Dust flux, Vostok ice core

Dust flux, Vostok ice core
Two dimensional phase space reconstruction of dust flux from the Vostok core over the period 186-4 ka using the time derivative method. Dust flux on the x-axis, rate of change is on the y-axis. From Gipp (2001).

Saturday, January 18, 2020

The History of the East Asia Monsoon

So I went to Washington DC last week for the AGU Chapman Conference on the East Asian monsoon. I found it to be a very rewarding conference, and even learned a bit about navigating around Washington on transit, as I was on a limited budget.

The conference was in AGU headquarters, which is near to Dupont Circle.


Not all that far from the Mall, although I didn't visit this time.


Speaking of scientists . . .

I was speaking during the opening session, which was about climate dynamics (and its role on the changes in monsoonal strengths through geologic history). A major dynamic role has been the rise of the Himalayan mountains and the Tibetan Plateau during the period of interest, and there is still a lot of debate about the importance of these tectonic events on the development of the monsoon. Some of the modeling studies suggest that the mountains only change the specific location of the rainfall, and that monsoon behaviour may occur even if there were no continents at all.

My work was based on analysis of global to regional proxy data sets, and has been summarized in all these places. Unfortunately, due to limited time, after working through the phase space reconstructions, I had to rush through the statistical computation part, and wasn't certain whether any of the message made it to the audience ungarbled. Fortunately, I was able to learn that at least some members of the audience understood the message.

The afternoon sessions were all about paleoceanographic records of the monsoon. Over the past decade, the International Ocean Discovery Program (IODP, formerly ODP and DSDP) has put down a number of boreholes in the Indus and Bengal Fans, and other boreholes in the Huang He fan and the Sea of Japan also provide useful records of at least some parts of the monsoon. The records I studied were generally global in scope--these other records allow for regional variations to be studied.

The next day's sessions dealt with continental environments (a common issue was the change in photosynthetic pathways of plants in response to environmental change during the Miocene) and records of continental erosion. Erosion is important because either rising mountains or increased rainfall will lead to increased erosion.

The last session was on modeling the effects of tectonic uplift as well as changes in the timing of the uplift, because there is still some disagreement about when the Tibetan Plateau was formed. I mean disagreement between it being less than 10 million years ago to more than 40 million years ago, which is a significant difference of opinion for something so recent.

The last portion of the conference was to break up into groups for focussed discussions on topics of interest leading to the testing of several hypotheses proposed at the start of the conference. I started off in the wrong room, so I was  with the tectonic modeling people rather than the climate modeling people, but was still able to ask about whether anyone had successfully had chaos appear in their model output. Results were inconclusive.

For the second group meeting I joined the combined discussion between the climate modelers and the paleoceanographic records group. Over the course of the discussion I eventually managed to come up with a proposal. See if the modelers observe chaos, and see if they can tell which style of chaos they have. Such chaos will be manifested as spatial variability in some climate effects, such as the location of the maximum rainfall. The models may have the type of spatial variability modeled correctly, but the specific timing of variations will be incorrect. That spatial variability will be recorded in the widely spaced paleoceanographic records which already exist. They type of chaos observed in the models will tell us what to look for in the cores; from the cores we can obtain the correct timing of the modeled chaotic spatial variations of the monsoon system.


Exiting the Metro Station at Dupont Circle

I wasn't sure how the last part of the conference would go--early on, many of the old hands were of the opinion that nothing ever comes from these things. But I thought it was pretty rewarding, particularly as it was during these sessions that I came to realize that people felt that whatever I was doing was worthwhile.

Alone in my corner of the world, I had never been sure.



Night flight back to Toronto

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