Mid-Piacenzian Arctic: Warm Climate & Seasonally Ice-Free Oceans

[Xnn]

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.

 

[SW VandeCarr]

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

 

[Xnn]

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.

 

[SW VandeCarr]

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?

 

[Andre]

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 http://geo1091.tripod.com/.

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.

 

[SW VandeCarr]

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.

 

[Xnn]

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.

 

[Andre]

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

 

[aspergers@40]

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

Xnn; have you seen this interesting site which shows the research papers which show that the Arctic was warmer than today Warmer Arctic In The Past.

Here's PROOF that the sun was hotter during the ice age, with colder oceans Another Problem For Milankovitch: Megaflora of the Ice Age

 

[Xnn]

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 Earth's 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.

 

[aspergers@40]

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.

 

[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.

 

[aspergers@40]

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.

 

[mheslep]

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?

 

[mugaliens]

Ocean and Ice currents are probably a signficant factor.

Hmm... I think you're on to something...

 

[Xnn]

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.

 

[mheslep]

... 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.

 

[Xnn]

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.

 

[mugaliens]

Amazing! About the time we'll run out of oil...

Comming at 'ya!

 

[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?

 

[sylas]

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

 

[mheslep]

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.

 

[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.

 

[mheslep]

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.

 

[Xnn]

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.

 

[sylas]

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.

This is more credible than a projection only, IMO, with the proviso of course that sea ice modeling is hard.

We're going to have to finish up here soon, unfortunately, but it may be worth leaving the thread with a link to [post=2374600]msg #23[/post] of thread "State of the Climate", where mheslep gave a link to the Sea Ice Outlook project at the "Arctic Research Consortium US". This was basically a competition between research groups to predict sea ice change one year in advance. A short term prediction is a rather different beast, subject to larger variations with local effects of wind and current obscuring the trends that are in many ways easier to model: but the failings of the models were intriguing.

In brief; loss of summer ice by 2040 is reasonably well founded; but given the uncertainties it might be rather more, or less, time required.

So, I feel confident that my projection is about the same as that obtained from the physics based models.

Yes, that gives a lot more weight to the projections. I'm sure all the modelers will be continuing to look at the matter and refine their models for some time yet. The one consistent feature of applying physics to the problem is that the loss of ice is not merely an aberration, but a real physically well founded consequence of changes that will be continuing to take place for many years yet.

Cheers -- sylas

 

[hamster143]

I look forward to fishing at the North Pole in July 2040.

 

[Xnn]

Here's an image with a projection drawn using the Cyrosphere data.
It is in rough agreement with Wang's published prediction of 2037.

 

[sylas]

Here's an image with a projection drawn using the Cyrosphere data.
It is in rough agreement with Wang's published prediction of 2037.

Can you be more specific as to what data source you are using? Different groups define the extent in different ways, and the numbers in your graph are not from the definitions I've normally used.

Your graph pretty obviously omits the 2009 figure, which recovered quite a bit from the record minima of 2007/2008, which show up on the graph pretty clearly; but 2009 is not there. Including the data from Sept 2009 makes the match with Wang rather less good... and note also that Wang's group was part of the prediction group I mentioned in the previous post. They underestimated the extent in 2009, as did everyone else; although as usual the number in a given year is in part due to short term changes at the particular weeks of the minimum, not only long term trend. Note that the effort reported must have used different definitions from the numbers in your graph.

Another common source is the http://nsidc.org/news/press/20091005_minimumpr.html (linking to the Oct 2009 report), in which minimum summer extent shows as follows:

(link to full size original)

I wouldn't discount Wang's expectations, but neither would I bet a lot of money on their proposed date. The trend has been substantially faster than estimated in the IPCC 4AR, but Wang's prediction is currently looking to be bit too far the other way.

It's best, I think, to acknowledge that Arctic summer minimum ice extent is hard to predict, and that any specific prediction is tentative, given the limits of models being used. The models do indicate that the decline is real physically founded trend that will be continuing into the future; but quantifying the models to the level of a specific year is... rash.

Cheers -- sylas

 

[Xnn]

I use the UIUC Cryosphere site. Specifically the following diagram (summer):

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

I see they report different values than the NSIDC and don't have a value for 2009.

For 2007, NSIDC reports 4.3 Mkm^2
For 2007, UIUC reports 5.5 Mkm^2

The NSIDC chart shows a decline of about 2.5Mkm^2 over the last 30 years.
The UIUC chart shows a decline of about 3Mkm^2 over the last 30 years.

From the above data, it does not appear that the Arctic would be ice free within 30 years. So, for Wang's and others physics based models to be correct there will have to be an acceleration from the rate of ice loss over the last 30 years.

While the 2009 minimum extent was more than 2007/2008, it does not appear to be substantially greater than the trend line.

The differences between the 2 sources of sea ice extent data suggest to me that they may have different definitions of sea ice.

 

[mspelto]

For Wang and others to be correct we need an amplification. And an amplification does appear to be underway. I was impressed with this paper that I was a peer reviewer for.
http://www.the-cryosphere.net/3/11/2009/tc-3-11-2009.pdf. The emphasis is on observed temperature anomalies and increased heat flux from the open ocean from late summer-early winter.

 

[sylas]

I use the UIUC Cryosphere site. [...]

I see they report different values than the NSIDC and don't have a value for 2009.

For 2007, NSIDC reports 4.3 Mkm^2
For 2007, UIUC reports 5.5 Mkm^2

The NSIDC chart shows a decline of about 2.5Mkm^2 over the last 30 years.
The UIUC chart shows a decline of about 3Mkm^2 over the last 30 years.

From the above data, it does not appear that the Arctic would be ice free within 30 years. So, for Wang's and others physics based models to be correct there will have to be an acceleration from the rate of ice loss over the last 30 years.

While the 2009 minimum extent was more than 2007/2008, it does not appear to be substantially greater than the trend line.

The differences between the 2 sources of sea ice extent data suggest to me that they may have different definitions of sea ice.

I believe the cryosphere today website defines "extent" as the area that has 50% cover or more of ice -- could be 30%, I am not sure. NSIDC uses "extent" as area with 15% cover or more. It may just be me, but I have found it hard to get the information from cryosphere today, by comparison with NSIDC.

I did a bit of private analysis on this last year when the blogosphere suddenly went wild with a bunch of claims about scientific malfeasance based on an exercise by Steve Goddard in the UK counting pixels on images to support some wild accusations. Goddard himself learned from the experience and accepted useful corrections from the NSIDC. But the whole brouhaha did show very clearly just how quick many people are to jump on claims about how climate scientists are all involved in some hoax given even the silliest pretext.

For background on the story, see this poster session on the whole event by Walter N. Meier, Stephanie Renfrow, and Mark Serreze of the NSIDC. ftp://sidads.colorado.edu/pub/ppp/conf_ppp/Meier/Striking_back__A_case_study_in_addressing_a_skeptic_s_public_assertions_about_sea_ice_data.pdf.

For Wang and others to be correct we need an amplification. And an amplification does appear to be underway. I was impressed with this paper that I was a peer reviewer for.
http://www.the-cryosphere.net/3/11/2009/tc-3-11-2009.pdf. The emphasis is on observed temperature anomalies and increased heat flux from the open ocean from late summer-early winter.

Quite right! You can see indications of an acceleration in the data, very roughly around 1996/1997. The acceleration is not quite as strong as Wang's proposal, I think, but some acceleration is a consistent feature nearly all physically based models. The graph I provided from NSIDC has a single regression line from 1978, which if extended as a linear trend would indicate no summer sea ice in the Arctic by the end of the century... but there's an inflection in that graph which would mean any non-linearity makes it likely to be a lot sooner. I wonder if Wang's work relies too much on the 2007/2008 minimum. The abstract states that this minimum is used as a "starting point", but I think the data shows them to be anomalous, even given the accelerating trend.

So... an essentially ice free summer as soon as 2037? Perhaps. This estimate is an average of a number of models, some of which suggest even sooner and others which suggest a bit later. By 2070? Very likely. By 2100? Bet on essentially ice free summers before this. Ice free in this context still allows for isolated floating sea ice and for ice around some coastal margins.

Cheers -- sylas

 

[Bill Illis]

I've spent a bit of time working with the sea ice extent numbers.

The satellite sea ice extent data actually goes back to 1972 but for whatever reason, it has not been matched up/reconcilled to the satellite data starting in 1979 provided by the newer post-1979 satellites.

I've matched up the daily satellite-estimated sea ice extent estimates provided by Jaxa with the Nasa Team algorithm daily data which goes back to 1979. Jaxa used the Nasa team algorithm in developing their algorithm so they are reasonably consistent.

http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm

The main point is that, throughout the year, there is some variation in sea ice extents but there is a seasonal range that has not varied as much as the September minimum numbers make it look.

This chart is not the last word and some adjustments were required to match up the two records, but it does provide a little better perspective on the Arctic/NH sea ice extent. The two lowest sea ice extent years (2007 and 2008) and the two highest sea ice extent years (1980 and 1996) are highlighted as well as 2009 (the red line).

There is still a lot of change required before the day 255 (September 12th, the average date of the minimum) sea ice extent hits Zero.

http://img23.imageshack.us/img23/1255/dailyseidec31.png

 

[sylas]

I've spent a bit of time working with the sea ice extent numbers.

The satellite sea ice extent data actually goes back to 1972 but for whatever reason, it has not been matched up/reconcilled to the satellite data starting in 1979 provided by the newer post-1979 satellites.

I've matched up the daily satellite-estimated sea ice extent estimates provided by Jaxa with the Nasa Team algorithm daily data which goes back to 1979. Jaxa used the Nasa team algorithm in developing their algorithm so they are reasonably consistent.

I think there are problems with your match up, and that you may be giving values for sea ice minima prior to 2002 that are too low. The lack of an existing match up record is very probably because there are all kinds of difficulties with doing a match up across different satellites and time periods, and such a graph is known to be misleading.

Given the rapidly rising temperature records in the Arctic, it is surprising to see bits of the graph dropping below the 2009 minimum. I think this indicates inaccuracies in how you have merged data from different sources.

Cheers -- sylas

 

[Bill Illis]

I think there are problems with your match up, and that you may be giving values for sea ice minima prior to 2002 that are too low. The lack of an existing match up record is very probably because there are all kinds of difficulties with doing a match up across different satellites and time periods, and such a graph is known to be misleading.

Given the rapidly rising temperature records in the Arctic, it is surprising to see bits of the graph dropping below the 2009 minimum. I think this indicates inaccuracies in how you have merged data from different sources.

Cheers -- sylas

Yes, there is some problems in the match-up. The old NasaTeam data has more of a dip at the minimum (compared to Jaxa's algorithm) than the rest of the year. I just left it the way it turned out but another adjustment could have been applied for that. 2009 should be the third lowest year.

The point is when one looks over the whole year seasonal cycle, there is not as much decline as the "one-day" minimum makes it look. There can also be unusual increases in the trends like the 1996 (blue line) shows.

I guess my other point is that the NSIDC or some other entity should spend some time matching up these older records and producing charts like the above so we can have a better understanding.