NAGT part deux

"Caffeine and Carbs" breakfast at Lamont-Doherty Earth Observatory, in their new science building, the Gary Comer building. Apparently Mr. Comer is a businessman who sailed through the northwest passage on a bet, that he wouldn't be able to do it. After completing it, he was apparently so impressed by the lack of ice blocking the passage, that he became very interested in climate. One of the results of that is then this new research facility. Most of the researchers haven't moved in yet, at least it looked like that to me, but there were several that were doing work while the conference was going on. I beleive that Dr. deMenocal's lab is going to be in this building also. Out of the blue, Dr. Green from the department showed up and we talked for a while. Then, possibly out of the same blue, Dr. Coke from Adelphi showed up. We talked for a while too. That was especially fortunate for me, because I didn't have the car for that trip and he offered me a ride on the Iron Mine trail trip, which I had been planning on going on. Dr. Green was attending a different trip. NAGT had prepared box lunches for the trip, but you had to pay for them, which is unusual, but probably a result of having to plan the whole thing on two month's notice.

After breakfast, Dr. Wally Broecker from LDEO gave a talk. Infact, it was the same talk he had given at the OSM 2008 meeting in Orlando, "Warning from the world's tiny Oceans (closed lake basins)." He started by considering Held's (Issac Held, Princeton) prediction that in a warming world, the tropics get wetter and the drylands get drier. Dr. Broecker reasoned that if thats what happens in a warming world, then should, in a cooling world, the tropics get drier and the drylands get wetter? He tested this by looking at the sizes of various pluvial (closed basin) lakes through the ages. He decided that the following equation applies:

A(basin)* hRfr = A(lake)hE (hR rainfall rate, fr runoff fraction, hE lake evaporation)

and that from this,

A(lake)/A(basin) = fr (hR/hE)

He refered to a 'mystery interval' between just before 18kya and 14kya where climate acts strangely. In this interval, the Southern ocean is warming, while ice coverage in the Northern hemisphere grows. He also stated that there was an increase in CO2, probably caused by the retreat of seaice in the Southern Hemisphere.

The ITCZ shifts southwards, because it follows heat across the globe (this is what it normally does in austral summers). This incidentally results in a weakening of monsoons. The biggest southwards push of the ITCZ is during the Mystery Interval.

Dry lakes are largest during the mystery interval, and large at the LGM. Dr. Broecker concluded that the ice volumes that existed during the ice ages do NOT obviate Held's prediction, and that drylands will infact get much dryer as the world warms.

He also, interestingly, stated that he wasn't too concerned anymore with shutdown of global thermohaline circulation, especially not by influx of fresh water into the North Atlantic. The Younger Dryas cooling that may have resulted from just such an effect would've required a great amount of water. Since there aren't giant reserves of ice today, Dr. Broecker observed, we're probably not going to have a massive influx of freshwater, even with melting at the poles, and shutting down THC. He also felt that the recent papers that claimed to have observed a shutdown of the Gulf Stream were just too short in duration to be able to call 'abnormal'. He figured you'd need a 30 year record or something like that on that level of detail to be able to rule of 'normal' cycles.


There was a break after the talk, and then we met for the saturday field trips. I went on a trip to the Iron Mine trail at the Sterling Forest Visitors center in NY. Dr. Gates of Rutgers lead the trip and passed out a trip guide booklet. The trail included a pre-revolution Iron Furnance which had been shut down in the 1760s, but then, at the command of none less than Washington himself was rebuilt and reopened to aid in the war. Afterwards, it was shutdown again. It reopened again much later, and ceased operations in the 1920s. Originally ore rock, charcoal, and limestone was carted to the Furnace, dumped into it, and then it was tapped at the bottom to release molten iron. In the closer to modern period, magnetite ore was actualy mined on location. Apparently the people that built the Furnace didn't know that there was in fact a large reserve of ore so close by. The remains of the more modern that shutdown in the 1920s are still there. Cables for the cable cars are strewn all around the cable house. We walked off the path and behind those remains and a little ways and came upon a small strip mine, with an entrance to another underground mine nearby in a depression of rocks, the organization had sealed a gate over the entrance to prevent anyone from entering, the interior of the mine if of course flooded anyway.
The magnetite in this location, Dr. Gates explained and pointed out, did not, as is usual, form by deposition within fractures of the surrounding rock. Rather, the source water leached into the surrounding carbonate rocks, and slowly replaced them such that now the magnetite has the relict structures of the carbonate.
The visitors center had very nice dioramas of the furnance and mine and the park in general. We also watched a short video wherein Dr. Gates, and a cartoon cave man (Dr. Gates was equally bewildered as the rest of us), described the geological history of the park. We started in the visitors center and ended there. One of the park rangers had relatively recently been able to acquire and trace back to the more modern mine an ore cart (apparently the person who had previously found it had been using it as a bbq), and also a part of the pre-revolutionary Furnace, some sort of iron flange that they thought was slotted into a beam as part of the Furnance, which was powered by a waterwheel.