How soon will effects of increased Greenland ice cap melt be obvious

[philb]

to most in coast areas?

Scientist document Increased rate of melting of Greenland glaciers and ice cap, http://www.livescience.com/forcesofnature/041209_runaway_glacier.html http://news.independent.co.uk/environment/article328217.ece Dr. Gordon Hamilton, Univ. of Maine, http://www.greenpeace.org/usa/press/releases/greenland-glacier-nearly-tripl (Sermilik glacier in southern Greenland) Danish scientist Carl Boggild of GEUS, the Geological Survey of Denmark and Greenland
http://news.bbc.co.uk/1/hi/world/europe/3922579.stm

[Richard D]

1. the article I read . . .

. . . and I don't recall the source, said that at the old projections, total meltdown was projected for 1000 years. Now it's been reduced to 500 years.

[philb]

3. Are you suggesting that the 8 to 30 inches rise projected this century

won't be very significant (or catastrophic?)

and how much impact do you expect over the next 5 years?

on coastal erosion, salt water intrusion, loss of coastal property and estuary changes, more powerful hurricanes, etc.?

[Richard D]

5. Not at all . . .

. . . just trying to answer the question that was asked. Any sea level rise will change the way that the world is for the worse. I am of the opinion that we are in for some very deep shit, and that it's likely too late to put a stop to it. All we can hope for is a global waking up, especially in this country, and that people will do their best to ameliorate the situation.

Sorry if I gave the impression I was taking it lightly. Not the case at all.

[philb]

2. Minimum of 8 inches sea level rise expected this century

and expected level is much more

Sea level rise of at least 8 inches expected in this century
Gerald Meehl et al, National Center for Atmospheric Research (NCAR). Science March 18, 2005
Based on the NCAR model, global sea levels are expected to increase at least 4 inches in this century due to thermal temperature increase only. Add the probable melting in, and seas could rise 8 inches through 2100 in the best-case scenario, Meehl and his colleagues say. The rise is likely to swamp some coastal cities and villages, shrink islands, and make hurricanes and other extreme weather events more catastrophic.

http://www.livescience.com/environment/050317_global_warming.html
http://www.livescience.com/forcesofnature/041101_disaster_report.html

[Boomer]

6. I expect a nasty surprise

In the five years or more that I've been following global climate change reports, the one constant is the underestimation of the rate and degree of change. And every revision issued by scientists has been to paint a bleaker picture than they had imagined.

Lately I've read a few articles on the lack of complex modeling for glacier melt. As one researcher described it, the predictions of melt were based on a concept of one big block of ice subjected to heat and seeping at a constant rate. But a few researchers are learning that the mechanics are much more intricate, which suggests that once again we're being too optimistic with those "500 years" figures.

One of the scenarios described was of giant pools of melt water being held back by ice dams. When the dam breaks, enormous quantities of water are released. Another dynamic is the way in which melt water seeps under the glaciers to create a hydroplane effect that moves the glacial ice faster down an incline. There are also different densities of ice that react differently to climate conditions and that affect the integrity of the glaciers.

So while we can't predict exactly how these factors will take effect, I'm willing to go out on a limb and say the more we learn, the more worried we will become.

[1monster]

4. I've been telling my son since Kindergarten that he should plan to move

inland when he gets out of school (high school or college). I mentioned that to someone the other day and she thought that the coastline would not be changing that quickly... The Greenland news flash came after the conversation.

But, I remember pieces of coastline where there was about a thousand feet of beach at low tide and then a major two land thoroughfare running north and south beyond the dune line. That was thirty years ago when I moved to Florida.

Today, that north/south highway is out in the ocean. You can't even see pieces of it at low tide anymore. And the Atlantic gets closer and closer to the replacement highway every year.

[Dogmudgeon]

7. The Greenland melt won't happen in isolation

Due to where it is, it is conceivable -- even probable -- that accelerating freshwater ice melt from Greenland could stop thermohaline heat transfer in the northern North Atlantic (generally, everything above 45N). This would have a tremendous impact on the weather in North America and Europe alike, since it is the area in which the NAO, or the North Atlantic Oscillation occurs; the NAO is a major "teleconnector" associated with the northern Jet Stream.

The last major disruption of the thermohaline current in the North Atlantic happened about 10 kYA and resulted in the Younger-Dryas "cold snap", a mini Ice Age that lasted some 2000 years. The source of the fresh water was a huge lake of meltwater that had formed in the Laurentide ice sheet during the recession of the Ice Age.

Of course, there are many other processes, some global in scope, that we have to stay aware of, too. Overall Arctic heating and air inversion in the summer is a going to play an increasingly important role, as it has for the past four or five summers. And the thermohaline current in the northern Pacific is looking to be more important than we previously thought.

My own reading tells me that climate change events are "biphasic". In a Heinrich Event, which is a "cold" event, there is usually a spike of heating, perhaps as much as 20C, over a short period of maybe 10-50 years; the heat "collapses" quickly into a cold period characterized by worldwide winter weather patterns. So if human activity had primed the climate for a Heinrich event, we can expect to see extreme global warming, followed by a collapse in worldwide temperatures and climate displacement. In other words, no agricultural "breadbaskets" for several years.

I'm not sure how far the ocean level would drop in the aftermath of a Heinrich event, but the last major Ice Age (called the Würm in Europe and the Wisconsonian-Illinoisian in North America) tied so much water up in the ice caps that the ocean level dropped 200-300 feet. So, the water level is likely to rise for a while -- another inch, a foot, maybe a few feet -- and then fall back as the ice caps re-form.

Since we are in an overall Ice Age right now, our current warm period -- called an "interstadial" -- could end at any time, from human OR natural processes. Our continuation as a civilized species depends on our intelligent response to these major climate changes. We have not been doing a very good job in dealing with the smaller problems we've encountered, so the time left to us to learn is growing short.

--p!

[Odin2005]

8. I though Heinrich events...

only occured during, and just after (upper dryas event), glacials, and they don't cause as nearly as much warming as you say they did, they cause a warm-up to a temperature intemediate between full glacialand full interglacial. I've never heard of Heinrich events occuring in interglacials. The term "interstadial" is the short warm periods DURING a glacial, I think you are getting that term and interglacial mixed up. My understanding of the Upper Dryas (which lasted a few hundred years, not 2000, BTW) event was that it was caused by the partial draining of Lake Agassiz, sending all that fresh water into the north Atlantic, preventing the water near Iceland to sink, weakening the North Atlantic Drift. This is the reason I don't like these "Global Warming causes Upper Dryas repeat" hypothesis. Melting of glacial ice into the North Atlantc will weaken the sinkage near Iceland, but it is my understanding that only a rapid ourflow from a body of fresh water onto the Noth Atlantic will cause an Upper Dryas-like even, glacial melt from Greenland would not put enough fresh water fast enough to turn the Thermohaline circulation off completely.

Also, many climatologists think we are living in a Long Interglacial, an occurance that happens, IIRC, every 400,000 years. "normal" interglacials last about 10,000 years, while long interglacials last about 30,000. Long interglacials are caused when the tilt and precession parameters are right of a glacial to start, but it is delayed by one precession cycle because the earth's orbit is at it's most circular (like it is now). It needs to be slightly more eliptical for precession to have an effect on climate. So, no we are not at risk for our interglacil ending.

[Dogmudgeon]

9. Some clarification (Dial-Up Warning: long post)

First, anywhere you think I'm making an absolute statement ... I'm not. The fault for being unclear about that is mine. I assume that my readers understand my own tentativeness when it may not be readily apparent. However, I'm not trying to duck responsibility for my errors; I used to post disclaimers, but thought that was just a little too clever.

I also prefer to write informally, off-the-cuff, but your "challenges" got me thinking about a lot of these points, so I spent a few hours digging deeper into them. Just the time I put into the Milankovitch-ian work was a revelation, since the last reading I did on planetary element cycles in climatology, it was being "debunked" (and I hold "debunkery" in very low esteem).

Obviously, I am a frustrated academic of some sort, though climatology is not the field I was trained in. I was into neuro-bio-psycho-whatever and eventually did find work in the field about 5 years after graduating. But, alas, a B.A. got one into very few doors in the 1980s, and nowadays, it's useful for nothing more than being appointed Head Janitor, where "head" means "toilet". And unless you have an M.A., they make you pay for your own brush.

So here's what I found:

1. Heinrich Events and their occurrence: I've never seen any reference about whether they can or can not occur during interglacial periods. The six "canonical" Heinrich events (H1-H6) have all occurred during the most glacial period, though the Younger-Dryas, which is possibly an Heinrich Event (H0), happened during the present interglacial.

I've seen several papers extending the six (or seven) Heinrich Events into the 20s, mainly by extending the time frame under study back as far as 400 kY. Again, I haven't seen any conclusions about their connection to glacials. These Heinrich Events are probably subject to far more dispute, though.

2. Interstadial vs. Interglacial: Steven Earle's page at http://www.mala.bc.ca/~earles/mh-instability-apr00.htm has the following definitions:

Interglacial: A period of warmer temperatures and diminished ice sheets occurring between periods of glaciation. The last 10,000 to 15,000 years (the Holocene) is probably an interglacial, since its temperatures and the distribution of vegetation are similar to those of earlier interglacials.
Interstadial: A relatively brief interval of warming within a major glaciation. Durations of a few hundred to a few thousand years are common.

It appears that my own use has either been wrong all along, or has been superseded by better-defined use of the terms in the past decade. (Probably the former!)

Incidentally, Earle's article at that page, Instability of methane hydrates during interstadial periods, is relevant to many issues in climatology and energy development.

3. Duration of Younger-Dryas: This hasn't been settled by a long shot, and some climatologists even debate whether it was global. Using the GISP-2 ice core analysis, Paul A. Mayewski and colleagues have proposed a figure of 1300 ± 70 years, with a temperature rise of 7C at its end. (see The Younger Dryas from "U.S. National Report to International Union of Geodesy and Geophysics 1991-1994"; Reviews of Geophysics Vol. 33 Supplement 1995. ISSN 8755-1209). My figure of "about 2000 years" was a little long, though I've seen that number used, and it was probably the one that stuck in my head.

4. Lake Agassiz and Paleoflood dynamics: I believe you're more correct than I am on this point, though the idea I supported it with isn't fully dependent on it. For some reason -- perhaps pre-1990 reading and/or confusing it with reading about Heinrich Events (q.v. Wikipedia) -- I had connected this event to the Laurentian (approximately Quebec), not the Athabascan (approximately Alberta), area. The basic idea of fresh water spilling into the North Atlantic, though, is the main point. One of the first papers I found online, by Timothy Fisher, came to the conclusion that the paleoflood lasted about 78 days and discharged an average of 2.4 x 10^6 cubic meters of water per second during this period. ("Glacial Lake Agassiz: The northwestern outlet and paleoflood") Fisher has made Lake Agassiz one of the areas of his research and appears to be one of the authorities on this process.

My point about the possible initiation of a Heinrich event was not limited to a (much slower) discharge of water from Greenland. Rather, we are in an era showing a complex set of climatic changes that are strikingly similar to many of the changes that occur during Heinrich events, and other rapid climate changes yet to be classified. If the present climate change has been caused by human activity, it is probably the first of its kind (I leave open the absurd and improbable possibility of a pre-historic population explosion and massive use of campfires. SimIceAge, anyone? :) ).

Interference with thermohaline dynamics anywhere in the North Atlantic -- or even in other oceanic areas -- could have dramatic effects on the world's climate. Of course, the exact mechanisms remain unknown. We could be dealing with very delicately balanced climatic and oceanic processes, but at the same time, they would have to be robust enough to survive the ordinary fluctuations of a chaotic planetary heat "household".

I don't know that it is even probable that a high meltwater influx is required to damp thermohaline currents per se. A number of "chimneys" of water responsible for heat exchange off the North Sea have been observed to have just stopped in the last few years. Such phenomena were discovered in the late 1970s, which is when I began my sporadic reading in paleoclimatology. This made the news this past spring, and several articles cited Peter Wadhams of the Polar Ocean Physics Group (Cambridge). IIRC, the numbers given were twelve active heat chimneys at the outset, down to two now, a period of about a decade. (Sorry, I had no success finding the specific paper which led to the news item, and the scientific cruise reports are many and lengthy.)

5. Dynamics of the Earth's rotation and climate: I believe that your statement may come from Berger and Loutre, who think we are within a >50 kY interglacial period. On the other hand, Imbrie and Imbrie have made the opposite prediction, that we are in the beginning of a >23 kY cooling phase. (A. Berger, M.F. Loutre (2002). Climate: An exceptionally long interglacial ahead?, Science, 297(5585): 1287-1288. - and - J. Imbrie, J.Z. Imbrie (1980). Modeling the Climatic Response to Orbital Variations, Science, 207(1980/02/29): 943-953. Both are referenced at the Wikipedia Milankovitch cycles article.) It appears that they are each working with the compound cycles of the Earth's eccentricity, which is predicted to stay low beyond the next 100 kY. But there are a number of competing Milankovitch-like models now under consideration, so the issue is still open. And all such models have the problem that they can not take abrupt changes in the environment into consideration. (Richard A. Muller, Ice Ages and Astronomical Causes, online page. Muller's pages in general are full of absorbing reading.)

The risk of our interglacial ending still looks like an open issue. If we (geologists, that is) had better proxies, with a longer period of usability, we'd have a much better basis to work from -- obviously! But I think the best proxy ice core data we have is from the Lake Vostok studies which recently concluded. They go back about 450 kY. With Milankovitch cycles of over 100 kY, that's not nearly enough time to either draw long-range conclusions (e.g., our climate over the next 50 kY) or tease out the long cycles with better precision. But I am clearly on the thinner ice in stating that human forcing of climate could snap us into a new glacial period.

Thanks again for your post. My ever-decaying brain was quite happy for the workout!

--p!

[Odin2005]

10. LOL

"Thanks again for your post. My ever-decaying brain was quite happy for the workout!"

No problem, I just read an intresting book on the subject, Frozen Eath I think it's called. I also read the big, fat tome Coevolution of Earth and Life, a bit dated (late 80's) but still a good read for info on paleoclimatology.

[One_Life_To_Give]

11. Years before most notice.

To many in the developed world sea level changes will not be readily apparent until it is at least two feet. Many other things will be altered along the way. But until the normal astronomical high tides start topping their seawalls. The majority will be indifferent to the effects. Even recreational mariners may not notice a change of less than three inches.