Enhanced Ocean Colour Remote Sensing for Optically Complex Waters

Informations

Funding country

Norway

Acronym

-

URL

-

Start date

1/1/2020

End date

12/31/2024

Budget

982,770 EUR

Fundings

Abstract

The climate on earth is changing, and the ocean, covering 71% of the surface, plays a significant part. In coastal regions there are much more particles in the water compared to the open seas, making the optical properties of the water more complex. Both particle type and concentration can answer questions on how the marine ecosystem is changing with the climate. Optical measurements in coastal waters and fjords, combined with water samples, are important to map these changes. In spring and early summer it is common that the sea and fjords in western Norway turn completely green. Usually this is due to algal blooms or because glaciers are melting and transport large amounts of sand and clay into the water. The green colors of these two cases can look very similar, and it can be very hard to distinguish them on satellite images. About 90% of the light reaching a satellite originates from the atmosphere, not the water it wants to take a closer look at. Therefore it is crucial to have good atmospheric corrections to remove light not coming undisturbed from the water. The EcoSens project has two main parts: 1) We will measure the optical properties of the water directly, and then 2) use the measurement results in models to improve atmospheric corrections. Thereby we will both maps the water constituents and be able to interpret satellite images better. This way we can close in on a goal of being able to identify oceanic particles via remote sensing. In the project's first year we have had a very successful field work campaign in Marifjøra. We completed many different optical measurements in Gaupnefjorden in the transition between spring and summer, when the fjord is completely green/turquoise due to meltwater from Jostedalsbreen glacier. In addition, we have hired a PhD-student, who has started well by analysing satellite images from this area in the same time period. We are working on systemizing measurement data from the fjord, so that they can be inserted into models for improving remote sensing of the optically complex water masses. We have also spent a lot of time calibrating central instruments in the laboratory, and published two scientific papers (plus one submitted) based on lab- and in situ-measurements. In the second year of the project we have had two successful field campaigns in May and June 2022. A large bloom of E. huxleyi occurred in Hardangerfjorden in May, and we went on a cruise with the coast guard vessel K/V Tor for a week in the midst of the bloom for a week. This was extremely important for the project, and we are very happy with our data collection from the bloom. In addition, the sky was clear, meaning that we have several good satellite images to work on from the same time period. We also went on a week-long cruise with the research vessel Hans Brattstrøm in mid-June, and collected valuable data from the particularly dark Lurefjorden. The project PhD-student has worked on assessing several atmospheric corrections by using our in situ-measurements as a reference. In October 2022 we went to Vietnam to present results from the EcoSens-project on the largest conference in the community: Ocean Optics. This was very well received, and PI and the PhD-student were invited to be co-authors on a paper in exchange for sharing radiometric data. In addition, we have published a new paper on correction of multiple scattering of light in turbid waters.