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Open AccessArticle

An Under-Ice Hyperspectral and RGB Imaging System to Capture Fine-Scale Biophysical Properties of Sea Ice

1
Institute for Marine and Antarctic Studies, College of Sciences and Engineering, University of Tasmania, Private Bag 129, Hobart 7001, Tasmania, Australia
2
Australian Antarctic Division, Department of the Environment and Energy, Australian Government, Kingston 7050, Tasmania, Australia
3
Australian Antarctic Program Partnership, University of Tasmania, Hobart 7001, Tasmania, Australia
4
Discipline of Geography and Spatial Sciences, School of Technology, Environments and Design, College of Sciences and Engineering, University of Tasmania, Private Bag 76, Hobart 7001, Tasmania, Australia
*
Author to whom correspondence should be addressed.
Remote Sens. 2019, 11(23), 2860; https://doi.org/10.3390/rs11232860
Received: 26 September 2019 / Revised: 3 November 2019 / Accepted: 16 November 2019 / Published: 2 December 2019
Sea-ice biophysical properties are characterized by high spatio-temporal variability ranging from the meso- to the millimeter scale. Ice coring is a common yet coarse point sampling technique that struggles to capture such variability in a non-invasive manner. This hinders quantification and understanding of ice algae biomass patchiness and its complex interaction with some of its sea ice physical drivers. In response to these limitations, a novel under-ice sled system was designed to capture proxies of biomass together with 3D models of bottom topography of land-fast sea-ice. This system couples a pushbroom hyperspectral imaging (HI) sensor with a standard digital RGB camera and was trialed at Cape Evans, Antarctica. HI aims to quantify per-pixel chlorophyll-a content and other ice algae biological properties at the ice-water interface based on light transmitted through the ice. RGB imagery processed with digital photogrammetry aims to capture under-ice structure and topography. Results from a 20 m transect capturing a 0.61 m wide swath at sub-mm spatial resolution are presented. We outline the technical and logistical approach taken and provide recommendations for future deployments and developments of similar systems. A preliminary transect subsample was processed using both established and novel under-ice bio-optical indices (e.g., normalized difference indexes and the area normalized by the maximal band depth) and explorative analyses (e.g., principal component analyses) to establish proxies of algal biomass. This first deployment of HI and digital photogrammetry under-ice provides a proof-of-concept of a novel methodology capable of delivering non-invasive and highly resolved estimates of ice algal biomass in-situ, together with some of its environmental drivers. Nonetheless, various challenges and limitations remain before our method can be adopted across a range of sea-ice conditions. Our work concludes with suggested solutions to these challenges and proposes further method and system developments for future research. View Full-Text
Keywords: sea ice; ice algae; biomass; hyperspectral imaging; fine-scale; photogrammetry; under-ice; underwater; antarctica; structure from motion sea ice; ice algae; biomass; hyperspectral imaging; fine-scale; photogrammetry; under-ice; underwater; antarctica; structure from motion
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MDPI and ACS Style

Cimoli, E.; Meiners, K.M.; Lucieer, A.; Lucieer, V. An Under-Ice Hyperspectral and RGB Imaging System to Capture Fine-Scale Biophysical Properties of Sea Ice. Remote Sens. 2019, 11, 2860.

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