Ice Free Arctic

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Main Question or Discussion Point

Here’s a recently published paper on sea surface temperatures 3 million years ago when the Arctic was seasonally ice free:

http://micropress.org/stratigraphy/papers/Stratigraphy_6_4_265-275.pdf

The paper presents some interesting data. The most northern location sampled was found to be 18C warmer during the summer. That's huge! It was found just off the coast of Spitsbergen; a chain of island that was (until a few years ago) encrusted in ice most of the year. In contrast, temperatures at tropical sites were found to be similar to those of today.

They also found evidence of significant warming off the coast of California and western South America compared to less warming further off shore. So, the global warming of that time was not at all uniform.

Note; at the current rate of sea ice retreat and thinning, the Arctic may be seasonally ice free by 2040. As such, this study provides a possible analog for our future climate conditions. CO2 levels during that time period were close or just slightly higher than current levels.

ABSTRACT: The most recent geologic interval characterized by warm temperatures similar to those projected for the end of this century occurred about 3.3 to 3.0 Ma, during the mid-Piacenzian Age of the Pliocene Epoch. Climate reconstructions of this warm period are integral to both understanding past warm climate equilibria and to predicting responses to today’s transient climate. The Arctic Ocean is of particular interest because in this region climate proxies are rare, and climate models struggle to predict climate sensitivity and the response of sea ice. In order to provide the first quantitative climate data from this region during this interval, sea surface temperatures (SST) were estimated from Ocean Drilling Program Sites 907 and 909 in the Nordic Seas and from Site 911 in the Arctic Ocean based on Mg/Ca of Neogloboquadrina pachyderma (sin) and alkenone unsaturation indices. Evidence of much warmer than modern conditions in the Arctic Ocean during the mid-Piacenzian with temperatures as high as 18°C is presented. In addition, SST anomalies (mid-Piacenzian minus modern) increase with latitude across the North Atlantic and into the Arctic, extending and confirming a reduced mid-Piacenzian pole-to-equator temperature gradient. The agreement between proxies and with previously documented qualitative assessments of intense warming in this region corroborate a poleward transport of heat and an at least seasonally ice-free Arctic, conditions that may serve as a possible analog to future climate if the current rate of Arctic sea-ice reduction continues.
 

Answers and Replies

  • #2
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Is it known if the geographic north pole was in approximately in the same location as now 3-3.3 Ma? I know this is too short a time period for significant tectonic activity. However, I'm not sure about stability of the earth's axis of rotation. I know that the poles have several different cycles of movement within a small area but I think the mean location has been fairly stable over the 52 years since the establishment of the US south polar antarctic station.
http://www.aad.gov.au/default.asp?casid=1843
 
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  • #3
Xnn
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The geographic north pole was in the Arctic ocean 3 million years ago.
Plate tectonics move about 1cm/year. So, over 3 million years that equates to 30km or about 20 miles.
 
  • #4
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The geographic north pole was in the Arctic ocean 3 million years ago.
Plate tectonics move about 1cm/year. So, over 3 million years that equates to 30km or about 20 miles.
Thank you, but I acknowledged that it my post. I asked about the location of the geographic pole in terms of the stability of the earth's axis of rotation.. I included a link. The mean location of the geodetic south pole (which is is accessible to daily observation) does move within a circle of about 30 meters radius, but seems to have fairly stable mean location over the past 52 years of observation. My question is: Is it known if a significant shift of the geographic pole is a reasonable possibility over this 3m year period such that the Spitsbergen site could have been at a lower latitude?
 
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  • #5
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There is a mechanism called http://www.nature.com/nature/journal/v452/n7187/full/nature06824.html.

It is legimate physics, when a body is not spinning around a stable axis, which in case of earth can be caused by mass shifts like in the Earth mantle maybe due to dynamic mass changes in mantle plumes due to heat convection. Note that this is not the same as plate tectonics, which is associated with Apparent Polar Wander.

For now I would think that the accuracy of formal claims, mostly based on paleomagnetic construction, could suffer from circular reasoning and uncertaintly in the three dimensional planes of tectonics changing the geomagnetic orientation in a more complex way than assumed.
 
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  • #6
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There is a mechanism called http://www.nature.com/nature/journal/v452/n7187/full/nature06824.html.

It is legimate physics..

For now I would think that the accuracy of formal claims, mostly based on paleomagnetic construction, could suffer from circular reasoning and uncertaintly in the three dimensional planes of tectonics changing the geomagnetic orientation in a more complex way than assumed.
Thanks for the links. The Steinberger abstract describes substantial movement which he attributes to true polar wandering, but still at timescales comparable to tectonic movements.

I just checked the Cryosphere Today site and saw that the 2 Jan,2010 image shows open water north of Spitsbergen. With the exception of the region north of Scandinavia and northwest Russia, the surface extent of the ice pack seems in line with the 30 year average. This region has been historically warm for 80 degrees north latitude due to the Gulf Stream but this is unusual. Current summer temperatures are 5 to 10 C in Spitsbergen so I'm not surprised that they could have been as high as 18 C if the earth was warmer and the Arctic Ocean was ice free 3.3 Mya. Continuous summer daylight lasts about 16 weeks and maximum solar insolation is higher than lower latitudes.

I understand the Pleistocene glaciations began only about 1 Mya although Antarctic ice cap dates from about 20 mya.
 
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  • #7
Xnn
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I just checked the Cryosphere Today site and saw that the 2 Jan,2010 image shows open water north of Spitsbergen.

Wow!

According to the paper, the Spitsbergen sites (909 & 911) were just within the minimum sea ice extent based on 1978 to 1992 averages.

At present, the location of Site 907 is south of the maximum extent of sea ice averaged over the period 1978 through 1992, and the locations of Sites 909 and 911 are
just within the minimum extent of sea ice averaged over the same time period (using Schweitzer 1995)
At the Cryosphere site, I checked some dates from the 1980s and early 90's and it was indeed often iced up to the North of Spitsbergen thru July and August, but not always in January. (I didn't check every year, so maybe I just got lucky)

Anyhow, it seems to be a strange place for sea ice as there can be more ice in the summer than the winter. Ocean and Ice currents are probably a signficant factor.
 
  • #8
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Open water north of Svalbard on 2 Jan is not unusual as can be seen here. Just try more 2 Januaries from the past 7 years
 
  • #10
Xnn
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aspergers@40;

During the Holocene, the earth orbit was such that the NH was closer to the sun during the summer. So, the arctic was warmer around 8000 years ago than it is now. That is in essense the Milankovitch theory. That is that periodic orbital fluctuations drove the ice age glacial max and mins.

Don't see why anybody would consider this is a problem for Milankovitch.

BTW, that site is not a peer reviewed published paper, so it's against forum guidelines.
If you wish to make surprising claims, they really should be backed up by peer reviewed literature.

The earths orbit has been gradually reducing the amount of solar radiation in the Arctic for the last 8000 years. It is expected to continue to reduce arctic solar radiation for another 4000 years. The current warming in the arctic is from rising greenhouse gases and can not be explained by orbital forcings.
 
  • #11
aspergers@40;

During the Holocene, the earth orbit was such that the NH was closer to the sun during the summer. So, the arctic was warmer around 8000 years ago than it is now. That is in essense the Milankovitch theory. That is that periodic orbital fluctuations drove the ice age glacial max and mins.

Don't see why anybody would consider this is a problem for Milankovitch.

BTW, that site is not a peer reviewed published paper, so it's against forum guidelines.
If you wish to make surprising claims, they really should be backed up by peer reviewed literature.
Xnn; I appreciate your reply. Okay, the paper on the twice-size monkey skeletons isn't peer-reviewed, but that shouldn't take away the sensation of their finds. It's a professional university research project with clearly defined data. How can twice-size tree-top monkeys evolve during the pleistocene in the Amazon rainforest? Ans: By the sun being hotter, the trees growing bigger and the fruit growing twice-size. What other explanation is there?

The significance of the finds puts the current topic of an ice-free arctic into the shade. Can you not see the importance of an ice age rainforest twice it's normal interglacial size? Hotter sun, colder oceans is the ONLY explanation imo.
 
  • #12
Skyhunter
Xnn; I appreciate your reply. Okay, the paper on the twice-size monkey skeletons isn't peer-reviewed, but that shouldn't take away the sensation of their finds. It's a professional university research project with clearly defined data. How can twice-size tree-top monkeys evolve during the pleistocene in the Amazon rainforest? Ans: By the sun being hotter, the trees growing bigger and the fruit growing twice-size. What other explanation is there?

The significance of the finds puts the current topic of an ice-free arctic into the shade. Can you not see the importance of an ice age rainforest twice it's normal interglacial size? Hotter sun, colder oceans is the ONLY explanation imo.
There is much better proxy data for solar flux than monkey heads. As well as many other possible explanations for larger monkey heads.

Why would there be colder oceans if the Sun is hotter? That seems counter intuitive. Stronger SW flux would have a strongly positive influence on ocean temperatures.

It appears you are attempting to confirm a belief, not investigate a mystery.
 
  • #13
There is much better proxy data for solar flux than monkey heads. As well as many other possible explanations for larger monkey heads.
Such as what? There are two complete twice-size pleistocene monkey skeletons that still need explaining.
Why would there be colder oceans if the Sun is hotter? That seems counter intuitive. Stronger SW flux would have a strongly positive influence on ocean temperatures.
I'm saying that the oceans get colder due to an increase in deep ocean tidal mixing which lowers the sea surface temperature.
 
  • #14
mheslep
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Note; at the current rate of sea ice retreat and thinning, the Arctic may be seasonally ice free by 2040.
Based on the satellite record since '79? i.e. a 'current rate' measured over what time period, and why that period?
 
  • #15
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Ocean and Ice currents are probably a signficant factor.
Hmm... I think you're on to something...
 
  • #16
Xnn
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Based on the satellite record since '79? i.e. a 'current rate' measured over what time period, and why that period?
The paper in the original post contains the following statement:

At the current rate of sea ice retreat and thinning, the Arctic Ocean may be seasonally ice free by 2040 (Holland et al. 2006a; Comiso et al. 2008; Stroeve et al. 2008;
Wang and Overland 2009).
I have not looked up each of these paper to see how they arrived at 2040. However, I have reviewed the Cyrosphere website and they present a record since 1900:

http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seasonal.extent.1900-2007.jpg

The summer minimum appears to be at an inflection point.
The data points of the last 2 years appear to be below the trend.
However, by simply extending the trend by hand or a 4th order polonomila, I also get a 2040 date. So, the 2040 date appears reasonable.

However, we are sure to hear all types of news reports whenever a new record minimum is reached.
 
  • #17
mheslep
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... However, I have reviewed the Cyrosphere website and they present a record since 1900:

http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seasonal.extent.1900-2007.jpg

The summer minimum appears to be at an inflection point.
The data points of the last 2 years appear to be below the trend.
However, by simply extending the trend by hand or a 4th order polonomila, I also get a 2040 date. So, the 2040 date appears reasonable....
Yes I was looking at the same series. From this hundred year series I take it that you suggest starting the trend around 1970 or later, a subjective choice based on GHG theories I assume. If one looks at the entire 110 year series, takes the data simply as it is, I see a linear decline of ~0.4 million sq km / decade, which would have ice year round in the Arctic for at least another 100 years. No doubt the more recent data is more accurate, but we don't have error margins on this graph.
 
  • #18
Xnn
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I used all the data, and found that a linear trend does not fit very well.

Since 1970 or so, it does appears to be linear with the exception of the last couple years. However, there is no reason I can think of to throw out the last few years.

Excel has a nice function where different types of trend lines and projections can be drawn. So, from just playing around with it, a 4th order polynomial looks to fit the best.
Of course, this isn't a physics based approach, but the data is clearly trending lower at an accelerating rate.
 
  • #19
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Amazing! About the time we'll run out of oil...

Comming at 'ya!
 
  • #20
Skyhunter
Such as what?
Sun spots for recent activity, (last 400 years) and beryllium-10 for further back

There are two complete twice-size pleistocene monkey skeletons that still need explaining.
Be that as it may...it is a huge mistake scientifically to base ones hypothesis on fifth order evidence that is contradicted by first and second order evidence.


I'm saying that the oceans get colder due to an increase in deep ocean tidal mixing which lowers the sea surface temperature.
First. The oceans would not get colder due to tidal mixing, whatever that means. Moving the heat around does not change the overall temperature.

Second. What evidence do you have that suggests such a phenomenon occurs?
 
  • #21
sylas
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Trying to project the data series is not a particularly good guide, no matter what order projection you use, unless you know something more about the underlying relation. You need some kind of physical model for relating ice and climate, and some kind of physically based expectation for what climate might do, before you can really say anything much about when the Arctic might be free of sea ice in summer.

Projections well beyond the range of the dataset are only useful if you have some independent theoretical basis for thinking that the underlying trends follow the kind of function you are using for making the projection.

Cheers -- sylas
 
  • #22
mheslep
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Trying to project the data series is not a particularly good guide, no matter what order projection you use, unless you know something more about the underlying relation. You need some kind of physical model for relating ice and climate, and some kind of physically based expectation for what climate might do, before you can really say anything much about when the Arctic might be free of sea ice in summer.

Projections well beyond the range of the dataset are only useful if you have some independent theoretical basis for thinking that the underlying trends follow the kind of function you are using for making the projection....
Well said. That's why any time we read a prediction somewhere, we would all gain more clarity if the prediction was attached to a "based on the XYZ model/theory" qualifier. Even the popular press could spare a half dozen words to heed that guidance.
 
  • #23
Skyhunter
The Arctic oscillation (AO) has been in an extreme negative phase this winter. High pressure over the Arctic and low pressure in the lower latitudes, leading to an anomalously warm Arctic winter. This has slowed the formation of winter sea ice, however if it persists through winter it could lead to a slight recovery of the sea ice due to a decrease in wind blown perennial ice into warmer waters.

I personally think that as the ice gets thinner and thinner, the Arctic sea ice will disappear suddenly some summer in some not to distant future.
 
  • #24
mheslep
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The Arctic oscillation (AO) has been in an extreme negative phase this winter. High pressure over the Arctic and low pressure in the lower latitudes, leading to an anomalously warm Arctic winter. This has slowed the formation of winter sea ice, however if it persists through winter it could lead to a slight recovery of the sea ice due to a decrease in wind blown perennial ice into warmer waters.

I personally think that as the ice gets thinner and thinner, the Arctic sea ice will disappear suddenly some summer in some not to distant future.
So much for posts 21 and 22.
 
  • #25
Xnn
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Here is an abstract of the 2009 Wang paper that predicts a nearly sea ice free Arctic by September 2037. It is based on 6 IPCC physics based models. Also, the the top quartile prediction is 2028.

September 2008 followed 2007 as the second sequential year with an extreme summer Arctic sea ice extent minimum. Although such a sea ice loss was not indicated until much later in the century in the Intergovernmental Panel on Climate Change 4th Assessment Report, many models show an accelerating decline in the summer minimum sea ice extent during the 21st century. Using the observed 2007/2008 September sea ice extents as a starting point, we predict an expected value for a nearly sea ice free Arctic in September by the year 2037. The first quartile of the distribution for the timing of September sea ice loss will be reached by 2028. Our analysis is based on projections from six IPCC models, selected subject to an observational constraints. Uncertainty in the timing of a sea ice free Arctic in September is determined based on both within‐model contributions from natural variability and between‐model differences.
http://www.agu.org/pubs/crossref/2009/2009GL037820.shtml

I understand that predictions made without a physical model is risky.
A problem is that one might be unwittingly cherry picking the data.
However, when I put the minimum sea ice data from the Cyrosphere site
into an Excel spreadsheet and fit the best curve to it,
I just so happen to get about the same result. So, I feel confident
that my projection is about the same as that obtained from the physics based models.
 

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