice loss and basal melting. Concurrently, the western coasts are
experiencing amplified growth of pigmented algae on its ice surface and, thus, increased
radiation absorption. There are multiple scientific efforts going towards documenting the extent
of the biomass and its influence on mass loss for the GrIS for the western coast’s glaciers (as
the western coast is not only experiencing retreat earlier, but it is also more densely populated),
but not as many as the eastern. So, for this project I wanted to gain a broad understanding of
algae growth in connection to Glacier extent and retreat on the eastern coast of Greenland–
especially considering that the eastern coast has higher wildlife populations and greater
biodiversity (especially in southeastern Greenland). Indigenous peoples emphasize the
importance of those wildlife and the complex relationships exhibited by such biodiversity, so I
used this idea and the rest of the notions from the Ethical and Equitable Engagement Synthesis
Report to inform the direction of my GIS layer and how I would look at the data. I aimed to
contextualize glacial change and algae influence in relation to the multi-dimensional changes
occurring and the ones going to occur on the Eastern Coast while maintaining a connective and
holistic view of the ecological system.
Sentinel-2 10m Land Use/ Land Cover data produced by Esri and Impact Observatory (2018-2023)
Concentrating on glacial zones with the greatest rate of change of ice column thickness (-1.5 to -2 m/yr), I used QGreenland’s “Ice Column thickness rate of change 2003-2019 (5km)” to determine zones with high thickness depreciations on the eastern coast, and selected the Kangersertuaq Gletsjer and surrounding fjords, islands, and capes for the focus of my layers. I then looked to quantify and visualize snow/ ice, ocean, and bare ground cover over the most recent years, and using Sentinel-2 10m Land Use/ Land Cover data produced by Esri and Impact Observatory, I created a layer in QGIS documenting the ice and ocean extent from 2018-2023.
Sentinel-3 The Terrestrial Chlorophyll Index (OLCI) (2018-2023)
Next, I wanted to contrast this by quantifying and visualizing the higher-biomass algal blooms on the Ice Sheet over the same timespan. Glaciers trap a lot of nutrients, and as such, the melt water directly feeds these nutrients to pigmented algae and amplifies growth on the ice surfaces. Knowing this, we should expect to see larger biomass growth periods during years of net glacial retreat, and lower growth during years of glacial advance. Most studies attempting this will use remote detection to measure the unique chlorophyll absorption features at 680 nm, a broader carotenoid absorption feature, a normalized difference spectral index, and a spectral unmixing model. However, these spectral signatures are ambiguous for glacier algae because the phenolic pigment has a broad absorption range across UV and visible wavelengths. This broad absorption obscures the features associated with other pigments in raw reflectance spectra and is further complicated by the variable optics of the underlying ice and the mixing of algae with other impurities. So, studies will utilize techniques that isolate the spectral signatures of glacier algae to detect and quantify their impact on albedo and melt processes. Sadly, I don’t have access to any of that data (despite requests). As a result, I utilized Sentinel-3 OLCI data to measure chlorophyll content and monitor algae health by assessing the chlorophyll absorption feature, particularly around 680 nm.
In this case, I was using chlorophyll content to broadly demonstrate biomass. The QGreenlandvegetation data classifies this area as glacier, non-carbonate mountain complex, and herb barren. While low OTCI values typically indicate non-vegetative surfaces like water, sand, or snow, and extremely high values might suggest bare ground or clouds, the intermediate values (red to dark green) can indicate varying levels of algae presence. Algae on glacier surfaces would appear in this range, helping to distinguish them from non-biological features.
I used data collected from the month of April, as this is the beginning of ablation season, which yielded chlorophyll counts that allowed me to see how the beginning of ablation compares with algae growth and the overall retreat or advance that occurred in the same year. It’s important to note that the presence of phenolic pigments in glacier algae can mask the detection of the specific spectral signatures– namely, the chlorophyll specific absorption features that OTCI relies on. This makes it difficult to distinguish glacier algae from other impurities using OTCI alone. However, while OTCI may struggle to directly measure the chlorophyll content of glacier algae because of that masking effect, it could still contribute to my overall assessment and my aim to deepen a broad understanding of this system.
During the years of glacial advance, there are lower chlorophyll contents. Vice versa, during years of glacial retreat, there are higher chlorophyll contents.
Honors 222: Polar Places & Spaces: "Sympathy for the Devil"
If I could continue my visualization, I would’ve liked to quantify the effect of glacier algae on albedo and radiative forcing in ice, isolate the spectral signatures of glacier algae, and incorporate the algae and its glacier impacts into a mass balance model. I would be most curious to estimate the biomass contribution to GrIS runoff, but maybe I’ll save that for graduate school!
I can't thank Professor Michelle Koutnik enough for the consideration, communication, and compassion she evoked in each of us, our public science analyses, and our GIS layers. Her guidance allowed for deeply thoughtful conversations, especially around ethical and equitable engagement with Indigenous Knowledge and Indigenous communities.
Learning the accessibility of science is a long journey, which I would encourage every scientist, science enthusiast, and community member to question. This class led with letting community need dictate research direction, discussion, and whether there is even a right to study that research. I aim to use that lead and apply it to my growing questions of how people shape landscapes, and how those landscapes shape people 'in return.' Science is often framed for anthropogenic benefit, and yet those groups of benefit are rarely those existing in any exigency. So, if we are to anthropomorphize ecological importance, might as well do it with true sincerity-- in full consideration of the impacts, rights, and systems we engage in.
Copyright © 2024 Willow Loring Lachlan Ivey Hoins Honors Portfolio - All Rights Reserved.
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