Antarctic sea ice, ha ha ha!

Some seem to find it somewhat amusing that an icebreaker full of journalists is currently stuck in the Antarctic sea ice, awaiting rescue (yes, Andrew Neil, I’m talking about you). To be fair, I can see the irony (a little) but it does seem a bit insensitive (I’m sure they’ll be rescued, but it can’t be all that pleasant) and indicates an element of scientific ignorance. I often think that if people want to learn more about sea ice, they should probably just go to Neven’s Arctic Sea Ice Page. It seems to be one of the best resources on this particular topic. I thought, however, that I might try and put the Antarctic sea ice issue into some kind of perspective.

The National Snow and Ice Data Center has a page dedicated to Arctic vs Antarctic sea ice. It has figures showing the Arctic and Antarctic sea ice extent since 1978 (below). I appreciate that these figure only extend to 2007, but the long-term Arctic sea ice trend (1978-2008) is a loss of 500000km2 per decade. For the Antarctic it is an increase of 100000km2 per decade. So, the long term Arctic sea ice extent trend is 5 times greater (and negative) than the long-term Antarctic sea ice trend (positive).

Total Arctic sea ice extent 1978-2007 (credit : NSIDC)

Total Arctic sea ice extent 1978-2007 (credit : NSIDC)


Total Antarctic sea ice extent 1978-2007 (credit : NSIDC)

Total Antarctic sea ice extent 1978-2007 (credit : NSIDC)


One should also recognise that an increased Antarctic sea extent has very little influence on albedo (it’s the Southern winter) while a reduced Arctic sea ice extent – in the Northern summer – can have an effect on albedo. The above figures also only consider sea ice extent/area, rather than mass/volume. The Polar Science Center also gives data for Arctic sea ice volume. This is shown in the figure below and shows a very obvious, and continuing, decrease in Arctic sea ice volume/mass.
Arctic sea ice volume anomalies computed (for each day) relative to the 1979-2011 average for each day. (credit : Polar Science Centre)

Arctic sea ice volume anomalies computed (for each day) relative to the 1979-2011 average for each day. (credit : Polar Science Centre)


If one wants to consider the influence of global warming, one should also consider both sea ice and land ice (i.e., ice sheets). The figure below is from the IMBIE experiment and shows that both Antartica and Greenland have been losing mass (H/T to Tamsin Edwards for this link). In fact, one can go further and search Google Scholar for recent papers on Antarctic sea ice trends and one would find a recent paper (Bintanja et al. 2013) which says

Specifically, we present observations indicating that melt water from Antarctica’s ice shelves accumulates in a cool and fresh surface layer that shields the surface ocean from the warmer deeper waters that are melting the ice shelves. Simulating these processes in a coupled climate model we find that cool and fresh surface water from ice-shelf melt indeed leads to expanding sea ice in austral autumn and winter. This powerful negative feedback counteracts Southern Hemispheric atmospheric warming. Although changes in atmospheric dynamics most likely govern regional sea-ice trends4, our analyses indicate that the overall sea-ice trend is dominated by increased ice-shelf melt.

So, the increase in Antarctic sea ice extent could be due to the accumulation of cold water from the melting Antarctic ice sheets. Admittedly, there are other papers (Swart & Fyfe 2013) that suggest that the fresh meltwater is having little effect, and that the Antarctic sea ice trend is simply consistent with natural variability. Either way, there appears to be little evidence that an increased Antarctic sea ice extent has any particular significance with respect to global warming.

Antarctic and Greenland mass changes (credit : IMBIE)

Antarctic and Greenland mass changes (credit : IMBIE)


So, yes maybe it is a little ironic that a high-profile Antarctic expedition is stuck in the Antarctic sea ice. However, a ship stuck in the Antarctic sea ice is not all the surprising and doesn’t really imply anything with respect to global warming/climate change. The increased Antarctic sea ice extent doesn’t really cancel the reduction in Arctic sea ice extent/volume (the long-term rate of decrease of Arctic sea ice is at least 5 times faster than the rate of increase of Antarctic sea ice). The Arctic sea ice continues to lose mass as do Greenland and Antarctica. Whether it is slightly amusing that a ship is stuck in the Antarctic sea ice or not, I hope everyone on board is safe and well and that they’re rescued soon (as I’m sure they will be).

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91 Responses to Antarctic sea ice, ha ha ha!

  1. Victor Venema says:

    Talking about ironic. Only 5 posts since you announced to stop blogging during the holidays. 🙂

    Happy new year everyone!

  2. Victor, that was meant to only apply to Christmas. I was impressed that I managed not to write any posts from the 23rd till the 26th 🙂 My forthcoming travels are likely to curtail blogging for the next few weeks though.

  3. Jabba, true they are more up to date. Don’t think it changes much though. The long term Arctic sea ice extent trend is still, I believe, quite a bit bigger than the long term Antarctic sea ice extent trend.

  4. Kevin says:

    Hi Anders,

    A few random thoughts:

    [1] It’s not just journalists on the Shokalskiy – scientists, too. More here: http://www.spiritofmawson.com/

    [2] I’m not sure what you mean by the comment on hemispheres, albedo, and seasons? Southern Hemisphere sea ice is increasing across all seasons, including the austral summer (southern hemisphere sea ice minimum), e.g. http://nsidc.org/arcticseaicenews/files/2013/12/Figure4b.png

    [3] The trends are interesting from the point of view of understanding climate processes at high latitudes in the southern hemisphere. In addition to the aggregate trend, there are interesting spatial patterns (http://nsidc.org/data/seaice_index/images/s_trnd_hires.png), and — as you say — questions about what processes are responsible (melt water, winds, ozone, etc), especially in light of CMIP5 simulations (IPCC AR5 WG1 draft, Figures 9.24 and 10.16, plus FAQ 4.2 Figure 1 is pretty cool too)

    cheers,
    Kevin

  5. johnrussell40 says:

    You say, “a reduced Arctic sea ice extent – in the Northern summer – can have an effect on albedo”. I’d say “a major effect on albedo”, though if you want to play it safe, “a significant effect”, will do. I say this partly because, according to http://tamino.wordpress.com/2012/10/01/sea-ice-insolation/ , “…at the point of midsummer, the poles receive more solar energy than any other place on earth”.

    My take is that due to the quirk that there’s been a small increase in Antarctic sea ice extent in winter, it raises interesting academic questions about the factors influencing sea ice melt rates. However, the fact that the vast majority disappears every summer means that variations in southern sea ice extent are truly insignificant and virtually irrelevant to any study of long-term of global ice mass loss. It’s a total distraction; a red herring; just a squirrel in the argument for those in denial.

  6. Kevin,

    It’s not just journalists on the Shokalskiy – scientists, too. More here:

    Yes, true. I should probably have been clearer there.

    I’m not sure what you mean by the comment on hemispheres, albedo, and seasons? Southern Hemisphere sea ice is increasing across all seasons, including the austral summer (southern hemisphere sea ice minimum)

    Yes, that’s a good point. That was probably poorly worded (as does happen here, given that it’s a blog and not a peer-reviewed paper). I was thinking, when I wrote that, more of the long-term trend than any short term variations. It may be true that for the last year or so there’s been an increase in the Antarctic summer that may (in an albedo sense) have cancelled any decrease in the Arctic summer (in an albedo sense), but in a long-term sense the trend in the Arctic is quite a bit faster than in the Antarctic. I guess there are many possibilities for the future, but one shouldn’t assume – I would guess – that some short term variations have any real significance with respect to long-term trends.

    I should also add that this was motivated slightly by people referring to the winter Antarctic sea ice extent being the highest in recorded history, (or something like that), but you’re right that an increase in summer extent would have an impact on albedo.

    The trends are interesting from the point of view of understanding climate processes at high latitudes in the southern hemisphere.

    Indeed, I was trying to illustrate that there are some explanations for the increase in Antarctic sea ice that may be related to a reduction in the ice sheet mass, but that this is not yet fully understood.

  7. Kevin says:

    Hi Anders,

    I don’t expect a peer reviewed article 🙂 I was just trying to understand what you were implying. Maybe the confusion here is the vagueness of ‘summer’ and ‘winter’. In any case, southern hemisphere sea ice extent trends are positive — but noisy — in the high sun, annual minimum, austral summer season (February-ish, about +4% \pm 4% per decade), but are indeed as you say much smaller magnitude than the negative Northern Hemisphere high sun, annual minimum, boreal summer season trends (September-ish, about -14% \pm 3% per decade). Source: http://nsidc.org/data/seaice_index/more-about-monthly.html

    There was an interesting paper this past summer from Polvani and Smith in GRL, http://onlinelibrary.wiley.com/doi/10.1002/grl.50578/abstract

    ‘The recent observed positive trends in total Antarctic sea ice extent are at odds with the expectation of melting sea ice in a warming world. More problematic yet, climate models indicate that sea ice should decrease around Antarctica in response to both increasing greenhouse gases and stratospheric ozone depletion […] we show that the observed Antarctic sea ice trend falls well within the distribution of trends arising naturally in the system, and that the forced response in the models is small compared to the natural variability.’

    cheers,
    Kevin

  8. Kevin,

    In fact, having thought more about why I wrote that; it was actually mainly because a few months ago various people were tweeting about how the Antarctic sea ice in winter was the highest on record. That should have no real influence on albedo. You’re quite correct, though, that an increase in summer would have an effect and I probably should have expanded on that a little. It’s tricky to get the balance right between saying too much and saying too little 🙂

    Thanks for the link to the paper. That would seem to be reaching a similar conclusion to that being suggested in the Swart & Fyfe paper that I linked to in the post.

  9. Manabe et al. 1991 page 811: “… sea surface temperature hardly changes and sea ice slightly increases near the Antarctic Continent in response to the increase of atmospheric carbon dioxide.”

    Oddly, most models after Manabe 1991 got SH sea ice wrong. Dunno why. Do they not model winds correctly? Do they not model the slowdown in mixing between Antarctic frigid surface waters and deeper warmer waters when extra fresh water (which also freezes easier) is dumped on the ocean via more moisture in atmosphere and rapid land ice mass loss?

    Maybe it’s time to go back to the future and learn what a 1990 era model (which likely ran on a “supercomputer” roughly as powerful as a smartphone) can teach us about SH sea ice…

  10. Tom Curtis says:

    There is an irony about the various sailors, scientist, reporters and tourists currently being trapped in sea ice. They are not trapped because of the growth of Antarctic Sea Ice. Although the current Antarctic SI is 1.5 million square kilometers greater than 1979-2008 mean for this time of year, it is nonetheless melting rapidly, including just north of Commonwealth Bay where the Shokalskey is trapped. Rather, it is trapped as a consequence of portions of ice shelves breaking of the Antarctic coast line. Specifically, in 2010, Iceberg B-9B, a remnant of a calving event on the Ross Ice Shelf in 1987, collided with the tongue of the Metz Glacier, breaking it of. The debris from that collision, it appears, has remained more or less in situe for the last three years, until strong winds shifted out from the terminus of the Metz Glacier towards Commonwealth Bay, trapping the Shokalskey. This is described in more detail on the mission blog.

  11. Tom,
    Fascinating, I did not realise that. Ironic, indeed, but not in the way many think. Maybe I should do more reading before writing my posts, but I seem to be able to rely on my regular commenters correcting any of my regular mis-understandings 🙂 Have a good New Year.

  12. Skeptikal says:

    Laugh, and the whole world laughs with you…. get stuck in ice, and the whole world laughs AT you!

    They went there to report on the melting ice… now they’re probably wishing it would melt.

    Irony… you betcha!

  13. Skeptical, did you read Tom’s comment?

  14. Skeptikal says:

    Yes I did… and, quite frankly, it doesn’t matter where that ice came from. The point is that the ice is there (in the Antarctic summer) and the ship is stuck. Had that ship been some hapless fishing boat, it would have barely rated a mention by the media or any blog site but being a cruise ship on a ‘scientific’ expedition to find evidence of global warming, it’s front page news.

    There’s a BBC film crew and some journalists from the Guardian on board… supposedly to report on how bad the ice melting is down there… I don’t think anyone can take a report of melting ice seriously when it’s coming from a ship trapped in ice.

  15. The point is that the ice is there (in the Antarctic summer) and the ship is stuck.

    Not really, but it’s New Year’s day and I really can’t be bothered trying to explain that ice in the Antarctic in summer is not the unexpected.

  16. jsam says:

    One way sceptics note Antarctic sea ice increase – but don’t want to talk about Antarctic land ice decrease, Greenland ice decrease, glacial ice decrease or the Arctic. There’s no-one less sceptical than a “climate Skeptikal”.

  17. Tom Curtis says:

    non – Skeptical clearly doesn’t care much about the facts of the case. In fact the expedition went south to:

    “1) gain new insights into the circulation of the Southern Ocean and its impact on the global carbon cycle
    2) explore changes in ocean circulation caused by the growth of extensive fast ice and its impact on life in Commonwealth Bay
    3) use the subantarctic islands as thermometers of climatic change by using trees, peats and lakes to explore the past
    4) investigate the impact of changing climate on the ecology of the subantarctic islands
    5) discover the environmental influence on seabird populations across the Southern Ocean and in Commonwealth Bay
    6) understand changes in seal populations and their feeding patterns in the Southern Ocean and Commonwealth Bay
    7) produce the first underwater surveys of life in the subantarctic islands and Commonwealth Bay
    8) determine the extent to which human activity and pollution has directly impacted on this remote region of Antarctica
    9) provide baseline data to improve the next generation of atmospheric, oceanic and ice sheet models to improve predictions for the future”

    (My emphasis)

    The reason the ship got stuck, again, is that:

    ” In 2010, a large iceberg known as B09B, calved from the continent and collided spectacularly with the extended tongue of the Mertz Glacier. The knock-on effect has been that Commonwealth Bay has filled with sea ice (termed ‘fast ice’), preventing direct access from the sea to Mawson’s main hut at Cape Denison. Unfortunately for the AAE, it appears the region has just undergone a massive reconfiguration of sea ice, years after the loss of the Mertz Glacier tongue.”

    (Again, my emphasis)

    So, having gone to investigate the impacts of “the growth of extensive fast ice” they got caught by some fast ice when it was shifted by strong winds. Doesn’t have quite the same ring as “They went there to report on the melting ice… now they’re probably wishing it would melt”? No wonder Skeptical prefers his manufactured version to what has actually occurred.

  18. Tom Curtis says:

    I might add that when non-Skeptical writes “…it doesn’t matter where that ice came from…” he gives the game away. If you are interested in reporting an event, ie, providing enough information so that people can genuinely understand it, clearly it makes a world of difference whether a large body of ice known to be in the vicinity for the last three years is blown into the ships course, trapping it; or a sudden freeze caused an unexpected ice build up when the ice was expected to be melting, thereby trapping the ship. If, on the other hand, your only interest is propaganda, the only difference the actual facts make is they must be kept suitably obscure as to not provoke thought in those you intend to delude. By his comment, non-Skeptical shows it is propaganda he seeks, not knowledge.

  19. angech says:

    Oh, yes- Climate scientist ship on expedition to show warming antarctic now deliciously, ironically, futilely and fatuously stuck in summer ice build up to record levels [for that time of year] in the antarctic.

  20. Victor Venema says:

    It is a pity so many people have nothing better to do on New Years Day as spreading the nonsense of WUWT and Co.

    Even if they would have been there to measure decreases in sea ice, which Tom Curtis convincingly argues they were not, a decrease in sea ice does not mean that the sea ice is immediately gone. Quite a logical error, no clear thinking human would make. Sounds a lot like political spin.

    To measure sea ice, you have to go near it. Why are the libertarians this time not praising the entrepreneurial spirit and risk taking as a major force that brings the world progress?

  21. johnrussell40 says:

    Angech/Skeptikal… While ever there is an ice sheet on the Antarctic land mass which flows down to the sea, there’ll be ice in the sea surrounding the continent; at all times of year. The measure of sea ice extent is defined as the area of ocean with at least 15% ice cover: yes, that’s just 15%. So an ocean that’s ‘ice covered’ (considered 100% ice) might still have up to 85% open water. Conversely an ocean that is called ‘ice free’ could have up to 15% ice present. And when the wind blows strongly towards the coast, that ice could be piled up, trapping any ship that’s was amongst the ice. Read up about ice extent here: http://nsidc.org/arcticseaicenews/faq/#area_extent

    Last, just because you want to prove that the polar icecaps are not warming, it doesn’t mean that the targets of your unpleasant remarks want to prove there is warming. Implying that indicates you have no understanding of how science works. Science just tries to find out what’s happening, which requires data gathering; including expeditions to inhospitable places where there is danger. So you should be pleased scientists are there: after all it’s their work that’s shown that winter Antarctic sea ice extent has increased. If scientists were as conspiratorial as the WUWT puppet masters seem to think, wouldn’t you have expected them to hide that fact?

  22. johnrussell40 says:

    Sorry, Victor. It looks like I duplicated some of what you said (this has happened a couple of times now). In fact I’m doing other things at the same time, so I start a comment and then become distracted. Then when I return, finish and post my comment I find someone’s got in before me!

    On the topic in question. I found this simple description of why winter sea ice extent is increasing, very compelling; “When winds push on sea ice, they tend to move it in the direction they are blowing, but the Coriolis effect adds an apparent push to the left. In the unconfined system of Antarctic sea ice, this pushes the ice northward away from the continent. By spreading sea ice westward and a little northward (and since we measure extent with a 15% cut-off) the gradual trend towards faster mean winds means a gradual trend toward spreading of the ice cover. It can be found here: http://nsidc.org/arcticseaicenews/faq/#wintertimeantarctic

  23. OPatrick says:

    It’s always good to be reminded of the paucity of ‘sceptic’ arguments, that they need to rely on paper-thin ‘ironies’ such as this to score cheap points. I hope that someone in the mainstream media will point out the real ironies in the false ironies that are being sold to the gullible.

    Kevin says above:

    Southern Hemisphere sea ice is increasing across all seasons, including the austral summer (southern hemisphere sea ice minimum), e.g. http://nsidc.org/arcticseaicenews/files/2013/12/Figure4b.png

    But the link doesn’t seem to support what he says, with 2012 showing ice levels returning to average by December and 2013 data stopping in November. It may well be the case that Antarctic sea-ice levels are above average in summer as well as in the winter, but is there a data set that actually shows this?

    JohnRussell says above:

    However, the fact that the vast majority [of Antarctic sea-ice] disappears every summer means that variations in southern sea ice extent are truly insignificant and virtually irrelevant to any study of long-term of global ice mass loss.

    However this seems outdated to me given that the almost equally vast majority of Arctic sea-ice also nows disappears each summer – I think the Antarctic melt is something like 80% whilst last year the Arctic melt was about 75%.

  24. OPatrick says:

    It may well be the case that Antarctic sea-ice levels are above average in summer as well as in the winter, but is there a data set that actually shows this?Looking here I think it appears that, percentage-wise at least the trend in summer extent is actually greater than winter extent.

  25. johnrussell40 says:

    OPatrick. I wouldn’t disagree. I’ve been reading up quite a bit on Antarctic ice in the last 24 hours and realise that I was probably a little out of date when I wrote that earlier comment.

    The true irony is that there’s been a lot of new work on Antarctic ice done in the last year or so, some of it by scientists making expeditions into the ice pack—which can be quite a dangerous activity.

  26. william says:

    a perfect start to the year, helping each other.

    “WUWT and WeatherBell help KUSI-TV with a weather forecasting request from ice-trapped ship in Antarctica Akademik Shokalskiy”

  27. Joshua says:

    So with more than 700 comments and counting at WUWT, over a topic apparently considered worthy of a “sticky-post,” and with much atwitter at other blogs in the “skept-o-sphere,” we have climate change “skeptics” quite focused on the implications of a short-term weather phenomenon as if that were meaningful for understanding long-term climate change.

    I would call that ironic – except that irony implies events occurring in a way that would be considered unexpected. The opposite is true here. This is “skeptics” acting in a way that is entirely expected. That’s how they earn their quotation marks.

  28. william says:

    maybe they should be building more of these for the Antarctic.

    “Russia has started building the world’s largest universal nuclear-powered icebreaker
    The Arctic will be granted the highest ice class – 9, meaning the ship will be able to break ice in the Arctic area all year round”

    Back in 2011 Hilary Clinton asked the Swedish government for a loan of ice breakers for the Antarctic , the Swedes said no, we need them.

  29. johnrussell40 says:

    I don’t think they’ll be building anything for the Antarctic, William. There’s no accessible oil been found there.

  30. Victor Venema says:

    William, you may be interested in reading this: Anthony Watts, most blessed and ethical professional hero @wattsupwiththat, rides gallantly to the Antarctic rescue.

    I really wonder, how it is possible that people assume that ships go to the Antarctic without having direct contact with a weather service. Even a merchant ship on a busy route will not do something that stupid and will have a contract with a weather information provider. Weather can be dangerous, having good information is of high economic value. (Meteorological departments are much, much larger as climatology departments.)

  31. Tom Curtis says:

    O.Patrick, Jan 1st 12:42 PM, cyrosphere today shows a graph of the SH sea ice area anomaly. As you can see, the anomaly has been positive through all of 2013, and is currently 1.5 million square kilometers. The total SH sea ice area is currently 6.88 million square kilometers. That is just under half of Antarctica’s 14 million square kilometers, indicating that sea ice increases by approximately a half the albedo of effect of Antarctica in the austral summer, and the anomaly increases it by approximately 8% (ie the percentage increase in area over that of Antarctica plus average SH sea ice area). The back of the envelope calculation based on area understates the effect by ignoring angle of incidence, but overstates it in that the baseline of the anomaly is 1979-2008 is greatly reduced from SH sea ice area early in the twentieth century. Because of the later, the sea ice feedback from global warming is currently positive in the SH, slightly less positive than it used to be.

  32. Kevin says:

    Tom,

    I think one needs to be extremely cautious if looking at pre-1973 sea ice data from the Southern Hemisphere in HadISST. As Rayner et al. (2003), say (their section 2.1.3):

    ‘Before the advent of satellite-based imagery in 1973, sea ice concentration data for the Antarctic are not available, and sea ice extent data are not readily available for individual months, seasons or years … Therefore our sea ice concentration analysis before 1973 is derived indirectly, and does not include any interannual variability, though there are some trends resulting from the differences between climatologies for different period.’

    cheers,
    Kevin

  33. OPatrick says:

    Tom, what is defnitiely clear is that what is happening in the Antarctic is far from clear! I’d be interested to know if there has been any further work on the pre-satellite Antarctic extent data tamino highlights, the pattern of which seems, at first glance at least, improbable compared to the satellite data.

    My earlier, failed, link should have been this one to nsidc concentration and extent graphs. It’s interesting that the summer months, December, January and February, have the largest increasing trends, in percentage terms, but are also the only ones which are not statistically significant.

  34. OPatrick says:

    Kevin, whilst I agree with you about needing to be careful the available data does certainly strongly suggest that prior to the satellite era the Antarctic sea-ice extent was significantly higher than it is now.

  35. Tom Curtis says:

    Kevin, from William de la Mare (1997),”Abrupt mid-twentieth-century decline in Antarctic sea-ice extent from whaling records”:

    “A decline in Antarctic sea-ice extent is a commonly predicted effect of a warming climate. Direct global estimates of the Antarctic sea-ice cover from satellite observations, only possible since the 1970s1–4, have shown no clear trends. Comparisons between satellite observations and ice-edge charts obtained from early ship records suggest that sea-ice extent in the 1970s was less than during the 1930s, an indication supported by limited regional observations. But these observations have been regarded as inconclusive, owing to the limited spatial and temporal scope of the early records. A significant data source has, however, been overlooked. The southern limit of whaling was constrained by sea ice, and since 1931 whaling records have been collected for every whale caught, giving a circumpolar coverage from spring to autumn until 1987. Here, an analysis of these catch records indicates that, averaged over October to April, the Antarctic summer sea-ice edge has moved southwards by 2.88 of latitude between the mid 1950s and early 1970s. This suggests a decline in the area covered by sea ice of some 25%. This abrupt change poses a challenge to model simulations of recent climate change, and could imply changes in Antarctic deep-water formation and in biological productivity, both important processes affecting atmospheric CO2 concentrations.”

    The first paragraph of the article reveals the basis of the analysis:

    “Whaling in theAntarctic began in 1904 from land stations and in 1905 the first floating factories were introduced. The early factory ships lacked slipways for hauling whales on board, but they could process the catch by mooring to an ice floe, leading to the fortuitous discovery that whales, especially the highly prized blue whales, tended to concentrate near the ice edge. The sea-ice margin is an area of enhanced biological productivity, and pelagic whaling concentrated near the ice edge for most of the commercial era. The introduction of floating factories with stern slipways led to the expansion of whaling around Antarctica, and by 1931 the pattern of whaling near the ice edge was well established.The whaling season usually began in October and continued through the Antarctic summer until April. The whaling fleets spread along the ice edge at the start of the season, following it southwards as it retreated. No pelagic whaling occurred from 1940 to 1946, but after the Second World War catching again concentrated near the ice edge. From 1957 to 1975, the scarcity of blue, fin and humpback whales led to whaling concentrating on sei whales in the region of the South Polar Front, well north of the ice edge. In 1972 whaling turned to the remaining abundant species, the relatively small minke whale. As with blue, fin and humpback whaling, minke whaling occurred near the ice edge, and became widespread until the end of commercial whaling after 1986/87.”

    The accuracy of the method was tested against two observational records from the era, with good fit. Thus we have significant evidence of a substantial (25%) reduction in sea ice extent over the 20th century in Antarctica.

  36. Tom Curtis says:

    OPatrick, I don’t know whether the pattern is improbable or not. I have good reason to think it is real, not just from HadISST as cited by Tamino, and de la Mare (1997), but also from anecdotal evidence relating to early Antarctic explorers who also became trapped in sea ice near Antarctica. What is clear is the mechanisms involved. It is plausibly suggested that the current growth in Antarctic sea ice extent is due to stronger winds breaking up the ice, allowing the open water thus created to freeze over; and to increased freshening of the sea water from mass loss from the Antarctic land ice and increased rainfall due to warmer weather raising the freezing point of sea water in the vicinity of the Antarctic. It is possible that these mechanisms would be much weaker the further north you go in that stronger winter sunshine would prevent the refreezing of open water from increased wind strength. That is, however, speculation. So, the pattern exists, but as de la Mare writes, it is a challenge to model the changes.

  37. BBD says:

    Further to what Tom says about strengthening zonal wind speeds, a few links that may be of interest.

    First, the emergence of the wind-driven upwelling hypothesis for enhanced basal melt of Antarctic ice shelves is described here, then see Pritchard et al. (2012) and Rignot et al. (2013).

  38. Kevin says:

    Hi Tom, (and OPatrick),

    My point was specifically about Southern Hemisphere sea ice concentrations in HADISST before 1973/79 (Rayner et al. don’t appear to use de la Mare’s 1997 whale proxy data, although they cite it for independent support). On the de la Mare 1997 paper, see Vaughan 2000 and also Ackley et al. 2003 in Polar Research (about potential biases in the method). There is a newer (2009) de la Mare paper in Climatic Change that I don’t have access to, but which from the abstract claims there is no bias. So, this seems like an open question. There is a chapter in the Thomas and Dieckmann (ed) book, ‘Sea Ice’ (from, I think, 2010) that discusses some of these issues as well.

    One of the challenges seems to be the spatial variability I mentioned upthread. With respect to pre-satellite sea ice extent, Nerilie Abram et al. had a paper a few years ago (2010, GRL) estimating past sea ice extent in the Bellingshausen Sea. They show a long-term 20th century decline inferred from methanesulphonic acid in ice cores, but at that location even the post-1979 satellite data also show a decline. So, regional differences are probably important pre- as well as post-satellite era. Overall there are numerous data points suggestive of more extensive sea ice prior to the 1970s, but I’d be cautious of some of the reconstructed large magnitude changes in the mid 20th century from, e.g. the whaling proxies and HADISST.

    Again, specifically regarding HADISST sea ice, which is the subject of the post you linked to:

    UCAR’s data guide on HADISST:
    https://climatedataguide.ucar.edu/climate-data/sea-ice-concentration-data-hadisst

    KEY LIMITATIONS:
    The effect of the many data sources on the continuity of the timeseries is difficult to track and assess. Many obvious non-climatic breaks in the record exist, especially in the Southern Hemisphere
    Shares weaknesses with source data, e.g. NASA Team, Chapman and Walsh NH sea ice, sparse SH pre-satellite observations
    Higher resolution and more homogenous (single algorithm) data are available for the modern satellite period, 1979-present.

    cheers,
    Kevin

  39. BBD says:

    To be clear, I haven’t read either of these studies and obviously cannot comment on them, but there’s more information in the press releases for Prichard et al. and Rignot et al. for anyone interested.

    If Kevin or Tom can provide more insight into either study that would be most welcome.

  40. Tom Curtis says:

    BBD, Prichard et al and Rignot et al discuss the effect of basal ice melt on the thinning of ice shelves. That is a distinct issue to sea ice extent, so not directly related to this particular discussion. It is tangentially related to the original post in that the ice currently trapping the ship came from the partial break up of one ice shelf in 1987, and the complete break up of another in 2010.

  41. Tom Curtis says:

    Kevin, I am unfortunately only able to find the abstract of Vaughn (2000), and de la Mare (2009) and so cannot comment on their contents.

    Ackley et al (2003) is interesting. They cite evidence that ship board observations tend to place the ice edge north of satellite observations; and reason to think this bias also applies to the whaling data. That is interesting, an certainly a relevant factor in trying to make a direct comparison between whaling data and modern satellite derived values. However, the reduction in sea ice extent shown by de la Mare is based on a comparison between earlier and later whaling data, not a comparison between whaling data and satellite data. Therefore this bias is irrelevant to de la Mare’s finding.

    Ackley et al also point out a potentially important bias in the behaviour of Blue Whales (the source of the data in the fifties) and Minke Whales (the source of the post 1970 data). They write:

    These problems were further compounded by the change in whale species hunted and principal regions in which they were hunted between the two periods (Fig. 5). The minke whales (Balaenoptera bonaerensis) caught in the later period are an ice-associated species found throughout the year in the ice zone, while the earlier blue (B. musculus) and fin whale (B. physalus) species migrate to ice edge from outside the pack ice zone.

    However, in de la Mare (1997) already addresses this issue, pointing out that the southern limit on whale catching was set by technological limitations, and that factory ships took station “…5-20 nautical miles north of the ‘hard’ ice edge” in both eras. Therefore this difference in biology is unlikely to significantly bias the results.

    More importantly, we are not solely reliant on de la Mare. De la Mare, HadISST, icecore proxy data, and even penguin biology (mentioned in the previous link) all point in the direction of a substantial reduction in Antarctic sea ice extent from c1950 to c1970. I’m a great believer in the consiliance of inductions. Therefore absent significant evidence to the contrary, I think we can accept that Antarctic sea ice extent reduced by about 20% (de la Mare’s 2009 figure) from the 1950s to the 1970s.

  42. BBD says:

    Tom Curtis

    Consilience is what I am wondering about really: are the increased zonal windspeeds and consequent upwelling and increasing extent of Antarctic sea ice all related? But perhaps this is going too far.

  43. Kevin says:

    Hi Tom,

    Ackley et al. 2003 say the following:

    ‘There is therefore no scope for a significant quantum transition in the circumpolar ice edge position in the 1960s as inferred by de la Mare from his analysis of whaling catch data as a sea ice proxy. Most of the difference between the earlier and later periods is explainable by the differences between ship and satellite observations and those significant changes seen are only regional variations with physical cause.’ (emphasis mine)

    The ice core paper you link to (Curran, van Ommen 2003) is, like the Abram et al. 2010 paper I linked to, reconstructing (maximum) extent from methanesulphonic acid in ice cores for a region where sea ice has actually been declining in the post-satellite era. Moreover, their inferred decline of ~20% is over the period ~1950 to the mid 1990s, not between 1940 and 1960 as de la Mare suggests.

    Given (1) potential unresolved biases in the whale proxy and (2) the lack of direct pre-satellite data (see caveats in Rayner as well as from UCAR), I remain skeptical of the magnitude of decline you seem to prefer. I don’t personally find that the evidence convincingly converges in the way you apparently find it does. I’d say the balance of the evidence does support greater extent in the early/middle 20th century vs. some/much of the satellite era, but I don’t think it is strong enough to support the large % change that you prefer.

    I am intrigued by the paleo/historical aspects of this, so I’ll be sure to ask Southern Hemisphere cryosphere folks about the current thinking on this as we cross paths over the next few months of travel. In the meantime, I’ll let you have the last word.

    cheers,
    Kevin

    Of possible interest, however only a WCRP conference poster and not a peer-reviewed article (see in particular their right side, middle of the page figure, and their conclusion ‘Antarctic sea ice fields in the HadISST data set are likely to be in error prior to the satellite era’):
    http://www.uca.edu.ar/uca/common/grupo72/files/Renwick_SAM-ice_poster.pdf

  44. Rachel says:

    The team have made it safely off the Akademik Shokalskiy:

    and some photos:

  45. Rachel says:

    And Richard Tol’s response to the rescue:

  46. Skeptikal says:

    Rachel, I agree with Richard Tol.

    Thanks for posting his response.

  47. johnrussell40 says:

    Yes, when the world is faced with a threat to its future, it makes much more sense to sit on your arse and throw spanners into the works of those trying to increase understanding of the problem.

  48. Rob Painting says:

    John, Tol is an economist – a glorified reader of tea leaves and goat entrails. I wouldn’t expect much sense from him.

  49. Rachel says:

    The idea that science can be conducted without taking observations (and taking some risks as in the case of trips to Antarctica) and measurements and performing experiments and calculations is known not as science but as the feelies. All that is required for the feelies is an armchair. It doesn’t cost a thing (other than purchase of said armchair) and doesn’t involve taking any risks.

  50. johnrussell40 says:

    Yes, I was aware and I feel about economists much as you do, Rob. In the past I found that I’ve been well ahead of them when it came to such things as predicting the housing boom and subsequent financial crash. The fact that they invariably disagree with one another and each develops their own pet theories suggests that it’s a discipline only one step removed from soothsaying.

    Having said that, I wonder if it’s embarrassing for people like Tol, who consider themselves to be legitimate academics, having people like Skeptikal and others frequenting WUWT, cheering them on?

  51. Victor Venema says:

    Rachel, you are right. And at other moments the unreasonables complain that scientists never get out of their offices. There is nothing that can stop their complaints and their alamism about solving climate change.

  52. Rachel says:

    Victor, yes, it’s quite extraordinary that people should now complain about scientists studying things like (from Tom’s comment above) the circulation of the Southern Ocean, changes in ocean circulation, the impact of a changing climate on animals living in the Antarctic and so on. Don’t we want to research these things? I think the unreasonables will complain no matter what.

  53. andrew adams says:

    Having read the comments at Judith Curry’s blog it’s actually pretty obvious that there is no need for researchers to make these kinds of expeditions as plenty of people manage to be experts on Antarctica without actually getting up from behing their f***ing keyboards.

  54. BBD says:

    andrew adams

    I stopped reading Curry for a reason, you know.

    😉

  55. BBD says:

    And I endorse what Rob Painting said about economists.

  56. BBD says:

    Incidentally, the relationship between increasing wind speed and increased Antarctic sea ice is discussed at Stoat. The relationship between increasing wind speed and upwelling is examined in the studies I linked above.

  57. Tom Curtis says:

    We should be careful to distinguish between macro- and micro-economics. Micro-economics is a careful discipline whose principles are tested against reality on a regular basis. It is probably the most scientific of the social sciences. That may sound like I am damning with faint praise – but I am not.

    Macro-economics is, far too frequently, merely ideology disguised with mathematics. For many macro-economists, there theories are not only poorly tested against reality, but not even consistent – or worse, retain a limited consistency only by ignoring obvious implications of their theories. There are some good macro-economists out there, who try far better than most to be consistent IMO (but that probably just means I find their results more to my liking than others).

    As to Tol’s contemptible comment, if their is any question about the organization of the trip, it is why did Turney attempt to defray the cost of the research to the tax payer by taking along tourists to a situation he knew to be potentially dangerous? I presume, of course, they were warned of potential dangers.

  58. AnOilMan says:

    Folks: I’d rather see a trip north in summer. Maybe those guys could go kayaking at Lake North Pole. It would make for some good pictures. Perhaps Dyson’s son could go for that?

    andrew adams: I stopped reading Judith Curry for 2 reasons.

    One: She [Rachel says: I have removed a couple of words here because I don’t like accusations of lies. It’s better to demonstrate a lie and then let other people judge for themselves.] has been aggressive about promoting bad data that any technical person can see through. (Would you like clear citations?)

    Two: I received pro-fracking advertising from the GWPF which strikes me as being completely at odds with all statements the GWPF makes about climate science. I mean, who says, drill more oil on one hand, and climate science must be wrong on the other? (Hint: Oil companies. Since I’m in oil, that is probably why I got the brochures.)

  59. BBD says:

    OilMan

    If you receive anything else from the GWPF, do please forward to johnrussell40. Don’t just bin it.

  60. > I think the unreasonables will complain no matter what.

    It might not be fair to say that they are complaining:

  61. > Would you like clear citations?

    Yes, pretty please with some sugar on it.

  62. AnOilMan says:

    BBD: No longer have it. It was publicly available way back when.. then the Natural gas bust hit (we stopped drilling 3-4 years ago), so no one in oil and gas cares. We’ll be interested when natural gas hits $4. 🙂

    willard: Old hat for you I’m sure;
    http://judithcurry.com/2011/10/30/mail-on-best/
    http://tamino.wordpress.com/2011/10/30/judith-curry-opens-mouth-inserts-foot/
    http://www.thegwpf.org/best-confirms-global-temperature-standstill/
    http://www.skepticalscience.com/baked-curry-the-best-way-to-hide-the-incline.html

    So… Note: Even i using a short term graph she relies on using strictly 40 data points for one month, which just happen to come from the arctic. That anchors down her short term graph, and of course being what she is, she’s also ignored the uncertainty in her own data set.

    [Rachel says: Sorry, OilMan. I’ve removed the last part of your comment because I’d prefer we didn’t accuse people of being trolls. Nice to see you back on the blog :-)]

  63. andrew adams says:

    I admit that complaining about stupidity at Curry’s blog is a bit like complaining about the British weather.
    Still, I think her activities are worthty of scrutiny given the position she holds and that she is treated as an authority on climate change in some quarters. And in some cases harsh words are quite justified.

  64. Rachel says:

    Still, I think her activities are worthty of scrutiny given the position she holds and that she is treated as an authority on climate change in some quarters.

    I agree with this. My only caveat is that we critique what she says rather than her personally. So no name-calling and no unsubstantiated defamatory remarks.

  65. jsam says:

    Sometimes, Rachel, the distinction between the behaviour and the person is all too fine. 🙂
    http://dilbert.com/strips/comic/2014-01-03/

  66. johnrussell40 says:

    There’s a chap called ‘Dr Norman Page’ with some crack pot ideas, who I’ve engaged over at The Carbon Brief [ http://www.carbonbrief.org/5538.aspx ]. He says, “…at the WUWT threads most (not all) commentators are discussing the data and their own ideas not supposed authorities, also data based comments are not moderated out as they often are on the warmist sites”.

    Some of you might like to comment, but beware of the comment policy. I’ve said all I want to say to him.

  67. Rachel says:

    Sometimes, Rachel, the distinction between the behaviour and the person is all too fine.
    jsam, I’m not going to disagree with that! Funny cartoon too.

    JohnRussell,
    All I can say is wow! He thinks we should be preparing for global cooling.

  68. johnrussell40 says:

    There’s a new Guardian article written by Prof John Turner of the British Antarctic Survey about the ship and it’s titled “Antarctic sea ice increase is because of weather, not climate”. Now tell me I’m wrong but although the ship is trapped due to weather, isn’t the increase in Antarctic sea ice as much due to climate change as the loss in Arctic sea ice?

    Note I’m not saying Prof John Turner is wrong, I’m just questioning whether the sub editor who wrote that title is right. What do others think?

  69. Rachel says:

    It does seem a bit strange to me too, John. I see you’re asking about it on Twitter. Let us know if you get any reasonable responses. If the sea ice is partly debris from an iceberg calving a few years ago then it’s hard to see how climate change is also not a factor here.

  70. Tom Curtis says:

    johnrussell, the increase of antarctic sea ice around the ship was due to weather, ie, strong local winds blowing a mass of thick ice formed by the disintegration of a glacial tongue three years ago into the ships course. The increase in antarctic sea ice extent is probably due to climate. The two are different and largely unrelated factors.

  71. Tom Curtis says:

    Rachel, ice bergs have calved of Antarctic right through the Little Ice Age, and probably right through the last glacial. Therefore it is impossible to say that this individual calving would not have happened absent global warming. There is some evidence that the rate of calving has increased in which case the probability of the event may have increased due to global warming, but my understanding is that past rates of ice berg calving are insufficiently quantified such that the change in frequency of calving is not yet calculable.

  72. johnrussell40 says:

    I’ve just sent Prof Turner an email. It will be interesting to see what he says. The Guardian’s subs have written several dodgy headlines in the last month or two.

    Mark Brandon (@iceymark) seemed to tentatively agree: “I think jury is still out on reasons for increase in Antarctic sea ice. But I was pointing at the content. JT is v good. I think he might be waiting to see what others think (and perhaps he thinks that JT is responsible for headlines).

    Dana has just responded with “it’s debatable. He’s arguing it’s weather changes, but are those due to climate change? Complicated question.

    Well I don’t get it: if “it’s complicated” and “the jury is still out”, Guardian shouldn’t make a bold statement like “it’s not climate, it’s weather.

  73. johnrussell40 says:

    Tom, I know; that’s my point. The Guardian’s headline is “Antarctic sea ice increase is because of weather, not climate” ; and you’ve just confirmed it is wrong. http://www.theguardian.com/world/2014/jan/03/antarctica-ice-trapped-academik-shokalskiy-climate-change

    As it is, it plays right into the hands of those in denial: they’ll be posting links to that article from now to kingdom come if it’s not changed? You agree?

  74. johnrussell40 says:

    At last! John Turner has replied: pic.twitter.com/d6JOmV397W

  75. Rachel says:

  76. Rachel says:

    Therefore it is impossible to say that this individual calving would not have happened absent global warming.

    Ok thanks, Tom. On other matters, I hear it’s a bit hot in your part of the world at the moment?

  77. Tom Curtis says:

    john russel, sorry, missed your last line. And yes, the title is misleading, but that’s what sub-editors are for.

  78. johnrussell40 says:

    Thanks for posting that, Rachel. I’m working now to get the Guardian to change the article otherwise it’ll become the link to a denial meme. If anyone does Facebook please can they encourage John Turner to ask the Guardian to revise the headline.

  79. johnrussell40 says:

    Yep, Tom, I think they often choose subs for their ignorance and inattention to detail. 😉

  80. Tom Curtis says:

    Rachel, its not so bad, although it might be a tad warm later on.

    Fortunately, what I have heard, no tourists managed to kill themselves out west, although they gave it a good try.

  81. Tom Curtis says:

    john, don’t forget the bad puns. Can’t be a sub if you punning does not demonstrate a wit a cockroach would be ashamed of.

  82. While I am happy that the expedition members are safe and there appears to be no immediate danger to the crew still on the ship, the Guardian has suggested this ship may be fast in the ice for the next three years. In fact is, as of this morning there are now two ships held fast. Given that weather conditions are unpredictable there has to be a chance that these ships may be crushed by ice at some point and join other ships sunk in the Antarctic. If that happens there is a risk of a major environmental incident from diesel oils etc carried by these ships. Has this been considered and how would the threat be minimised?

  83. Rachel says:

    John,
    I see the Guardian has changed the headline for that article. That’s really great. I didn’t have high hopes.

    http://www.theguardian.com/world/2014/jan/03/antarctica-ice-trapped-academik-shokalskiy-climate-change

  84. johnrussell40 says:

    Sure thing, Rachel. If you check @icey_mark Brandon’s tweets, he said at 9:30 this morning: “headline has been revised john. It’s much clearer. Well done”. I tweeted several Guardian journalists and I believe it was Adam Vaughan, who’s head of the Environment section, who actioned it. I guess it’s just a case of getting to the right people. I think it was very important to make this change because, as I said before, those in denial would have been linking to it for evermore.

    What did surprise me was how reluctant the climate scientists were to say, outright, it was wrong. I guess it was loyalty to John Turner who they might have thought actually wrote the headline.

    It’s important to say things like they are. I am a Yorkshireman, born and bred, after all! 😉 Thanks for your help.

  85. Rachel says:

    It’s important to say things like they are. I am a Yorkshireman, born and bred, after all!

    I completely agree. This must be why I like Yorkshire so much. 🙂

  86. OPatrick says:

    Does anyone know of any up-to-date reconstructions of Antarctic sea surface temperatures? I’ve found it surprisingly difficult to find any. I’ve seen reference to this from Bob Tisdale, but obviously I am sceptical that it fully represents the state of knowledge given the source.

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