Iceberg Alley And Global Warming
    By Patrick Lockerby | June 6th 2010 09:21 AM | 24 comments | Print | E-mail | Track Comments
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    Retired engineer, 60+ years young. Computer builder and programmer. Linguist specialising in language acquisition and computational linguistics....

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    Iceberg Alley And Global Warming

    In 1912 there were 1,019 icebergs reported in the North Atlantic shipping lane throughout the iceberg season.  Many of those icebergs were reported in April 1912.

    This year, as of June 06 2010, no icebergs have been reported in that same shipping lane.

    Is this evidence of global warming?

    It is so intuitive to assume that, if  Arctic ice retreat is due to global warming, then a lack of Atlantic icebergs must also be due to global warming.

    It doesn't work that way: there is only an indirect link between sea ice loss and iceberg melt mechanisms.

    R.M.S. titanic

    The history of iceberg watching

    What is wrong with the following sentence?

    "In 1912 a ship was damaged by collision with an iceberg."

    I think that most people would find fault with the word 'damage'.  The Titanic wasn't just damaged, she was sunk.  But the real fault in the sentence is the use of the indefinite article 'a'.

    In 1912, RMS Titanic was not the only ship to hit an iceberg and suffer damage.  The following ships all suffered damage in the same shipping area following encounters with icebergs.

    Empress of Britain
    La Bretagne

    Credit to Thomas E. Golembiewski of for that information.

    Prior to the establishment of the International Ice Patrol in 1912 there was only an informal reporting of ice between ships.  Not all ships had radio.  Of those that did, not all kept 24 hour radio watch.  The Titanic's radio room was not a ship's service, but primarily a passenger facility for the sending of private messages by telegram.

    Recognising the need for oversight of the shipping industry, various governments got together to regulate safety at sea by international agreement.  Under that agreement, since 1912 the International Ice Patrol has monitored icebergs in the danger zone.  It is a tradition of the USCG International Ice Patrol to lay a wreath from a ship or aircraft on April 15 at the site of Titanic's loss.

    Titanic Memorial service 1994
    Photo credit:

    The history of an iceberg

    Year on year, snow falls on the Greenland ice cap.  Over the course of many thousands of years, many feet of snow are compressed into mere millimeters of ice.  Under huge pressures of the weight of ice a few kilometers thick, the ice flows from a high central mound to the ice edge.  Eventually, ice thousands of years old is calved into the sea around Greenland.

    Despite prevailing Northerly winds, the new iceberg doesn't head off South.  It may have to first make its way to the open sea via a fjord.  There may be islands in the fjord or its outlet.  At any time the iceberg may becomes stranded ashore or on a bar of rock debris.  In winter, the berg will be iced in and immobile.  It may take a year or more for our iceberg to emerge into open waters.

    Iceberg drift patterns in Baffin Bay.
    Image reduced in size and label added.
    Original map mcr4080.jpg - courtesy The Atlas of Canada

    Icebergs are much more affected by currents than winds.  Nine tenths of an iceberg is immersed in water, a much denser medium than air, so it is hardly surprising that iceberg drift should be dominated by currents.

    The historical prevailing current trend around Greenland has always been down the East coast, around the cape, up through Baffin Bay along Greenland's coast and then back South along the pack ice edge.  Up to and including 2007 there has always been substantial pack ice along the entire East coast of Greenland.  That pack ice would slow the progress of any iceberg calved along the East coast.

    One of the most prolific sources of icebergs is Sermeq Kujalleq, the Jakobshavn glacier, which produces about 10% of all icebergs originating in the Greenland ice sheet.

    Icebergs in Disko Bay. Terra 500m True Color image for 2010/156 (06/05/10)
    Image source:

    The small dots in the image above, at a resolution of 500m per pixel, are actually huge icebergs of the type seen in the next image.

    Icebergs in Disko Bay, Greenland. Photographed from Sarfaq Ittuk of Arctic Umiaq Line.
    12 July 2009

    Credit: Algkalv, Wikimedia commons.

    Our iceberg, from whichever part of Greenland's coast, will journey in the currents.  Every time it enters shallow waters it is at risk of stranding on a falling tide.  If neaped - stranded on an exceptionally high tide - it may remain stranded for a month or more.  The journey along Greenland's coasts is very slow.  Where the current loops back in Baffin Bay, our iceberg is carried towards the West.

    Our iceberg will now encounter any one of three conditions: little or no sea ice, loose pack or dense pack.  If there is no ice barrier our iceberg will be carried down the coast and subjected to more stranding risks.  If there is loose pack then the iceberg, being deeper than the pack, will feel the effects of current more than the pack.  It will be the bully in the crowd, trying to force a way through.  But this will serve to compact the loose ice ahead of the iceberg and thus slow its progress South.

    The greatest melt of an iceberg is due to erosion by waves and immersion.  By comparison, melting from direct solar heating or wind is much lower.  This means that every time an iceberg is stranded on a falling tide its area of water contact is reduced, hence its melt rate.  An iceberg surrounded by solid sea ice has its immersed area reduced by the area contacted by the surrounding pack.  The pack absorbs some of the heat from the water.  All in all, a stranded iceberg or an iceberg trapped in the pack is going to melt a lot slower than if it continued to follow the current freely.

    If the pack ice is fairly compacted, our iceberg will tend to remain in open water as it bounces along the edge of thick, compact ice.  In such conditions a large iceberg may easily survive melting long enough to end up in the Labrador current.

    In summary, for an iceberg to end up as a hazard to shipping in the North Atlantic great circle route, it must get to the Grand Banks area faster than its own specific melt rate.

    The next image is the most recent iceberg chart from the Canadian Ice Service.

    Iceberg analysis chart, reduced by me to 30% of original.

    Any iceberg which survices long enough to drift south of the limit shown in magenta will be picked up by the USCG International Ice Patrol.  As soon as ice conditions warrant it, the IIP issues daily bulletins.  As of the date of writing, June 06 2010 no such bulletins have been issued.


    Historical accounts, modern eyewitness evidence, scientific articles and scientific papers all point to the great length of time taken by any average iceberg to find its way down to the Grand Banks area - often many years.

    During the whole of its journey an iceberg is subjected to at least some melting from contact with warm currents or water warmed by the summer sun.

    There seem to be  two factors most likely to accelerate an iceberg's journey South:

    1) loose pack in Baffin Bay driven South as a body by wind and current;

    2) dense pack in Baffin Bay into which the berg cannot penetrate.

    A berg which cannot penetrate the Baffin Bay pack cannot get close enough inshore to be stranded.  Accordingly, it will continue to be driven South by the current.

    It seems that pack ice fragmentation and pack ice compaction cannot both be caused by global warming.

    There is no clear trend in Grand Banks iceberg counts.

    There is no clear link between Grand Banks iceberg counts and global warming.

    It seemingly follows that neither annual nor decadal variations in iceberg counts can be attributed to global warming.


    Many thanks for taking the time to share this fascinating story.

    Quite an interesting article, Patrick.

    I never new before that there had been that many ships that were damaged by collisions with icebergs. It seems that every time I read one of your articles I learn something new.

    Have you ever seen a photo of beached icebergs? That has got to be one of the weirdest sights that I have ever seen.

    Thanks for the great article. : )
    It seems that every time I read one of your articles I learn something new.

    Ditto!  :-)

    I discovered this information whilst researching news reports of weather in the Grand Banks area for 1912.  I was trying to discover if the ice conditions of 1912 were considered by contemporaneous reporters to be exceptional.  They weren't.

    I came across a newspaper report of a ship which struck ice and suffered damage, followed by the crew panicking.   There is a type of reporter who enjoys writing garbage comparing 'Johnny Foreigner' with 'our gallant British seamen'.  On searching for a more accurate version of the event, I came across  The rest, as they say, is history.  Literally. :-)

    Have you ever seen a photo of beached icebergs? That has got to be one of the weirdest sights that I have ever seen.
    I like the photos - exceedingly rare - that show a human or a small boat close to the berg for scale.  'Wow' doesn't quite cut it.

    I'm still trying to find 'the perfect photo' showing how some icebergs erode in exactly the same way as rock layers.  Ice layers tend to be of fairly uniform strength, but once in a while a berg will have layers of ice which are more subject to erosion than others.  Even more rarely we find bergs with eroded layers in different shades of blue.  The resulting shapes are visually stunning.
    Hi Patrick, thanks for yet another interesting read!

    If it's OK, I'd like to inform you that I have set up a little blog dedicated to news and data concerning the Arctic Sea Ice. I don't know how interesting it will be for me to do or for others to read, but we'll find out soon enough.

    The blog is HERE and I'll be sure to refer to your articles and updates, if you'll allow it.

    Neven:  I am very happy and grateful for any links to my articles in your blog.  It is good to know that my efforts are appreciated.

    I like what you have written so far and wish you well with your new blog.

    Maybe you could start a blog here at also.  That way, you are guaranteed at least one reader - me. :-)
    Patrick, I've written a new post today with multiple links to your Arctic Ice and Arctic Tipping Points series and your Broken Bridges of Nares article in particular. It boils down to the question whether it is at all possible that Greenland becomes circumnavigable (which BTW is a beautiful word) and whether this has happened before. I'll be mainly asking questions like that one on my blog, as I know very, very little about anything!

    Neven: that's an excellent article.

    I'm happy for you to use images and extracts from my articles the way you do.

    Images that I use without credit to the source are most commonly public domain, but some, very few, are my own work.  If in doubt, just ask.

    ... the question whether it is at all possible that Greenland becomes circumnavigable (which BTW is a beautiful word) and whether this has happened before.
    I raised that possibility in Arctic Tipping Points - #1: Background And Recent History.

    Greenland has been circumnavigated before, but by kayak and sled:  Lonnie Dupre and John Hoelscher, 1997-2001.  It has never, to the best of my knowledge, been circumnavigated entirely by any kind of boat or ship.  The reason is, you may guess, that there has never previously been navigable water between Nares Strait and Fram Strait.  That could change this year.

    The only source that claims a previously circumnavigable Greenland is 1421:The Year China Discovered America.  Serious researchers who have examined the claims made by Gavin_Menzies in that book suggest that he is either not understanding historical documents or else he is just making stuff up.

    I'm happy for you to use images and extracts from my articles the way you do.
    Images that I use without credit to the source are most commonly public domain, but some, very few, are my own work. If in doubt, just ask.

    Thanks, Patrick. If I do something of which you do not approve, then tell me and I'll remediate it immediately.

    Wrt circumnavigation: will it only be possible to circumnavigate Greenland in something large when the Arctic is completely ice-free? In other words, will the last ice be clinging to Greenland and Ellesmere Island? Or should it be possible as well when for instance say 2 million square km of sea ice extent is left and clings somewhere else?

    I'd read part of Arctic Tipping Points a while back so I'd forgotten about it. I'll copy the relevant part for an update of my post.

    Neven: if an icebreaker or other suitably strong ship made its way through loose pack around Greenland's shore ice, that would be a circumnavigation.  Following the actual coast - coasting - is not necessary to claim a circumnavigation.
    Patrick, for me it only counts if it's a sail boat like the ones who crossed the Passages in the last few years (forgot the names of the boats). Anyone can circumnavigate with an icebreaker! ;-)

    Anyone can circumnavigate with an icebreaker!

    Just so, but nobody seems to be planning to circumnavigate Greenland entirely just yet, even in an icebreaker.  The first entrepreneur to do that commercially will make oodles of boodle1.

    This would be the next best thing for anyone with the required amount of money and stamina.

    [1] - oodles - a great amount.  boodle - wealth, originally 'oodles of Boodle's (implied: jewellery) from Boodle's Jewellers, est. 1798.
    That's hilarious! Is it for real? If so and if you'll allow me, I'm writing a blog post about it tomorrow.

    If I win the lottery some time soon, we're going on that voyage, Patrick! Let this be a promise.

    It's as real as apple pie and Wikipedia.

    And you don't need my permission to blog on the same topics as me.
    Just don't write better articles than me, that's all.

    "Just don't write better articles than me, that's all."

    I wouldn't be too worried about that. :-)
    Besides, as soon as my wife finds out that I've started a blog, she will pull out the plug.

    Follow-up to above.

    I just remembered where I got the 1421 info - 'the' 1421 web site:
    The book’s claim that the winds and currents in these waters ensure that a “ship circumnavigating Greenland in this way would never have to sail into an opposing wind or current at any stage” (346) is utter fabrication.  At any time of year the winds in both the Davis Strait and Baffin Bay are as unpredictable and treacherous as the frequent fogs, and while experience with the local currents would certainly factor into a navigator’s plans here as elsewhere, one wonders what experience these apocryphal Chinese travelers might possibly have had at their disposal in planning to coast a huge land mass as completely unfamiliar to them as the sea next to it.
    Very interesting stuff, Patrick. If 2010 comes close to the record-breaking-zone and Greenland becomes circumnavigable, that one is sure to pop up on certain parts of the blogosphere. Better keep it handy and be the first to write about it in case 2010 goes on that melting spree. That would make it a debunking avant la lettre. ;-)

    Who would ever think something boring as melting ice could be so exciting!

    Hello Patrick,
    I love your articles. I absorbed every detail.

    I am a nature photographer who specializes in photographing icebergs off the coastline of Newfoundland, usually from my native small island of Twillingate.

    I photograph these bergs often times in their final days. I am in the process of completing a series called the "Death of an Iceberg".

    I have a question if you don't mind. Do you think we could possibly see the end of icebergs visiting the shores of Newfoundland in this century? Do you have an opinion as to how early this could possibly happen?

    For Eric: - The last day of an iceberg.

    Terry Adey

    Hello Terry, and thanks for your comments.

    Questions are always welcome.
    Do you think we could possibly see the end of icebergs visiting the
    shores of Newfoundland in this century? Do you have an opinion as to
    how early this could possibly happen?

    Those questions are very difficult to answer with precision and I know of no scientific study which attempts to make such predictions.  However, we are seeing many changes in the Arctic.  Most relevant to your question: there appear to be changes in circulation patterns.

    In a sea-ice free Baffin Bay the circulation could possibly slow down enough to allow strong Northerlies to carry bergs out of the Northward stream and eventually into the Southward stream.

    I am fairly confident that a generally sea-ice free Arctic, especially one with open water surrounding Greenland, will lead to a doubling of the rate of iceberg production from the Greenland ice sheet.

    The increase in berg production should at least partially offset faster berg melting, hence the number of bergs arriving at Grand Banks would not likely drop to zero.

    That is my best off-the-cuff educated guess, for now.  I intend to do some more investigation into the topic.


    I like your photos very much.  If you want to post any pictures or thumbnails here, please feel free to do so.

    I have an article on phytoplankton in progress.  May I have your permission to use your photo
    death_of_iceberg0005 as one of the illustrations?

    The phytoplankton is near the rock, lower left.  As to the bright green, I wonder if this berg originated in Kobbermine Bugt.
    Hi Patrick,

    Thank you for your responses. I appreciate all of them.
    Feel free to use the image. If you want it in a higher resolution just let me know.

    If any of my images can help you with your ice blogging feel free to ask to use them. It would be my pleasure to help. I respect the scientific community tremendously.

    Terry Adey

    Thanks, Terry.  That's very generous of you.
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