- #1
Andre
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I think I said before that the recent glacial era, the late Pleistocene is actually a string of riddles. One of them is the Mystery interval. As the ice core indications in Antarctica suggested a clear warming around 19-18,000 years ago, the ice cores in Greenland did not show anything. On the contrary, the proxies for temperature appeared to dip at 17,500 years until a very sudden jump up at 14,500 years ago. Originally known as the 'Oldest Dryas' it's now the Mystery Interval, especially because detailed studies on areas give conflicting results (Denton et al 2006)*
So here is a fresh article about the Mystery Interval:
Carlie Williams, Benjamin P. Flower and David W. Hastings, 2012, Seasonal Laurentide Ice Sheet melting during the "Mystery Interval" (17.5-14.5 ka), Geology, published online on 9 August 2012 as doi:10.1130/G33279.1
First impression is that if the Younger Dryas is equally enigmatic, how can you endorse an meltwater rerouting hypothesis, in the face of several conflicting evidence (more later) and other ideas?
However I'm going to read it carefully, maybe we find a gem.
*Denton G.H., Broecker, W.S. and Alley, R.B., 2006: The mystery interval 17.5 to 14.5 kyrs ago, PAGES news, 2: 14-16.
So here is a fresh article about the Mystery Interval:
Carlie Williams, Benjamin P. Flower and David W. Hastings, 2012, Seasonal Laurentide Ice Sheet melting during the "Mystery Interval" (17.5-14.5 ka), Geology, published online on 9 August 2012 as doi:10.1130/G33279.1
ABSTRACT
The last deglaciation in the Northern Hemisphere was interrupted by two major stadials, the so-called “Mystery Interval” (17.5–14.5 ka) and the Younger Dryas (12.9–11.7 ka). During these events, the North Atlantic region was marked by cold surface conditions, yet simultaneous glacier and snowline retreat. Rerouting of Laurentide Ice Sheet meltwater from the Gulf of Mexico to an eastern or northern spillway may have reduced meridional overturning circulation at the onset of the Younger Dryas. However, this hypothesis has not been tested for the Mystery Interval. Paired Mg/Ca and 18O measurements on foraminifera
from laminated Orca Basin sediments in the Gulf of Mexico, constrained by 35 14C dates, document the timing of meltwater input with subcentennial resolution. Isolating the 18O of seawater (termed 18OGOM) reveals three major melting episodes from ca. 17.5 ka until
12.9 ka, followed by a rapid cessation, consistent with meltwater rerouting at the onset of the Younger Dryas. Conversely, inferred meltwater flow to the Gulf of Mexico during the Mystery Interval does not support a simple routing event, but is consistent with glacier and snowline retreat. We suggest that summer melting of Northern Hemisphere ice sheets during this stadial may have been an important mechanism for enhanced winter sea-ice formation, hypercold winter conditions, and enhanced seasonality in the North Atlantic region.
First impression is that if the Younger Dryas is equally enigmatic, how can you endorse an meltwater rerouting hypothesis, in the face of several conflicting evidence (more later) and other ideas?
However I'm going to read it carefully, maybe we find a gem.
*Denton G.H., Broecker, W.S. and Alley, R.B., 2006: The mystery interval 17.5 to 14.5 kyrs ago, PAGES news, 2: 14-16.