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Day 9 - Physical Oceanographer Zhaoru Zhang

Updated: Dec 3, 2021

Hi, This is Zhaoru Zhang, a physical oceanographer working on coastal dynamics and polar oceanography. This is my first open ocean cruise, and it is so nice that we came all the way to the subArctic regions in the Norwegian Sea, with my SJTU colleagues and scientists/artists from six other countries (Norway, Scotland, Spain, Portugal, France, Finland) participated in the joint Norwegian-Chinese project Stressor.

The focus of this cruise is on the aggregation of Calanus finmarchicus, an important species of zooplankton that support the fishing ground in the Norwegian Sea. Our objective is to reveal the locations of the C. finmarchicusassemblages and to find out the coupled physical-biogeochemical processes that are responsible for the assemblages.

In this cruise I mainly work with the moving vessel profiler (MVP), which is an towed, undulated vehicle equipped with a AML-CTD, a fluorescence sensor to measure Chlorophyll concentration, and a Laser Optical Plankton Counter (LOPC) to measure the zooplankton abundance. I have been working with a similar vehicle called Acrobat for coastal oceans in China. These towed vehicles equipped with different sensors are really nice in that they could provide high-resolution profiles of hydrography and biogeochemical properties, from which mesoscale and submesoscale features such as fronts, jets and internal waves as well as their relations to biological features can be well resolved.

A few days ago I gave a presentation in the daily cruise meeting, which was about our cruise in the Yangtze River estuary and our findings based on the Acrobat measurements. People showed large interests and there were fruitful discussions on the different coastal ecosystems in a mid-latitude estuary environment and in a subpolar environment.

Up until now we have surveyed 8 transects with the MVP, which clearly showed a density front between the Norwegian coastal water and the warm Atlantic water near the shelf break, as well as a jet in the frontal location. These mesoscale features are quite closely coupled with the phytoplankton aggregation. The weather could change a lot during one transect, from sunny to cloudy to windy to snowy and even hails, so really small scale processes.

The work of my SJTU colleagues in this cruise cover CTD cast operations, ADCP/LADCP setup and data processing, LISST/LOPC setup and data processing, EK 60 data processing, water sample collection and filtration for future analysis of nutrients, primary production, particulate organic carbon, biosilicon, biological respiration and gut fluorescence. We also have an underway system to measure the O2/Ar ratio for getting the information of net community productivity. Ziyuan and Huizi sent us the Lagrangian Coherent Structure images every day, which provides very useful information for the chief scientist to determine the cruise route for the next day. We always love the areas with mesoscale eddies and meanders that favor active onshore-offshore mass transports. The SJTU team has been working closely and smoothly with the Norwegian team including scientists, technicians, artists and crew members to recover the secrets of the lovely creatures – Calanus finmarchicus!

Today we went into the fjords of the Lofoten Islands, which has one of the world’s best views. Tomorrow we’ll get on land for a couple of hours to look around the town Svolvaer. The students can’t wait for this! Yiwu will stay on the ship to introduce SJTU and the collaborated project to local middle school teachers, students and artists, as an outreach activity planned for this cruise. Many thanks to Yiwu! We promised to bring good snacks for her.

Best wishes for the rest of the cruise, and there are things to expect every day!

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