Pack Ice, MIZ and the sonar model

[Ghost Dog]

I havent done alot testing, but does being under the pack ice or in a marginal ice zone have any effect on sonar?

Under the ice, the ambient sound should be very low. Unless its spring when the the pack ice thaws and begins to break up.

In a Marginal Ice Zone, where large floes and icebergs smash into each other, the ambient noise levels should be very high, making above layer detection rather tough.

Does DW model this in any way? If not, is the sound model capable of modelling this in future releases?

[The Bandit]

Shouldn't the under ice zone work almost like a convergence zone, since sound would be reflected back down by the ice?

[Ghost Dog]

Mostly, but large keels would cause bouncebacks or block the sound in some cases. the low salinity of arctic water would also affect the thermocline and sound propagation.

The main factor, as I already mentioned is the low ambient noise. its dead quiet under the ice, making other sounds stand out. The low temperature also means that deep sound channels would form in the deeper parts of the arctic ocean.


Like bandit mentioned, ice is highly reflective to sound, but its irregular contour would produce unpredictable bounces.

[Bellman]

Well Kapitain is our 'iceman' so when he surfaces from his friday night out 'dive' I am sure he wont be bashfull
in enlightening us about his experiences.

[Kapitan]

right ice flow

yes it does affect your sonar both active and passive to a point, your towed array becomes less sensative due to the colder waters when your nearer the ice say 30 meters or there abouts (hence why my towed isnt streamed most of the time)

the ice makes a loud noise very loud but it can be filterd its harder to filet on the russian subs than americans, but your sonar can pick up things that are not there.

if you go deep your sonar should work as per normal, however running shallow under ice does lead to some deteriaration in the quality of detection.

pack ice is one hell of a pig it moves constantly and therefore is hard to avoid its even modeled in dw the ice does move.
the pack ice can be dodged but you realy need to be on the move all the time

find a decent sized hole in the ice and surface there. but if you want my advice dont surface at all unless need be do everything in your power to stay below it cause it makes it alot better and you dont run the risk of damaging sensative equipment or the sub

[Kapitan]

its dead quiet under the ice

hell no ! all year round the ice is always moving winter to summer always shifting always breaking always filling gaps and the noise is very high under the ice.

you wouldnt think so but it is, theres a guy on HMS Tireless i know a good friend he is sonar oparator he came back from ICEEX04 or 05 cant remember and he said that it was like listning to cars crashing into walls all day long.

thats put me off being sonar oparator



there are thermo's but the closer to the ice you are the better but you also put yourself in a bad situation as your sensor's cant realy pick up enamys that well, i stay between 30 and 50 meters at 3 to 6 knots only if tracking do i excead that and only if i know i wont be detected.

4 months ago i trailed a chinease Xia SSBN under ice at 12 knots for 11 hours no problem untill she went shallow real shallow 25 meters i almost lost her at one point because the ice was making a racket that it was covering the other subs noise, the Xia is pretty loud on its own it was only because she went to 200 meters i caught her again.

colder the water the less the sound travels or is it the hotter the water oh crap i forgot

Like bandit mentioned, ice is highly reflective to sound, but its irregular contour would produce unpredictable bounces

.

yes it would it would be like shining a light or laser onto a very broken mirror the rays would go every where and thus breaking up and masking the sound another reason why i travel shallow.

[Sub Sailor]

I have made three trips North back in the 60s and it was noisy all the time. Dam ice grinds and all kind of stuff, I don't know how the Sonar guys put up with it.
Also you have to watch for the ice heaves that will push some the ice down, they said it because other ice rides up over it. It can be really hard to find the "polynaya" (I think it at least close in spelling)
The scientist that were with us say it is never still always drifting around, I am still not sure how the sonar people find another sub under there. On the trips we made we never encountered any at least that we knew about.
Never going to make it as a tourist attraction that's for sure.
Supposedly the Russians were or are really good at under ice operation and we believed they could launch missiles from up North. I don't know bcause the times we surfaced there was alway ice all over the decks where missles tubes would be. Most of the time just the sail would get through. Anyway we never had to find out.
There is a young man on the site who really knows about the ice, wrote a great treaties on it, recommend you read it.

Have a good one,

Ron Banks MMCM(SS), USN(Ret)

[Kapitan]

russian missiles launched from 50 meters will get through ice upto 2 meters thick i have no clue how they do it but i think its to do with the gas they use to eject the missile

also the typhoon is so large that the ice you saw riding on your deck would probly only be about 1/4 the way down the hull on a phoon

the phoons hatches are very strong and can break ice the sail is designed for under ice in the first place it cuts it first then cracks the rest of the ice around it and thus making it easier to open hatch and fire theres a video on it some where when i can find it

read my under ice guide that will give you a good idea too its on the subguru downloads page

[Sub Sailor]

Kapitan:
Thanks for the info and it makes sense about the size of the Typhoon, hadn't thought of that. I always went North on a Attack Boat.
I have your paper on under ice operations and wrote you at the time how good I believe it is. Very good reading

Thank you,

Ron Banks MMCM(SS), USN(Ret)

[Kapitan]

thanks sub sailor and i think your in the VMC also?