Re: [asa] Subglacial Water System Moving Faster Than Previously Thought

On Feb 16, 2007, at 10:41 AM, Janice Matchett wrote:

> At 10:14 AM 2/16/2007, Rich Blinne wrote:
>
>> "..I'm sticking with my uh oh." ~ Rich
>
> @ Almost as if he anticipated a response such as yours, we have
> this comment (and one other one I like below it):
>
> "Since we've only observed this recently, we should assume that
> it's a new phenomenon, rather than something that's been going on
> for millions of years." [ :) ] ~ 3 posted on 02/15/2007
> 7:20:06 PM EST by 3niner http://freerepublic.com/focus/f-news/
> 1785619/posts?page=3#3

It's not the existence of the lakes that's the problem but the speed
of the motion and the leaks into the ocean. Ice falling into the
ocean does not raise sea level for the same reason ice cubes float on
water. Leaks into the ocean are a different story.

>
> "This is nice to know, but it has less importance due to the IPCC
> report downgrading the likeliness of Antarctic ice melting. The
> current IPCC report (only the executive report (PDF) has been
> released) notes that Antarctica ice loss should be minimal until
> after 2100 because the ice is too cold and the models predict
> increased precipitation in Antarctica.

TAR said it was "very unlikely" that there would be Antarctic ice
loss in the Twenty-First Century. How is this downgrading it?

> Due to this (and the Greenland ice loss downgrade) most models now
> only predict a 20 to 50 cm rise in ocean levels due to the seawater
> heating up and glaciers melting. Al Gore is going to feel sad since
> his 20 ft sea level rise now looks incredibly unlikely even by the
> UN. The IPCC report does note that dynamic ice loss events could
> change this forecast but since they haven't demonstrated any likely
> candidates yet (perhaps they are in the full report) I would have
> to assume that they are classifying those types of events in the
> "what if" category (like what if someone decided to nuke Antarctica
> 1000 times).

He cannot have it both ways. He wants to lean on models of glacier
melting that consistently underestimate but not the temperature
models that fit the data nicely. It is good to be skeptical of the
sea level models because they simply put are not very good. So, let's
see what the draft report said about what's currently being measured
instead of the models:

•
> Snow cover has decreased in most regions, especially in spring.
> April Northern Hemisphere (NH) snow cover observed by satellite
> decreased during 1966–2004 by 0.5 × 106 km2 per decade, or about 5%
> in total. NH snow cover decreased in every month but November and
> December. In the Southern Hemisphere (SH), the small number of long
> records or proxies mostly shows either decreases or no changes in
> the past 40+ years. Where snow cover or snow pack decreased,
> temperature often dominates; where snow increased, precipitation
> almost always dominates. For example, NH April snow cover extent is
> significantly correlated (r = –0.68) with 40–60°N April
> temperature, and declines in the mountains of western North America
> and in the Swiss Alps are largest at low elevations.
>
>
> • Freeze-up and break-up dates for river and lake ice exhibit
> considerable spatial variability (with some regions showing trends
> of opposite sign). Averaged over available data for the NH,
> spanning the past 150 years, freeze-up date has occurred later at a
> rate of 5.8 ± 1.9 days per century, while the break-up date has
> occurred earlier at a rate of 6.5 ± 1.4 days per century.
>
>
> • Satellite data indicate a continuation of the roughly 2.7 ± 0.7%
> per decade decline in annual mean Arctic sea-ice extent since 1978.
> The decline for summertime extent is larger than for wintertime,
> with the summer minimum declining at a rate of about 7.4 ± 2.9% per
> decade. Other data indicate that the summer decline began around
> 1970. Similar observations in the Antarctic reveal larger inter-
> annual variability but no consistent trends.
>
>
> • Submarine-derived data for the central Arctic indicate a
> reduction in sea-ice thickness of about 1m from 1987 to 1997. Model-
> based reconstructions suggest an Arctic-wide reduction of 0.6 to
> 0.9 m over the same period. Large-scale trends prior to 1987 are
> ambiguous.
>
>
> • Mass loss of glaciers and ice caps is estimated to be 0.51 ± 0.32
> mm in sea level equivalent (SLE) per year between 1961 and 2003,
> and 0.81 ± 0.43 mm SLE per year between 1993 and 2003. The late
> 20th century glacier wastage is likely a response to post-1970
> warming. Strongest mass losses per unit area are observed in
> Patagonia, Alaska and NW USA/SW Canada. Because of the
> corresponding large areas, the biggest contributions to sea level
> rise come from Alaska, the Arctic, and the Asian high mountains.
>
>
> • Taken together, the ice sheets in Greenland and Antarctica are
> shrinking. Thickening in central regions of Greenland is more than
> offset by increased melting near the coast. Some outlet glaciers,
> which drain ice from the interior, are accelerating in both
> Greenland and Antarctica. Assessment of the data and techniques
> suggests a mass balance of the Greenland Ice Sheet of between +25
> and –60 Gt (–0.07 to 0.17 mm SLE) per year from 1961–2003, and –50
> to–100 Gt (0.14 to 0.28 mm SLE) per year from 1993–2003, with even
> larger losses in 2005. Estimates for the overall Antarctic ice-
> sheet mass balance range from +100Gt to –200 Gt (–0.28 to 0.55 mm
> SLE) per year for 1961–2003, and from +50 Gt to –200 Gt (–0.14 to
> 0.55 mm SLE) per year for 1993–2003. Acceleration of mass loss may
> have occurred, but not so dramatically as in Greenland.
>
>
> • Permafrost temperature has increased by up to 3°C since the 1980s
> in the Arctic. The permafrost base is thawing at a rate ranging
> from 0.02 m/year in Alaska to 0.4 m/year on the Tibetan Plateau.
> Permafrost degradation is leading to widespread changes in land
> surface characteristics and drainage systems
>
> The maximum extent of seasonally frozen ground has decreased by
> about 7% in the NH, and its maximum depth has decreased about 0.3 m
> in Eurasia since the mid-20th century. In addition, maximum
> seasonal thaw depth has increased about 0.2m in the Russian Arctic.
> Onset dates of thaw in spring and freeze in autumn advanced five to
> seven days in Eurasia from 1988–2002, leading to an earlier growing
> season but no change in duration.
>
>
> • Results summarized here indicate that the total cryospheric
> contribution to sea level change ranges from –0.2 to 1.5 mm per
> year between 1961–2003, and from 0.4 to 2.1 mm per year between
> 1993 and 2003, at rates that increased during the period primarily
> due to increasing losses from mountain glaciers and ice caps.
> Assuming a midpoint-mean ± uncertainties and Gaussian error
> summation of estimates for glaciers and ice sheets, a total
> cryospheric contribution of 1.2 ± 0.6 mm SLE per year is derived
> for 1993–2003.
>

Page 4-2, 4-3 AR4 Draft Report

>
> I can't wait until the full IPCC report comes out because I am
> trying to figure out what they are talking about with the 1.6 W/m²
> radiative forcing (with 1-sigma ranges apparently from 0.6 W/m² to
> 2.4 W/m²). It appears to me that their 2-sigma values would overlap
> 0 W/m² which is probably from where the 90% probability that they
> listed comes from (with 10% less than 0 W/m²). If this is the case
> then they are dramatically overstating the importance of the
> calculated radiative forcing in the same way that stating that the
> gravitational acceleration was 9.8 m/s² (with 1 sigma values from
> 4.0 m/s² to 16.0 m/s²) would be too imprecise a measurement of g to
> be of great use." ~ 4 posted on 02/15/2007 8:21:39 PM EST by burzum
> http://freerepublic.com/focus/f-news/1785619/posts?page=4#4

e'He is obviously is not familiar with the IPPC report because there
won't be 2-sigma values.

> The quoted uncertainty range is roughly equivalent to a one-sigma
> value uncertainty from available results.

Page 2-66, Draft AR4 report.

What Janice bolded:

> From December 2003 to December 2005, MODIS captured these two
> images showing a draw down of water in a subglacial lake (left)and
> the rise of water in the same subglacial lake (right). Color coded
> ICESat tracks across both images indicate rises and falls in the
> elevation of the lake's water. (Credit: NASA)
>
What I bolded:
>
> In recent years, scientists have discovered more than 145
> subglacial lakes, a smaller number of which composes this "plumbing
> system" in the Antarctic. Bindschadler and Fricker; Ted Scambos of
> the National Snow and Ice Data Center in Boulder, Colo.; and
> Laurence Padman of Earth and Space Research in Corvallis, Ore.;
> observed water discharging from these under-ice lakes into the
> ocean in coastal areas. Their research has delivered new insight
> into how much and how frequently these waterways "leak" water and
> how many connect to the ocean.

It's these leaks that are a cause for concern.
>

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Received on Sun Feb 18 17:36:41 2007