What causes Arctic Sea Ice loss/gain?

Among the commonest anxiety-provoking indicators for Global Warming is the change in Arctic sea ice. Of major concern is a diminution of average Arctic sea ice area and extent over the last few decades: http://nsidc.org/sotc/sea_ice.html

From about 1915-1945, the observed Arctic temperature rose substantially: Observed Arctic Temperature, 1900 to Present - Figures and Tables

During that period, sea ice coverage remained pretty stable: http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seasonal.extent.1900-2007.jpg

Does this suggest that factors beside air temperature are the principal driver for ice loss? Is it the case that secondary (to GW) ocean temperature rise, or perhaps ocean current shifts are the presumed cause of ice loss in current climate modeling?

I ask this as a GQ, but since I have positioned myself elsewhere as an AGW skeptical ignoramus, I am trying to save the moderators their usual chore of moving everything that touches AGW in GQ over to GD. And I assume the factors are open to genuine debate, anyway.

I am not asking this with a secondary intention of debating AGW. I’m asking it in the capacity of an unpersuaded but possibly educable ignoramus.

I didn’t know they had satellites in 1900 measuring sea ice coverage, so I’ll take those figures with a pinch of salt.

The second graph shows that the winter ice has been pretty constant between 15 and 16 M km2, dropping below 15M km2 in the past few years, whereas the summer ice figure has dropped precipitously pretty much continuously since 1970.

This indicates that the primary driver is the sun. Either through increased radiation, or more radiation being trapped via greenhouse gasses such as CO2. This warms the air and the water. Note that some of the Gulf Stream does make it to the Arctic via the North Atlantic Drift, so particularly hot years in the Gulf mean a warmer Gulf Stream which will increase ice loss.

There are a number of measurements prior to the modern/satellite era which might be taken with the same grain, no? :wink:

I did try to stick to reputable sites, as you saw, and not get sucked into the Denier crap.

I am superficially familiar with a little of the research on ocean current shifts, and I’m trying to sort out if that’s considered to be the major driver. “Warming the air” doesn’t help me because my question revolves around why warmer air in the past did not diminish the ice coverage.

As Quartz says, ice and snow energy balances are primarily driven by radiation. Other factors that influence this are air and water temperatures, nighttime cloud cover (reduces emitted IR radiation from the earth’s surface), surface albedo (the fraction of incoming radiation reflected by the surface), ocean and air circulation (advective heat transport), and latent heat flux (heat consumed or released by changes in state - e.g. freeze-thaw, sublimation, evaporation, etc.). There are a lot more factors than just air temperature at work in the arctic.

One thing to note about your first cite is that it shows only annual average air temperatures. Ice dynamics are seasonal, with a summer thaw and winter freeze, and the drivers vary significantly over the course of the year. Annual averages don’t provide enough information to really understand this variation. They can be a general indicator of trends - air temperatures are influenced by the same energy drivers as ice - but it’s a starting point rather than a conclusion.

Quartz, Scandinavian port cities have long records of the extent of Arctic sea ice - greatest and least southern penetration, dates of maxima and minima, etc. It’s not as precise as satellite imagery, but it’s proven to be a decent proxy.

It may just be temperature variance. The global warming signal is very small compared to the year-to-year variance in average temperatures.

In 2007, summer arctic ice sea extent was the lowest ever recorded. This caused a lot of consternation and articles about how global warming was accelerating faster than anyone had imagined. But by January 2008, the sea ice had completely recovered, and the 2008 summer ice was back to historically normal levels. 2009 was also a normal year.

When a couple of years of colder than average temperatures are recorded, global warming supporters are quick to remind us that even if the earth is warming, normal variance can still cause colder than average years. And they’re right. But the reverse is also true - a warmer than average year or even decade is not proof of global warming.

Remember, at the IPCC ‘best estimate’ level for global warming, we’re talking about a signal of about 3.5 degrees per century. The warming in any given year is therefore about .035 degrees - a value that is not even measurable with our current equipment. And the normal temperature variation from year to year is much greater - the global average temperature swings by 2-4 degrees per year - a value about 100 times greater than the global warming signal. Keep that in mind when the inevitable stories come out using annual arctic ice measurements to prove or disprove global warming.

Nowhere in that cite it is mentioned that the graph is based on just satellite figures.

Not in this case.

http://www.ucsusa.org/global_warming/science_and_impacts/science/global-warming-human.html

As the sun actually was/is lowering its activity it is indeed the human influence that remains as the main driver of the warming. Incidentally, remember that we can not ignore the volume/mass of the ice. The denier media loves to mislead people by concentrating only with the surface area of the ice.

As the cites provided show, this is misleading, the ice mass tells the scientists that this is not normal.

And that is why scientists still tell you that the earth is warming.

http://tamino.wordpress.com/2009/06/26/embarrassing-questions/

This is a very odd thing to say when it is thanks to the current equipment that most scientists are telling us that this is an issue. Once again, this is why climatologists concentrate on decadal variations.

When one keeps in mind information that was actually misleading…

Well, when will be the time to demand better from the sources one uses?

Just to clarify - when I agreed that radiation is the primary driver, I’m not discounting anthropogenic effects. Radiation is effected by a whole host of factors, human and other. Greenhouse gases, in particular, have a huge effect on the net radiation at the earth’s surface. Still, the net radiation (including the effects of GHGs) is the single greatest factor in the Arctic ice energy balance.

Please get it into your mind that I am an AGW skeptic, not a denier. Please note that I was specifically including greenhouse gasses, and please note that I made no comment as to the degree of warming due to human influence or lack thereof. I merely noted that CO2 is a greenhouse gas which traps radiation. I do not know if CO2 traps sufficient solar radiation to cause the diminution of the Arctic ice we have seen and I make no statement one way or the other.

I did say that it was the denier media doing this, not you.

But I’m also only saying, there is more evidence that the warming that is caused by humans is causing the diminution of the Arctic Ice.

http://www.pewclimate.org/arctic_qa.cfm#8

http://climateprogress.org/2010/01/06/science-nsidc-warm-greenland-arctic-rotten-ice-multi-year-arctic-oscillation/

I am still a bit confused (sort of my baseline when it comes to AGW modeling) about what is being postulated as the cause for diminished Arctic sea ice in recent decades.

In the temperature graph I cited, Arctic air temps were quite warm–about as warm as the last 30 years–from around 1915-1945, but without a concomitant change in sea ice. Observed Arctic Temperature, 1900 to Present - Figures and Tables
Now that Arctic temps are high again and sea ice is low, I often hear (at least an implicated association) that the high Arctic temps are the cause of the low sea ice.

Is it the case that the high Arctic temps are not the cause, but some other cause related to GW is in play? That’s really what I’m trying to get at. If radiation from greenhouse gases is the mechanism, for instance, are the air temperatures themselves irrelevant? If the high Arctic temps are being proposed as the cause, why did they not cause it during the last cycle they were high?

To explain this one I think we need to remember that it is not just the heat in the air that is the issue for arctic ice, the ocean temperature is important and it is the place the heat is also going into.

As it can be seen from the first graph, the global warming does kick even more around the 90’s, that is also when the arctic temperature goes up in the graph you mention. A good chuck of that ocean global temperature is conspiring* with the air temperature to reduce the arctic ice.

That total heat accumulation was one of the big reasons why scientists were telling us that the earth was still heating up in the previous decade, climate truthers** just ignored this item.

But what if we concentrate just on the local arctic temperatures? There is also evidence that the warming in recent decades was higher than the one around the 1940’s

http://www.sciencemag.org/cgi/content/abstract/325/5945/1236

  • Yes folks, we have a conspiracy in our hands… :smiley:

** (Here I have to clarify that I don’t think you are one, I’m referring to the denier media that is still out there acting like if information like the one just posted does not exist and still continue to mislead many)

As I mentioned in my OP, one obvious answer is a generally warmer ocean. It’s my impression that shift in arctic ocean currents is more typically positioned as a cause than is general ocean warming, which is harder to measure and tends to be applied selectively. For example, the Antarctic sea ice is not diminishing. How much of any Arctic sea ice loss is from natural oscillations in currents and how much is from generally GW-warmed water is not, as far as I know, well-elaborated.

For me as a skeptical ignoramus it’s one of those things where the model explanation is chosen to fit the prejudice: if ice is being lost, it’s increased ocean warmth from AGW (Arctic); if ice is not being lost it’s due to the complexity of ocean currents (Antarctic).

My skepticism would be diminished if the very complex modeling for AGW predicted more accurately what would happen when and where and why (even if the “prediction” predicted past findings, such as a lack of sea ice change in the first half of the 1900s despite Arctic air temp warming). Perhaps that’s coming.

Adjusting a model to explain why something happened after the fact is relatively easy, but not confidence-building.

Nope, What was explained before, different conditions apply down there.

A warmer ocean induces more evaporation that creates precipitation in Antarctica.

That is causing it to increase the volume of Ice inside Antarctica (that is not over the ocean, it is also falling on solid ground) but the ice around Antarctica (over water) did lose volume, the effects canceled out, but that is beginning to change.

What you have there is not much an skeptical argument but a denier one. It is indeed the “They failed to predict the acceleration of ice loss, therefore we should not trust that they are telling us” the problem is that it was acknowledged before that there were less ice loss simulations and data from the antarctic (specially) to make a good prediction.

The main flaw in the argument that we should not be confident in the ice modeling is that it attempts to include that lack of confidence to the more reliable atmospheric ones. But what I see is that even if we grant that most researchers were confident with the ice models, that does not exclude what is being observed.

Instrumental readings now are giving us a better picture of the dynamic loss of ice, and the low unreliable estimations of it turned to be wrong, It would be really silly to then act like if that means that then we should not worry, remember that the IPCC’s ocean rise calculations were based by **removing **the possible accelerated Ice loss as there was not enough data to make more reliable estimations. (Around 1.2 a meter rise of the ocean level was expected by 2100, **without **the water added by an accelerated loss of ice, translation: a higher rice of the oceans is coming)

Concentrating on the point that they where wrong (Many were not, they mentioned that there was not enough data to make a good prediction) regarding the ice loss and attempting then to dismiss the scientists for finding that the ice loss is worse than the acknowledged unreliable expectations, sounds to me like a home owner that expects that because the flames are running faster than expected in a fire storm, that means that the fire fighters were ignorant and that his home is going to be ok, even if the physical evidence says that his home next. I don’t think that is a valid assumption for that homeowner to make.

“(Around 1.2 a meter rise of the ocean level was expected by 2100, without the water added by an accelerated loss of ice, translation: a higher rice of the oceans is coming)”

Missed the edit, that should read: “Around 1/2 a meter rise…”

I think you have confused “sea ice” with total volume of ice contained on the land mass. Antarctic sea ice is stable or increasing slightly. Because it doesn’t get much above freezing at all, the land ice is sort of a balance between precipitation and chunking off into the ocean, but not really a function of air temperatures (until GW drives them above freezing, obviously). See here for a sea ice faq.
"Is wintertime Antarctic sea ice increasing or decreasing?
Wintertime Antarctic sea ice is increasing at a small rate and with substantial natural year-to-year variability in the time series. While Antarctic sea ice reached a near-record-high annual minimum in March 2008, this does not indicate a significant long-term trend."

(Note the hasty reassurance that just because Antarctic sea ice is not melting, we shouldn’t read anything into that. Now if the Arctic sea ice is melting? Hey, take heed.)

I think you are inferring more from the rest of my post than I put there. I’m not denying anything and I guess I’m not aware of the concept of “skeptic” v “denier” arguments. In general it’s my observation that the loss of Arctic sea ice has been attributed to a change in air temperature and that such an attribution does not jibe with what happened 75 years ago. If the attribution is instead shifted to ocean temperatures (current shifts or total warming), that’s fine and even plausible, but to the extent it was not a predicted mechanism suggests that current models are simply adjusted as necessary to account for the observable facts while still maintaining a core belief that AGW must be a correct paradigm, and that where it can’t be made to fit observation, that must be an anomaly.

None of that means the AGW paradigm is wrong. In the mind of this skeptic, though, I’d like to see better predictive strength before I feel like we’ve locked down the science of it.

Again, that is like assuming that the fire fighters were ignorant about the extent and speed of a fire storm, the home owner wondering why that is not locked down to a science is not much relevant when his home will burn next. Being wrong (And again many were not) does not translate to “lets assume it will be ok, because the science is not locked down” that is assuming in the end that we should not worry. However what the data shows is that the ice is going away faster than before.

The point is not that the ice is melting, in the antarctic or the arctic, the point is that it is even less likely now that the seas will rise just to the minimum levels by 2100 that were assumed before.

That is because if ice not melting, not much to worry then about the seas rising, Now if the Antarctic sea ice is melting…

Where will the water go?

I don’t want to belabor the thread much longer, since there is apparently not an answer for my OP, but just wanted to make sure you don’t think melting sea ice raises ocean levels…

I don’t mean to offend; just making sure, since it is a popular misconception.

On the other hand, if flames are licking at the house and we assume the problem is an oil-rag fire in the garagae when it’s a grass fire just outside, we’ve got a problem.

It’s not enough to yell fire because the earth is heating up. It is important to know why because without knowing why we may be taking the wrong action.