PP026-03
Amazon Hydroclimate Response to Millennial and Orbital Scale Forcing
Thursday, 10 December 2020: 16:08
Virtual
Dylan Parmenter, University of Minnesota Twin Cities, Department of Earth & Environmental Sciences, Minneapolis, MN, United States, Francisco William Cruz Sr., Universidade de São Paulo, Instutit of geosciences, São Paulo, Brazil, Hai Cheng, Xi'an Jiaotong University, Institute of Global Environmental Change, Xi'an, China, Xianfeng Wang, Nanyang Technological University, Earth Observatory of Singapore, Singapore, Singapore, Augusto S Auler, Brazilian Karst Research Institute, Belo Horizonte, Brazil and R. Lawrence Edwards, University of Minnesota Twin Cities, Deptartment of Earth and Environmental Sciences, Minneapolis, MN, United States
Abstract:
The Amazon Lowlands provide an ideal locality to test the idea
1 that in a warming world wet regions should get wetter. In part to test this idea, we have extended the existing cave record from Paraiso Cave
2 (04
o04'S, 55
o27'W) beyond 45 ka. The full record now covers 70 ka, allowing us to investigate 9 additional millennial scale events, as well as events that correlate with the MIS 4/3 transition. The new record has δ
18O values ranging between -3 and -6‰ and for overlapping sections replicates the old record. The most prominent events in the extended record are a -1.5‰ shift, representing a pluvial anomaly that occurs between 47.0 and 48.9 ka, correlative with Heinrich Stadial 5, and a -1.7‰ shift accompanying the MIS 4/3 transition between 65 to 60 ka.
The new record extends the previously observed2 millennial-scale anti-phased relationship between Amazon precipitation on one hand, and Asian Monsoon precipitation and Greenland temperature on the other hand, with dry periods in China and cold periods in Greenland correlating with wet conditions at our study site. The anti-phase behavior on millennial timescales may be explained through changes in both in-situ and upstream convection generated by the Intertropical Convergence Zone, responding to changes in North Atlantic climate3. On orbital timescales, Amazon rainfall correlates more strongly with atmospheric CO2 than with insolation, in contrast to observations from elsewhere in South America. We observe a smaller shift in δ18O at the MIS 4/3 transition than was documented for the MIS 2/1 transition2, however both shifts are broadly proportional to correlative shifts in atmospheric CO2. Thus, the observations at both the MIS 4/3 and 2/1 transitions are consistent with the Held and Soden hypothesis1.
1Held, I. M., & Soden, B. J. (2006). Journal of Climate, 19, 5686–5699.
2Wang, X. F. et al. (2017). Nature, 541, 204–207.
3Chiang, J. C. H., & Bitz, C. (2005). Climate Dynamics, 25, 477–496.
