Heather Tabisola >> Ok, and then Peggy, you are up next.
Peggy Sullivan is going to talk about sonar ice data, telling us a story about the seasonal
ice formation.
All right, let's see.
All right, Peggy, let's see.
Sorry, I have to find you in two spots here.
Ok.
All right, Peggy, you should now be unmuted and then I'm gonna move presenter to you.
Shaun, I'm muting you now.
Peggy, I can't hear you yet.
There we go.
Peggy Sullivan >> There, I unmuted myself.
[Laughs]
Heather Tabisola >> Perfect!
Yeah, I never know how exactly if I'm truly muting people.
Perfect!
Ok.
I'm going to unmute and then you can take it away.
Peggy Sullivan >> All right.
Thank you, Heather.
Good morning, everyone, from all of our remote locations.
I have the benefit of having a sunny window instead of an interior office.
Woo hoo!
I'm going to be talking about Chukchi Sea ice and Chukchi Sea is a marginal ice zone.
So in winter ice cover and open water, all summer, with shoulder seasons are being transitioned
seasons from waves to ice and then from ice to waves.
The Chukchi Sea has just been, has seen really dramatic warming and sea ice changes in the
recent years.
So it's fortuitous for us that we have a long set of data to look at some of these changing
areas.
Next slide.
All right, I'm working on controls.
There it is!
[Laughs] This is the area that we're working on, on
the map.
The seven stars are stations where we've had ice profiler moorings set out and I'm actually
going to be talking and have looked more at the three that I've just circled: C1, C2
and C3, which we call the Icy Cape Line.
That line was located and because of proximity to the Alaskan coastal current and proximity
to Hanna Shoal, which is probably a little further off than the label on the map but
you can kinda get the sense of that.
We do fall deployments and recoveries and so have almost full years of data for each
mooring that we pull back.
We get ice draft as the main data product.
Now, ice draft is very related to ice depth, but what it really is defined as is as the
surface of the water down into the depth of the water it does not account for ice from
the surface, and above.
And it comprises about 90% of the depth, but it actually is draft.
We would have to do further instrumentation with ADCPs to actually get depth.
And we haven't done very much of that.
In addition to the range data that turns into ice draft, we also have temperature and pressure
data.
And at each of these stations we have not only the ice profiler mooring, but also many
other moorings that capture salinity, temperature, and other parameters that we frequently get,
like oxygen and PAR and chlorophyll and nutrients, etc.
C2 location has the longest running data record.
We started putting these out consistently in 2010 and C2 has been out every, well, almost
every year since then.
So, there are nine datasets for C2, four datasets for C3, and seven for C1.
And this table gives you a sense of what I just said.
C2 is the longest running and then the other ones were earlier years and I haven't done
as much with those.
But in sum total we have nine years worth of moorings.
29 year-long datasets and have only lost data from two years of instruments.
So, about a 7% loss and it wasn't really loss of instruments, it was problems with the instruments
themselves.
To the left of the screen, you can see some information about the instrument.
They are from ASL Environmental and they're called IPS5 Upward-looking sonar instruments.
I think we were kind of unique back in this time in that ASL was mostly, if they weren't
deploying their instruments, they were absolutely taking the data, and processing for whomever
was paying for it, and we pushed them to get their software so we could process the data
ourselves and it was kind of a big undertaking.
It's a proprietary MATLAB tool.
It's pretty large and it really takes months to get through a dataset, so we're a bit of
guinea pigs for them, but it's been pretty cool working for the data...er, working with
the data and with them.
This illustration is one of the first cut products that I make when I'm done.
When I finally get from the range, data--raw data--into the ice draft, and this is kind
of an upside-down look, the zero line, there, is the surface and you're seeing the spikes
that go upward are what go into the depths of the water.
Each line of the six-line plot is one week long.
So it gives you a good sense of the variation in how the ice looks underneath the surface,
where you get all the chaos, spiky things, and then you'll get some flat segments that
are actually pancake ice or frazil ice, or thin surface ice between the larger ice events.
Yeah, the stretches of ice.
This is a later product that I make and it actually is a very long-term record.
So you have to remember that these are one-second data points.
So that instruments sitting at the bottom and looking up at the same spot in watching
anything that goes by in every second, it's taking a measurement.
So if you look to the left of this plot with the blue lines, you're starting in mid-November,
to the right, you're ending at late July.
So you're seeing, to the left, some are waves, damping down and then all the chaotic-looking
lines through the middle are a formation of ice and then ice cover through the winter.
And then about three quarters of the way along this plot, you can see a blob there where
the blue is above and below the zero line.
And that is a big wave segment that has come in signifying the break-up of the ice over
the winter.
This has to do, of course, to increased solar insulation, warming, and winds.
And so eventually, it seems kinda like a duel to me, where the winds come in and they fight
with the ice until the winds win and it's open water for the summer.
If you look at the last, I don't know if you can see my mouse here, the last segment of
spiky stuff that goes below zero, that is ice, so it comes after wind.
And this is a really frequent thing we see, and it signifies not ice formation, but ice
coming through with break-up elsewhere in the region.
And then after June 4, you see that above and below zero signal, that is all waves and
open water.
Ice keels are really important.
And when I first started looking at these data, that was one of the main things we were
looking at was how deep can the ice keels be?
And we're trying to answer questions like, is ice gonna come through and destroy the
instrument that we have, as near the bottom as we can?
And at the time, Shell and some of the oil companies were also up there.
And there was some concern about things that they were putting in, and would...
would they be...would prevalence be created by ice coming too deep and hitting things
that were near bottom?
And we're kind of happy to be able to quantify this.
And I have listed here that the deepest keels that we have seen are what, 28.6 and 31.1
meters.
And this is down where instrument depths are between 32 and 40 meters, so it comes fairly
close.
Now, this is not all the time, but it's often enough and enough of a liability that it was
a great thing to report to both researchers who are putting instruments in, but also to
oil companies that where liabilities might exist for putting things in the water.
Um, another thing that I've been looking at with this is seasonal transitions.
So, you have summer open water, winter ice cover, and then you have the transition time,
where you have a chaotic mix of waves and ice coming through.
Generally, in the fall, the transitions are much more orderly.
So you get a strong sense of when things stop and start.
Spring is much more chaotic, with lots of starts to wind and then ice will come back
pretty solidly for awhile and back and forth, back and forth.
I've made this illustration.
If you look at the blue, that's open water for the summer.
The light blue is ice cover, and the red is the transition zone.
And, essentially, it shows this trend of... the transition coming later and later.
The duration of the transition is seasonal, just variability from year to year.
But the transition to or the evolution to this event or this transition happening later
and later every year is pretty obvious.
And very closely, it's correlated with the ice caps, satellite ice concentration data.
Now, I'm looking at my time.
This is just another closeup of some of the snapshot of the data, but it shows you spring
transition.
And even though I just said spring transition is longer and more chaotic, this is a really
fast one that occurred.
And if you notice in the top plot, it's 2.6 day duration.
And so to the left, you're seeing the ice tendrils going down.
And to the right, you're seeing the wave signal.
And zoomed out on the bottom, it goes from the top is a 2.6 day view.
The bottom is a 2.7 hour view of this transition from ice to waves, and I've taken the opportunity
in this plot to show you what ice formation and frazil ice, thin ice looks like.
The tendrils are ice, of course.
There's a wave shown in there in the center, that helped break up the ice.
And then I'm showing you ice keel, which is probably something that came through from
elsewhere, because it's a transition from winter to summer.
And then, to the right of this plot are all waves.
And it is the start of the summer open season.
Then, kind of off on a tangent, but this is something we're looking at right now, with
Catherine Berchok, over at AFSC in the Cetacean and Assessment Ecology Group.
She noticed in some of her walrus data.
So, they've got hydrophones up there that, just a couple of times that, there seem to
be a pattern of having daily, maximum ice signal, followed fairly quickly by a heightened
signal of walrus in the area.
And so we've plotted the daily maximum ice draft.
The walrus data and satellite ice concentration here.
And to do a blow-up of what we're looking at, in April of 2011, the black in, in the
add-on plot there, the black is ice signals, the red is the walrus signal.
And so, there's some conversation and thoughts about going forward about looking at correlation
between the presence of walrus, what the ice looks like, whether there's open ice before
or after the peak in the ice segment and also how the winds might impact all this.
I think I've just covered all that.
And that's it!
So the data analysis and processing are ongoing.
We didn't have data in 2019-20, but we hope to have one going out this summer.
Maybe.
We'll see.
We're working on a paper that will talk about seasonal changes and the wind-ice-polynya
interplay.
Collaboration with Catherine Berchok at AFSC regarding the walrus and...
I actually have a web area that is outside of our Drupal but it's ice profiler and ice
draft plots and it's under EcoFOCI.
So, any questions are welcome and thanks very much for listening.
Heather Tabisola >> Thank you so much, Peggy.