Results from a new Greenland ice-core

[Daryl Habel]

To all,

An article in this week's (9 September) issue of NATURE, 431: 147-151.  This tells of a new Greenland ice-core, which should provide better detail for the beginning of the last Ice Age than what could be ascertained from previous ice-cores from Greenland .
---------------------
High-resolution record of Northern Hemisphere climate extending into the last interglacial period.

authored by: North Greenland Ice Core Project Members (Dahl-Jensen et al.)

Summary

Two deep ice cores from central Greenland, drilled in the 1990s, have played a key role in climate reconstructions of the Northern Hemisphere, but the oldest sections of the cores were disturbed in chronology owing to ice folding near the bedrock. Here we present an undisturbed climate record from a North Greenland ice core, which extends back to 123,000 years before the present, within the last interglacial period. The oxygen isotopes in the ice imply that climate was stable during the last interglacial period, with temperatures 5 °C warmer than today. We find unexpectedly large temperature differences between our new record from northern Greenland and the undisturbed sections of the cores from central Greenland, suggesting that the extent of ice in the Northern Hemisphere modulated the latitudinal temperature gradients in Greenland. This record shows a slow decline in temperatures that marked the initiation of the last glacial period. Our record reveals a hitherto unrecognized warm period initiated by an abrupt climate warming about 115,000 years ago, before glacial conditions were fully developed. This event does not appear to have an immediate Antarctic counterpart, suggesting that the climate see-saw between the hemispheres (which dominated the last glacial period) was not operating at this time.

For the journal Nature access to summary and full text for subscribers: CLICK HERE

There also is a related news story which appears today on the news@nature.com website.  Of special interest the NGRIP team also reported finding a fragment of plant matter they think might date back millions of years to when trees grew in Greenland.  
-------------------
Ice core reveals gentle start to last ice age
Mark Peplow
Traces of ancient life found beneath Greenland's ice sheet.

CLICK HERE FOR ENTIRE STORY
--------------------

An excerpt from the news story:

Life at the bottom

When the NGRIP team reached the bottom of the glacier last year, they got a surprise - liquid water, formed by Earth's heat melting the bottom of the glacier. "We were totally awed," says Dahl-Jensen. Although the melting had removed a few thousand years of climate record, it has also given the project an exciting new twist.

The team has found a fragment of plant matter - possibly bark - in the water, which may have lain under the ice for millions of years, since it was warm enough for trees to grow.

"It is unlikely to be contamination," says Mulvaney. "My suspicion is that they've got something that's been there since ice first formed on Greenland." Precise dating of the object could reveal when Greenland was first covered by ice, he adds, giving a glimpse even further back into our planet's climate history.

The researchers also found DNA in the water, although they have not been able to rule out contamination from the drilling equipment. They are now studying a fresh sample of this water taken with sterilized equipment for signs of ancient life - or perhaps even a community of microbes that is still living there today.

References

(1) Dahl-Jenson D., et al. Nature, 431, 147 - 151(2004).

(2) Wolff E., et al. Nature, 429. 623 - 628 (2004).

Regards,
Dar

[Dale Hoogeveen]

Hi Dar,

If the ice sheets show effects of different lattitudes,  does it follow that similar lattutides show different effects from presence or absence of the ice sheet?   That might affect  both how deeply glacial weather penetrates ahead of ice sheet advance (IOW for example does glacial weather advancing ahead of southward movement have decreasing effect with decreasing lattitude) and how far laterally as one moves off the ice at the same lattitude.  In both cases how well do uncovered portions maintain their pre-glacial temperature patterns (which does not necessarily deny some general cooling)?

This seems to suggest a remote possibility that non-glaciated portions of Europe during the last glacial period may not have been as arcticly harsh as they are often portrayed with perhaps less and less remote temperature effect as the ice sheet moved deeper into temperate lattitudes and an increasingly smaller band of acute temperature effect off the front and side edges.   This might also result in some crowding of displaced arctic faunal communities into increasingly temperate climates.

Sub glacial melt water also suggests that at least some patterns laid down by permafrost in areas that were covered  were formed under the ice sheet rather than ahead of it.

Dale 

To all,

An article in this week's (9 September) issue of NATURE, 431: 147-151.  This tells of a new Greenland ice-core, which should provide better detail for the beginning of the last Ice Age than what could be ascertained from previous ice-cores from Greenland .
---------------------
High-resolution record of Northern Hemisphere climate extending into the last interglacial period.

authored by: North Greenland Ice Core Project Members (Dahl-Jensen et al.)

Summary



For the journal Nature access to summary and full text for subscribers: CLICK HERE

There also is a related news story which appears today on the news@nature.com website.  Of special interest the NGRIP team also reported finding a fragment of plant matter they think might date back millions of years to when trees grew in Greenland. 
-------------------
Ice core reveals gentle start to last ice age
Mark Peplow
Traces of ancient life found beneath Greenland's ice sheet.

CLICK HERE FOR ENTIRE STORY
--------------------

An excerpt from the news story:


Regards,
Dar

[Daryl Habel]

Hi Dar,

If the ice sheets show effects of different lattitudes,  does it follow that similar lattutides show different effects from presence or absence of the ice sheet?  
(SNIP)
Sub glacial melt water also suggests that at least some patterns laid down by permafrost in areas that were covered  were formed under the ice sheet rather than ahead of it.

Dale

Hi Dale,

I don't have answers to your questions.  No access to the full text of the Nature article, so I don't know all of what they say.  But it has always been known that the ice cores previously drilled in Greenland were not of particularly good resolution for the Eemian period (the Last Interglacial, ca. 127-115 ka).  Also, the comparison between Greenland climate as recorded in the GRIP cores and European climate at comparable (and more southern) latitudes is not going to be an exact correlation.  There's still a lot of work to do here, regardless of what is said in the 5-page Nature article which, although I haven't read it, probably is more announcement of a superior resolution for the Eemian along with preliminary speculations (how much real scientific results can you report in 5 pages?).   I imagine future study of this new core will produce some interesting paleo-climatic scenarios, and possibly some theories relating to the present-day global warming issue, but it's probably a bit early to say what these will be.

Sub-glacial meltwater does suggest possible sub-glacial redepostion, in specific localities where this occurs,I agree.  But I don't think this is a new insight.

Poorly informed but interested,
Dar

 

[Dale Hoogeveen]

Hi Dar,

Not new ideas.  What is being found seems to make sense and I probably should have seen something of this nature at first glance, instead of having to step back and reexamine this.

I guess I caught myself thinking that a full arctic climate zone would precede a glacial advance into milder lattitudes, which, of course, isn't reasonable in the first place. 

I was over-simplifying the weather, which I expect a lot of others do also.

BTW having done some nursery work in the past, it seems to me that an advancing glacier should capture stems and seeds, a lot of which store very well frozen and many even need it to "ripen" enough to initiate the rooting of woody cuttings and for seed germination.  Some types of seeds actually need several winters and many hold viability indefinitely when frozen.  Might not a retreating glacier actually have occasionally replanted behind itself?  If it did happen, it was probably rare, of course, but would give some types a leg up on recolonization from any kind of remote refuge. 

This should work somewhat differently in a dynamic and moving ice sheet than in a permanent standing glacier.  The Greenland glacial sheet may be too old and too locally permanent to be as informative about this as one might like.

I know "no answers". <grin>  No problem, I always more questions that the ability to resolve them anyway, and take more potshots than the data probably warrants as well...

Dale

Hi Dale,

I don't have answers to your questions.  No access to the full text of the Nature article, so I don't know all of what they say.  But it has always been known that the ice cores previously drilled in Greenland were not of particularly good resolution for the Eemian period (the Last Interglacial, ca. 127-115 ka).  Also, the comparison between Greenland climate as recorded in the GRIP cores and European climate at comparable (and more southern) latitudes is not going to be an exact correlation.  There's still a lot of work to do here, regardless of what is said in the 5-page Nature article which, although I haven't read it, probably is more announcement of a superior resolution for the Eemian along with preliminary speculations (how much real scientific results can you report in 5 pages?).   I imagine future study of this new core will produce some interesting paleo-climatic scenarios, and possibly some theories relating to the present-day global warming issue, but it's probably a bit early to say what these will be.


Sub-glacial meltwater does suggest possible sub-glacial redepostion, in specific localities where this occurs,I agree.  But I don't think this is a new insight.

Poorly informed but interested,
Dar