Animation Bering Sea

Now that the MODIS white ball in the middle of the Arctic Mosaic is receding more and more, it's high time we start looking at what's going on down below (some of you who weren't hibernating already did of course). As the skies above the Bering Sea and its Strait have been exceptionally clear lately I decided it was a good exercise to get my animation skills in shape for the coming melting season.

Here's what's been happening in the past ten days, from March 5th (day 64) to 14th (day 73):

 

There's obviously a lot of mobility with ice being transported into the Arctic Basin (!). Lots of big leads along the coasts as well. What a difference compared to last year:

I went into the Uni Bremen archives and retrieved images of sea ice concentrations  from the past week. I've put a resized version of the satellite images next to it to see how sea ice concentration images compare to satellite images:

While I was at it, I also retrieved sea ice concentration images from 2004 to this year. It's too bad we don't have satellite images from more previous years, because this is looking exceptionally remarkable, I think.

I think 2011 looks markedly different from recent years, with the exception perhaps of 2007. 2004 and 2005 look more concentrated, but have less ice at the margins that are in contact with the Pacific. The same goes for 2003.

So why is sea ice concentration relatively low and is the ice looking very mobile in this part of the Arctic at this time of year? I have looked at SST anomaly (sea surface temperature) images from this JAXA site, and what the heck, made another animation:

This year the sea surface temperatures seem to be a bit higher on the Pacific side of the Arctic than other years in the period 2006-2010 (again, with perhaps the exception of 2007). SSTs in the period 2003-2005 were higher, which explains why there was less ice on the margins. Of course, in that period the ice was probably healthier than it is now. Who knows how things would look if SSTs were as high now as they were then.

Comments

[Paul Van Egmond]

Compared to the 2010 snapshot, the 2011 ice looks like mush. I can't imagine that it will stand up to the upcoming melt season very well, if at all.

[Gas Glo]

I can imagine it looking more like 2010 day 150
http://rapidfire.sci.gsfc.nasa.gov/subsets/?mosaic=Arctic.2010150.terra.4km

in half that time or even less. I will probably look stupid for saying that come day 112.
Hmm, should I invite a sweepnostake or would it be likely to be too difficult to judge?

[Patrice Monroe Pustavrh]

I have been monitoring ECMWF 850 hpa temp for a couple of days and it looked extremely warm in Bering and Barents sea area.

[fredt34]

Hansen's Surface Temperature Anomaly graph on http://www.columbia.edu/~mhs119/Temperature/RecentT.gif displays an anomaly between 4 and 10°C for February and in recent Dec-Jan-Feb months, in the North area. I guess some warm water enters the Arctic via the Bering Strait now...

[Neven]

But air temps are still freezing right, even if the anomalies are 5-10 degrees C? I don't think this can be having much influence. It must be a combination of warm water and not so thick ice (as before).

And a stupid question: how much sunshine is the Bering Strait area and southwards receiving at the moment? Skie seem to be very clear. Maybe this is also a minor factor.

[Steve Bloom]

Sunrise-sunset is 11:42 in Nome today, which makes sense since it will be exactly 12 hours everywhere at the equinox (although hard to see at the poles). What would be of most interest is to compare daily insolation for now versus later in the season. I'll see if I can find that.

[Steve Bloom]

OK, that was easy. The NASA GISS calculator says 161 (w/m^2) for today at 65N/180, with a range through the month of 108 to 228. For comparison:

December 21st was 3
January 21st was 17
February 21st was 82
March 21st will be 185
April 21st will be 320
May 21st will be 431
June 21st will be 480

[Steve Bloom]

Just to add that these figures are at TOA (top of atmosphere), bearting in mind that clouds or the lack thereof make a huge difference.

[Andrew Xnn]

At the North Pole, the sun should be halfway across the horizon for the entire day.
Further south, the sun will swing from below to above the horizon by equal amounts.

So, while every place will be receiving half a days worth of sun, the intensity of that sunlight will vary widely by latitude. Here is a good paper that integrates insolation over time.

http://www.sciencemag.org/content/313/5786/508.full.pdf

[Patrice Monroe Pustavrh]

Regarding the insolation (avg. per day) at specific location, here is nice resource:
http://aom.giss.nasa.gov/srlocat.html

[Neven]

Thanks a lot for the answer, Steve, Andrew and Patrice.

Insolation must have had some impact as well then, although I'm not qualified to quantify that (and not quantified to qualify it either). All I know is that the last 10 days have been exceptionally clear over a large area, which saved me some time while making the animations (no need to crop these).

[idunno]

Hi Neven,

I was wondering if the Japanese tsunami has had any visible effect on the ice in the Bering Strait.

I am sort of assuming that the ice acts as a big brake on the tsunami, so the effect would be minimised.

Anybody got anything on this?

[JackTaylor]

"if the Japanese tsunami has had any visible effect on the ice in the Bering Strait"
idunno | March 16, 2011 at 11:27

I suspect the Aleutian Island chain absorbed - dampened the energy somewhat as the water flowed north.

Another "blink - comparison - animation" using Uni-Bremen visuals
http://www.polk-nc.com/agw/beringSea20110309.html

[Paul Van Egmond]

Sorry if this was already mentioned somewhere else, but IJIS is back up, with updates up to March 17th.

[Kevin McKinney]

". . . suspect the Aleutian Island chain absorbed - dampened the energy somewhat as the water flowed north."

Just a musician, but the water doesn't "flow." A tsunami is 'just' a wave train; the only displacement in open water is vertical. The slowing (and consequent disruption) of that wave train in shoaling (ie., 'shallowing') water is what causes the heightening of the wave, eventually resulting in a horizontal displacement component being added. I'm sure there's got to be some very interesting physics in the details of how that happens, but as I said, I'm just a musician.

The relevance of all of these considerations to the tsunami impact on the sea ice is that the ice edge is not accompanied by shoaling water, hence the wave doesn't heighten. I suspect the wave 'tries' to continue underneath the ice, but is damped relatively quickly by the resistance of the ice to flexing.

I do wonder how that plays out in physical detail--it seems as if that would also represent an abrupt change in the speed of wave transmission, disrupting the wave train and releasing the energy entrained. I'd expect that there would be some extensive cracking and jostling of the ice along the pack 'front,' but I doubt that there'd be anything very obvious from, say, MODIS's point of view. If you were on the ice yourself, and close enough to the edge of the pack, it might be another story.

Anybody here working from actual knowledge on this topic--unlike me?

Now I'm going to go off and see if I can find out more about this.

[Peter Ellis]

I suspect the wave 'tries' to continue underneath the ice, but is damped relatively quickly by the resistance of the ice to flexing.

For a tsunami in open water, you're talking about a height of a metre or less (probably much less by the time you get to Bering) and a wavelength of hundreds of kilometres. Any "flexing" is going to be absolutely negligible. It would be something more like the entire Chukchi sea rising (and then falling) by a few centimetres relative to the central basin. That's if the wave can propagate through the strait at all: it'll give something very like a single-slit diffraction experiment.

It'd be lovely to know if it showed up in the Cryosat data - maybe it's something they can look at retrospectively once they've got the actual ice data up and running fully :-)

[Peter Ellis]

Also: a note on relative depths. On average, the Arctic ocean is 1.5km deep. To keep things easy, let's pretend the ice is 1.5m on average - a factor of 1:1000. That thin shell of ice won't have any effect whatsoever on the water movements - it's like saying you can stop a cat purring by gluing a Pringle to its head.

On second thoughts, you probably can but only because the poor thing gets confused.

[Kevin McKinney]

Thanks for those considerations, Peter. That clarifies some things.

I was also wrong about something else: there is in fact a horizontal component to the tsunami wave displacement. It's small compared to the vertical term, though (70 m/s compared to 700 km/s), and 'orbital' (ie., back and forth) rather than linear. (Which means I was at least right in my initial comment that the water doesn't "flow," in the sense of a sustained linear motion.)

I haven't found anything on the physics of waves encountering the edge of the sea ice yet, but this is a nice treatment of tsunami basics, clear yet with significant detail (including some basic equations that apply.)

http://tinyurl.com/TsunamiBasics

[logicman]

Just a quick note: NSIDC will be going off-line for a while.
"NSIDC is improving the energy efficiency of our data center! The daily image update will be suspended from Wednesday, 30 March through Sunday, 3 April due to building construction."

Re: tsunami and ice - the energy in a wave causes it to pile up above water where the bottom shoals, as on a beach. I suspect that a wave striking the edge of thick ice will have an impact effect, shoving the ice forward. In the case of thin ice - especially fragmented ice - the wave will penetrate far under the ice as it loses momentum. This can help warm surface water penetrate under the ice.

[Kevin McKinney]

Not much luck with the continued search--perhaps because Peter is right, and the very low ratio of wave height to wave length characterizing a tsunami means that there is very little effect on the ice pack from tsunami waves. There is the following, for those who are interested in technical studies, about normal wave action and the ice edge:

http://europa.agu.org/?view=article&uri=/journals/jc/93JC00653.xml

There is a complication though, and one that Peter alludes to just a bit: the Bering Strait. Depths don't go much below 50 meters, which is enough to cause considerable amplification of wave height and considerable shortening of wave length.

According to the "TsunamiBasics" chapter I linked above, a typical deep water tsunami would have a wave height of around 1 meter (just as Peter says) and a wavelength of around 200 km. When it reaches the continental shelf, with depths more on the order of 200 m, the wave height will be circa 10 meters, while the wave length will decrease to around 30 kilometers. That's a change in ratio from 200,000:1 to 3,000:1.

It would be more than that in the Strait. For coastal water of around 10 m depth, the numbers are: wave height, 25 m; wavelength, 12 km; ratio, 480:1. So we could say that ideally the case for the Strait would lie between the numbers for the continental shelf and very shallow coastal waters. In the real world, it's messier; all kinds of effects that we see in optics apply to tsunami waves also, and create much wider local variance.

(That's why it's so hard to predict what a tsunami will look like when it strikes this or that locality; not all cases have been solved even theoretically, modeling is technically challenging, and much of the seafloor data you'd like to have doesn't exist. See the link for some of the detail.)

So maybe it's possible that there might be some effects in the Strait after all. It's worth noting, though, that in the case of the continental shelf about 50% of the energy is reflected back out to sea. How much gets reflected on the approach to the Strait? I sure don't know.

There's probably some fertile ground in all of this for research by the right investigator. Maybe even using the Cryosat data, as Peter suggested, if the temporal resolution is high enough.

[Peter Ellis]

10m tsunami on the Bering shelf isn't realistic unless the earthquake happens directly there: remember it also drops off with distance from the source.

http://boingboing.net/2011/03/11/japan-pacific-tsunam.html

That's the modelling they put out for the Japan tsunami. Doesn't go into the Arctic Ocean itself, but you get the general picture. The wave's down to about 50cm by the time it gets to the waters around the Aelutians - obviously it'll be higher when it hits the shores of the islands themselves.

The Aelutians have quite a shielding effect, so the deep-water wave beyond them is down to 15cm or so, but rises to ~30cm when it hits the Bering shelf. So, best guess is that in the shallows of the Bering strait, it would have been about 30cm with a wavelength of {something very long} and a period of a few tens of minutes. Easily enough to see on Cryosat, but just not violent enough to damage the ice.

Going back to Pringles on cats, let's glue the Pringle to a thinner area of the cat - its tail, say. Our be-Pringled cat is waving its tail to and fro to the extent of half a millimetre or so over quarter of an hour. Still not going to have a lot of effect :-)

Serious fracturing of the pack comes from wind-driven swells with wavelengths of a few tens of metres - that gives a radius of curvature large enough to stress the ice. On the other hand, they also contain sufficiently little energy that winter ice easily damps them down.

[Peter Ellis]

Easy enough to see on Cryosat assuming Cryosat happened to be overhead at the time, I should say.

[Kevin McKinney]

Thanks once again, Peter. What a purely cool image that link gives!

I'd think idunno's original question and Jack's response are thoroughly answered by now!

[idunno]

Hi all,

There seems to be a developing ozone hole over the Arctic. Climate Central blogged on this on 18 March:

http://climatecentral.org/

I'm unsure what effect this may have on the sea ice. I think it's probably irrelevent to the ice per se, but notable nevertheless...

As regards the tsunami, I'd wonder whether it has perhaps caused the very wide leads at the North of the Bering Sea, but don't know.

It has also sparked the scary thought of what would happen if either a techtonically triggered tsunami, or, worse, a tsunami caused by shelf collapse, were to occur in an ice free Arctic.

We have not had an ice free Arctic ocean for a very long time. I can't remember if it's a time measured in hundreds of thousands or millions of years, but ages anyway. If the Arctic is iced over, it would be impossible for a tsunami to be generated within this ocean. If it is open water, on the other hand...

"Clathrate gun hypothesis". If you Google it, you get something coherent, which is still not available from this quarter.

[Peter Ellis]

1) Ice shelf collapse doesn't cause a tsunami because the ice is already floating. Thus there's no significant water displacement when it cracks off.

2) You can't get a tectonic tsunami either: these occur at convergent plate boundaries only. The boundary in the Arctic is divergent - a continuation of the Mid-Atlantic ridge.

[Peter Ellis]

3) Ice cover is irrelevant. The energies in a tsunami are unimaginable - a mere few metres of ice wouldn't be noticed. See above comments about Pringles glued to cats. Also consider: would a few metres of ice fracture if you drove an articulated lorry over it? Yes. Can a tsunami throw a lorry onto the roof of a house? Yes.

[idunno]

Hi Peter,

I'm aware I'm very close to the edge of my depth here. Referring to your points in order:

1.By shelf collapse I didn't mean "ice shelf collapse", I mean "continental shelf collapse" - that melting of the methane clathrate layer allows a submerged gas field to vent into the ocean, and thus into the atmosphere.

If this begins to happen, seawater flows into the space where the natural gas was previously, potentially causing a tsunami, I believe. Though I will be very happy to hear I'm wrong.

2. Good.

3. Yeah, but... The lorry stops.

The liquid water in a tsunami continues going, carrying the house with it, and picking up the lorry again too, for good measure.

I have also read that the ice has a dampening effect on waves, and that wave action is important in breaking up the ice. If a massive wave were moving underneath an ice sheet, I would expect it to dissipate an awful lot of energy by fracturing ice.

[Peter Ellis]

Re: tsunamis and lorries - that's kind of my point. The maximum energy the ice can "dissipate" is the amount it takes to fracture it - i.e. not quite enough to lift a lorry once. The tsunami can pick up that lorry, slam it down again, roll it over, bounce it round and round and carry it inland for miles. Fracturing the ice wouldn't have any effect whatsoever on "dampening" the tsunami.

The reason a tsunami wouldn't have much effect on the Arctic is not because the ice cover dissipates the energy: it's because the wavelength and frequency are all wrong. The twice-daily tides don't shatter the central pack: a tidal wave wouldn't either, at least in deep water.

If you did get a tsunami in the Arctic (let's pretend it's a convergent boundary, not a divergent one), there would be some shattering at the epicentre where the deep-water wave is highest, but almost no effect on the main pack. However, in a small strip around the edge, where the tsunami rears up as it hits the shore, the ice would be flung around like polystyrene packaging.

Clathrate venting: I see what you mean. From what I read, I think that when geologists talk of "sudden" clathrate venting, they mean a methane release over a period of a decade or so, rather than over millennia. Something like a jacuzzi. Even more like a fart in a bath, come to think of it! For a tsunami, you'd need an energy release over a few seconds to a few minutes, so I don't think clathrate venting itself could cause one.

Maybe it could destabilise an area and set of an underwater landslide? That might cause a tsunami. On the other hand, large landslides need a steep gradient to occur, which isn't really consistent with the wide shallow seas that develop clathrate deposits.

[Gas Glo]

>"Maybe it could destabilise an area and set of an underwater landslide? That might cause a tsunami. On the other hand, large landslides need a steep gradient to occur, which isn't really consistent with the wide shallow seas that develop clathrate deposits. "

Storegga
http://my.opera.com/nielsol/blog/2008/09/24/the-storegga-submarine-landslide-and-tsunami
"Some authors associate the failure of the Storegga Slide with excess pore pressures caused by gas-hydrate dissociation due to sea-level/water-temperature change, other authors consider that the Storegga Slide may have been triggered by offshore earthquakes."

[Gas Glo]

Even if the steep gradient needed isn't really consistent with seas that develop clathrate deposits, I would be more concerned with gas-hydrate dissociation in the large areas the tsunami hits rather than the gas-hydrates at the source of the landslide if such a landslide struck in the Arctic Ocean. Of course, if they are less frequent than once per 60,000 years maybe we don't have to worry too much about that scale of landslide.

[idunno]

Hi Peter,

Yeah, I mean an underwater land-slide, or perhaps an underwater water-slide, and I believe that underwater features consistent with the debris from one have been discovered in several locations around the world. I seem to remember there are several such features in the Gulf of Mexico, for example.

What I understand may potentially happen as a continental shelf such as the East Siberian gets warmer is this:

The methane clathrates are eroded over a period of years or decades, releasing a significant quantity of methane, and leaving behind a seabed that is now composed of liquid mud sediment, instead of the methane clathrate which was very solid.

As this whole thing is eroded away, there is a danger that it will uncap a whole gasfield. Quite what there is down there is relatively unknown, and some of what is known is probably commercially confidential.

As the seabed is composed of sedimentary deposits of all of the silt, and associated organic matter, carried Northwards by rivers in Siberia and Canada over several million years, there is possibly a lot of gaseous methane down there. I have read a huge range of figures, from 30% of known methane reserves to 300% of known methane reserves. Unknown unknown amounts.

Should a gas field of significant size suddenly vent, seawater will rush in to take its place, and God/Gaia/gravity (delete as appropriate) help us, cause a tsunami by itself, even assuming that the methane doesn't explode as and when it surfaces.

Looking at the geological-scale reconstructions of atmospheric methane levels, it does seem that methane has often been released in great sudden spurts, to dissipate slowly over time afterwards. So the graph looks like a sawblade.

In the worst case scenario, the tsunami and/or methane explosion trigger further gasfield ruptures, and so on, up to the point where it is not the ocean that becomes anoxic, as in the recent BP Gulf disaster, but the atmosphere which becomes anoxic, as in the extinction event of 251 million years ago; which wiped out 96% of known species and after which the planet did not return to a state with an atmosphere capable of supporting oxygen-dependent species for 50 million years.

"Global warming is a mutual suicide pact" - or words to that effect, Ban Ki Moon, 2011.

[Neven]

There currently is a bit of a hot spot over the Bering Sea area, with an anomaly of 15-20 degrees C. 'Cold' Bay in Alaska is reporting +4 degrees.

BTW, I have experimented with the first animation by embedding a Picasa slideshow. This way the animation can be stopped, and you can move forward and backward between frames. I have to try out a few things, but I think it's better than those looping GIF animations.

[Greg Wellman]

Neven, you might want to fix the link(s) in your comment above mine. I think you left out the closing quote mark in the url of the first link, causing Firefox (at least) great problems.

[Neven]

Thanks, Greg, link is fixed!

[Clare]

Further to idunno above who commented re. the Arctic ozone hole "I'm unsure what effect this may have on the sea ice. I think it's probably irrelevent to the ice per se, but notable nevertheless..."

I realise this is slightly aside to most of the discussion here but I was fascinated to hear a presentation by Kathryn Lister of this research at the 2009 NZ Antarctica conference, to see how much the cell damage increased when the ozone hole passed overhead cf. the embroyos just in open water (with the control sample underneath the sea ice).

"The Antarctic 'ozone hole' combined with no sea ice causes severe oxidative damage in echinoid embryos"

http://precedings.nature.com/documents/2906/version/1

.." The presence of the ozone hole, and a corresponding increase in UV-B exposure, resulted in unequivocal increases in oxidative damage to lipids and proteins, and developmental abnormality in embryos of S. neumayeri growing in open waters. Results also indicate that embryos have only a limited capacity to increase the activities of protective antioxidant enzymes, but not to levels sufficient to prevent severe oxidative damage from occurring. Importantly, results show that the effect of the ozone hole is largely mitigated by sea ice coverage. The present findings suggest that the coincidence of reduced stratospheric ozone and a reduction in sea ice coverage may produce a situation in which significant damage to Antarctic marine ecosystems may occur."

Probabaly you are already well aware of this ability of sea ice to filter out the UV-B, in which case ignore me. But any increase in ozone hole over the Arctic has all sorts of implications for the food chain there too. As already has been mentioned there is the disruption to the timing of algal blooms and also with sea ice loss I presume a loss of substrate (not sure this is the correct term in this context?!) for the algae on the underside of the sea ice and all organisms in that habitat?

Clare, whose uni biology was obviously some years ago!

[idunno]

Hi Clare,

Idunno, whose uni biology was obviously some decades ago, (and a small portion of a wider course)...

In that case I think there probably is some possible impact on the sea ice, as the presence or absence of algal blooms could have a large effect on the albedo, and there is some new research suggesting that some Arctic algae exude a natural antifreeze.

Whether your research indicates that the impact will be on the algae or the krill, and therefore will increase or decrease albedo, I dunno.

Anybody interested would find a good discussion of the plankton cycle at:

http://worldoceanreview.com/en/

...within Chapter 5.

I suppose there is also a follow-up question... If the ozone layer can affect the sea ice, can the sea ice affect the ozone layer?

Can the presence or absence of sea-ice contribute to the erosion of the ozone layer? Haven't the foggiest... Anybody?

[Gas Glo]

[Quote]I can imagine it looking more like 2010 day 150
http://rapidfire.sci.gsfc.nasa.gov/subsets/?mosaic=Arctic.2010150.terra.4km

in half that time or even less. I will probably look stupid for saying that come day 112.
Hmm, should I invite a sweepnostake or would it be likely to be too difficult to judge?
[/Quote]

Time to do the verification - yep I'm looking stupid.

There has been little fall in area per
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/recent365.anom.region.2.html

I was probably just getting too concerned about what was merely weather variations.

[Neven]

Gas Glo, it is always a healthy thing to call oneself stupid every once in a while.

But let's wait till day 150 of this year and see how stupid you really are ;-), because I don't think the differences right now are that huge, when eyeballing MODIS images. It's too bad we don't see more of the Northern Pacific though.

[Neven]

Over on the Wetterzentrale forum I read this:

...APRIL 2011 YEAR GROUP AND EARLY SUMMER ICE OUTLOOK...

THE YEAR GROUP FOR APRIL IS 1989. THERE ARE A FEW IMPORTANT DIFFERENCES BETWEEN THE ICE AT THE FIRST OF APRIL 2011 AND THE FIRST OF APRIL 1989. FIRST...THE SHOREFAST ICE ALONG THE WEST COAST ISSIGNIFICANTLY LESS THIS YEAR THAN IN 1989. DURING THE WINTER OF 2011 SEVERAL STRONG LOWS MOVED NORTH ACROSS THE BERING SEA. THIS UNUSUAL TRACK OF LOWS BROUGHT OFF SHORE WINDS THAT PREVENTED THE SHOREFAST ICE DEVELOPING TO NORMAL EXTENTS. SECOND...THERE IS THICKER ICE IN THE BERING SEA AT THE START OF APRIL 2011 THAN IN 1989. THIRD...IN2011 OFF THE NORTHWEST ALASKA COAST IN THE CHUKCHI SEA THERE IS A
SIGNIFICANT AMOUNT OF MULTI YEAR ICE. OUR OBSERVATION TOOLS ARE BETTER TODAY THAN THEY WERE IN 1989 AND THE RECORDS FROM 1989 ARE LIMITED. THIS MULTI YEAR ICE WILL IMPACT THE OPENING OF THE CHUKCHI SEA AND THE NORTHERN ALASKA COAST.

National Weather Service, Anchorage Forecast Office Marine Weather

---

Unfortunately I can't find a direct link.