Weather, and Wind, and Waves! Oh my!
By Karen Douglas and Martin Scherwath
While the study of storms is interesting to many, those of us on the R/V Thompson
prefer to investigate our study areas when the wind is in the 0-20 knot range. Nasty weather is triply bad because (1) not only is it hard on those who have to find their sea-legs on the ship and get used to being thrown back and forth while trying to work but also (2) for ROV operations, which have a certain threshold beyond which people and equipment are outside their safety zone, and finally (3) the work schedule has to be constantly adjusted in order to account for the weather so that it becomes difficult to plan coordinated operations with shore support.
The Waiting Game
We spent some time in Trevor Channel, off the coast of Diana Island and Bamfield, evading bad weather and taking the opportunity to pick up some spare parts. We are now waiting at Endeavour for the weather to calm, as we continue to make preparations for the upcoming dives on deck. Everything is tied down including buckets, chairs and milk crates. Those still working in their chairs narrowly missed being tied down themselves. The crew is in good spirits but unfortunately this weather puts a bit of a damper on our plans.
To Dive, or Not to Dive
Our highly reputable ROV partner, ROPOS, operates happily in wind speeds up to ~25 knots (46 km/h) under the condition that the sea state is not worse than typical for this wind speed (wave height approx. 3 m). Lower thresholds come into play when ROPOS is required to carry payloads such as instrument platforms or ROCLS, the Remotely Operated Cable Laying System. This upper threshold wind speed of 25 knots corresponds to a 6 on the Beaufort Scale, called a "strong breeze"; slightly stronger winds are called "gales", a 7 on the Beaufort Scale. Other ROVs often have limits in the lower 20 knots. However, ROPOS can draw on their considerable crew experience and the fact that the most critical operations, launch and recovery, are performed using their LARS (Launch And Recovery System) crane which is self-stabilizing and extremely reliable.
For this cruise, ROPOS thresholds are not coming into play for some crucial cruise operations. One example is our deep-sea mooring installation, which required flat seas. See our mooring magic blog post for details.
Some statistics regarding this cruise: We planned a total of 59 cruise operations, including 21 ROPOS dives. Here's a summary of the weather requirements:
| Number |
Type |
Weather Required |
Example |
|---|---|---|---|
| 4 |
deck operation |
very good weather and daylight | deploy mooring |
| 2 |
deck operation |
good weather | deploy ROCLS |
| 2 |
ROPOS dive |
good weather and daylight |
connect L-box |
| 6 |
ROPOS dive |
good weather |
recover ROCLS |
| 6 |
ROPOS dive |
medium weather |
deploy Wally |
| 7 |
ROPOS dive |
no special weather requirements |
install short-period seismometer |
If only we could synch our schedule with Mother Nature!
NEPTUNE Canada vs the Pacific’s Weather
While waiting out the weather in Trevor Channel, we busily prepared POD 3 for redeployment at Barkley Canyon, which was a success. The sonar was affixed and the camera was removed as the new one has its own little tripod. We’ve also been tying up the cable (or “juting” as we call it here) with twine which becomes difficult when the fibres are blowing off and the twine won’t go anywhere voluntarily except horizontally into your face, but we’re managing. Our wait at Endeavour continues and we are building cables and preparing instruments. So, when this tempest finally blows past, we’ll be ready to go!
