Blog entry by Lisa Skein
By the time you read this we would have passed the halfway mark of JC237! It genuinely feels like time is flying and I can’t believe we only have about two weeks left at sea. Seeing as we’ve come to this stage of the expedition, I thought it would be good to provide a quick recap on what we’ve achieved thus far.
So far, we’ve completed 12 ROV dives, 11 AUV missions, 18 deep water CTD casts, 70 push-cores (taken via ROV), 10 gravity cores, and 4 mega-cores. This is great progress and we have already collected an incredible amount of data that’s teaching us a lot more about the Whittard Canyon system and all of its complexities! As with any fieldwork, we have also been faced with a few obstacles including a couple of very “cloudy” ROV dives, an AUV that got a bit scared when she came too close to the seabed, and a RoCSI eDNA sampler that needed a few small upgrades. I’m happy to report that almost all of these problems have been solved, apart from the bad visibility during a couple of ROV dives that is unfortunately not within our control but in the hands of mother nature!
The most recently completed ROV dive has been particularly exciting for our geologists on board as they were able collect rock samples from the seabed using a rock drill! As we do our best to get the most out of each dive, we also collected biological samples and more visual survey information. Much of this will be used to establish how accurate statistical models have been in predicting where certain habitats and species are likely to be found, and to help improve the accuracy of future predictions these models will make.
Improving deep sea maps
As I’m writing this, the RRS James Cook is stationed above the Eastern Canyon of the Whittard Canyon system and the ROV is performing a multibeam sonar survey of the Acesta wall we’ve written about in an earlier article. Multibeam sonar is an acoustic mapping technique used by ships to perform geological surveys of the seafloor. Usually, multibeam echosounders (the devices used to perform the surveys) are hull-mounted on ships and are therefore downward-looking. This set-up is perfectly fine for constructing seabed maps that reveal the depths at which major geological features are distributed. It cannot, however, provide good resolution of vertical structures such as overhanging cliffs, caves, terraces and gullies (features that are often found in submarine canyons). Indeed, we’ve observed some very dramatic and unexpected geological features during ROV dives on this expedition; features that were not obvious from current bathymetric maps produced by downward-looking sonar.
In addition to the valuable imagery and physical samples we get from deep sea vehicles like ROVs and AUVs, these vehicles also present new opportunities for seabed mapping. To accompany the traditional downward-looking sonar used by ships, scientists have recently started to use these underwater vehicles to perform mapping surveys of vertical features. This is done by modifying the orientation of multibeam echosounders in a sideways-looking direction, as opposed to the traditional downward-looking approach. This technique has been immensely informative in revealing intricate features of marine habitats, especially in submarine canyons.
A very special birthday
In the meantime, I’ve just spent my very first birthday at sea! It’s been truly special and I’ve been spoilt with cake, chocolates and special cruise memorabilia. To end off the day, the ROV team had a last surprise in store for me: potentially the world’s deepest birthday card! (See below). A heartfelt thank you to everyone on JC237 (and especially the night shift team) for making this a birthday I’ll remember forever.