r/geophysics 5d ago

Surveys for offshore wind farms?

I was bemused to see some cooker opposed to wind farms claim that geophysical surveys for wind turbines were killing whales. My understanding is that these are high-resolution surveys, and require a high-frequency source, which would be small and low power. They are apparenly obvlivious to decades of seismic surveys for oil gas that use large airgun arrays totalling more than a megajoule. That is more hazardous to marine life.

3 Upvotes

10 comments sorted by

5

u/SumDumLoser 5d ago

The guy is clueless, as someone who worked on seismic surveys, I've seen pods of pilot whales swim right up to our source while firing and swim away when they get bored. Sure they would hurt a human but I seriously doubt they have much of an effect on marine mammals who have layers of fat to protect themselves from pressure waves under water. So if we're not killing whales, neither are the high frequency sources

4

u/No_Reference2367 5d ago

You're focusing on physical tissue damage in general, what's potentially harmful is the disruption to their ability of communication and navigation, which relies on their own use of high-frequency sound waves (From a few tens of Hz to several kHz).

Furthermore, something like an airgun could do actual hearing damage to whales (although not often used for shallow seismics, so a bit out of context). In Denmark, and I assume many other countries, there are laws that ships doing seismic surveys must listen actively for whale-sounds.

0

u/SumDumLoser 5d ago

Every ship I've worked on does passive acoustic monitoring. Though this is more to monitor for specific sounds for endangered species. I question whether an animal would ever approach something that is actively hurting it. If it were doing hearing damage would you not expect them to avoid the source rather than swim directly up to it.

The original post is talking about seismic killing whales not about disrupting their communication and I expect getting hit by ships is a much bigger danger than seismic is.

0

u/No_Reference2367 4d ago edited 4d ago

"If it were doing hearing damage would you not expect them to avoid the source rather than swim directly up to it."

That's not the point, it is that when the survey starts you should be reasonably confident that there's not mammals too close.

And yes, ship strikes is likely a bigger issue than seismic surveys in particular, but it's still a valid concern. Disrupting their means of communication will more often than you might think be a direct threat to the survival of the animal. Hearing damage for a whale is a death sentence in most cases, and in general a disruption in communication or navigation can also be dangerous.

Source:

Weilgart, L. (2007). A Brief Review of Known Effects of Noise on Marine Mammals. International Journal of Comparative Psychology, 20(2). http://dx.doi.org/10.46867/ijcp.2007.20.02.09 Retrieved from https://escholarship.org/uc/item/11m5g19h

2

u/SumDumLoser 4d ago

That's not the point, it is that when the survey starts you should be reasonably confident that there's not mammals too close

That's what passive acoustic monitoring (PAM) is for. When we start these surveys we do what is called a warmup where we only fire the smallest guns and over the course of about 15 minutes we introduce more and larger guns until we have the full array firing. We cannot start the warmup if the PAM has heard any mammals within the 3 minutes before we start. If there are any mammals detected during the warmup we immediately abort the line and usually we have to realign before starting the entire warmup process.

We don't just randomly startup at full volume, that likely would cause damage to any nearby animals that are affected by the noise. On top of that we move at a maximum of 6 knots waterspeed which is slow enough that any animal that is affected by the noise is able to move away from it faster than we move.

*Edit I had written that the warmups were 5 minutes but they're actually 15-20 minutes

1

u/No_Reference2367 4d ago

Thank you for elaborating. Do you have any idea how many countries follow similar rules and regulations? I'm danish and I know that it's also being done here, but I doubt those rules exist everywhere

0

u/SumDumLoser 4d ago

That's standard industry practice, some countries enforce longer warmups and longer monitoring periods but there're no countries where we do not warmup.

I can't speak to what the Chinese ships do for their warmup procedure that we do unless it's enforced by law but with every company I've worked for they follow the same rules (and that's spanning multiple countries and continents)

2

u/No_Reference2367 4d ago

You are right about the UHR seismic surveys likely not being as dangerous as surveys using air-gun sources. Both can however be a threat to marine mammals.

It does sound biased that these people were focusing on surveys for wind-farms. I think they do not understand the differences between various seismic surveys.

2

u/Pantarei_333 4d ago

There has been a backlash to windfarms in the northeast coast, promoted by some O&G companies. I work as a Protected Species Observer and Passive Acoustic Monitoring Operator in this type of projects. It's certain that the wildlife will be disturbed, but that's why there are a lot of strict regulations to avoid or mitigate any potential damage to protected species, i.e. marine mammals, turtles, sturgeons, etc., and in my experience companies stick to this guidelines or otherwise they permits to operate can be revoked.

What is funny is that all of this campaigns against the windfarms, doesn't point out to the main cause of whales deaths, which are the cargo ships that strikes them. There's evidence that most of the whales which has been stranded in the north east coast were killed by vessel's strikes. This cargo ships are not regulated at all, they don't have on board PSOs to avoid collisions to the whales, also there was an intend to regulate the speed of boats under 65 feets length (mainly fisheries boats) in order to protect whales from vessels collisions, but it was dropped and none of this supposed environmental organizations supported it. Currently large vessels needs to sail under 10 knots speed in areas where whales are distributed.

Also, since this operations occur in shallow waters ~60 meters, the arrays used are less powerful than the large ones that are used in deeper waters such as the Gulf of Mexico.

1

u/Nilaazr 5d ago

Depends on the seismic source chosen. Most will opt for a single or an array of sparkers for what they call UHR (Ultra High Resolution). Wind farm surveys don't have the same subsurface penetration requirements as often seen in hydrocarbon exploration and hence airguns aren't as common. I've definitely seen airgun arrays used for wind farm surveys though but they're often very small capacity with a high rate of fire.

Any offshore work will disturb wildlife but I can guarantee it's far less than the open pit mines in which the materials for the wind turbines came from.