Gunung Mulu Caves as Climate Recorders
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A presentation I delivered at a Gunung Mulu National Park staff meeting on May 18, 2016. A handy overview of some of our lab's key findings from our extended research on Borneo caves.
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Gunung Mulu Caves as Climate Recorders
- 1. Gunung Mulu Caves as Climate Recorders Kim Cobb, Georgia Tech Jess Adkins, Caltech Jud Partin, UT Austin Nele Meckler, NIO David Lund (Sang), UConn Jessica Moerman, U. Maryland Stacy Carolin, Oxford Shelby Ellis, Georgia Tech • Paleoclimate Research • GeorgiaTech • Cobb Lab
- 2. With many thanks to: Brian Clark, Manager, Gunung Mulu National Park Syria Lejau, Senior Guide, Gunung Mulu Jenny Malang, Senior Guide, Gunung Mulu Andrew Tuen, Professor, UNIMAS And with permits from: Sarawak Forestry Sarawak Planning Unit Malaysia Economic Planning Unit Moerman et al., GRL 2014
- 3. Mulu is FAMOUS for its climate records Longest cave dripwater collection in the world. (11yrs) Longest daily rainwater collection in the world. (10yrs) One of the longest, most replicated stalagmite climate records in the world.
- 4. How do we make a climate record at Mulu?
- 5. 1. rain 2. soil = high CO2 3. dissolve limestone (CaCO3) 4. degas CO2 5. precipitate speleothem CLIMATE
- 6. 1. rain 2. soil = high CO2 3. dissolve limestone (CaCO3) 4. degas CO2 5. precipitate speleothem Rainwater studies Kim Cobb et al., 2007 Jessica Moerman et al., 2013 Dripwater studies Kim Cobb et al., 2007 Jessica Moerman et al., 2014 Stalagmite studies Jud Partin et al., 2007 Nele Meckler et al., 2012 Stacy Carolin et al., 2013 Stacy Carolin et al., 2014 Nele Meckler et al., 2015 Sang Chen et al., 2016 CLIMATE
- 7. 1. Climate changes the “flavor” of the rainwater 2. The flavor of the drips = the flavor of the rainwater 3. The flavor of the stalagmites = the flavor of the drips 4. So the stalagmites record climate (wet/dry periods)
- 8. What is this “flavor”? Water (H2O) is made of Hydrogen and Oxygen.
- 9. What is this “flavor”? Water (H2O) is made of Hydrogen and Oxygen. 99.8% of Oxygen atoms have 8 protons + 8 neutrons = 16 0.2% of Oxygen atoms have 8 protons + 10 neutrons = 18
- 10. What is this “flavor”? Water (H2O) is made of Hydrogen and Oxygen. 99.8% of Oxygen atoms have 8 protons + 8 neutrons = 16 0.2% of Oxygen atoms have 8 protons + 10 neutrons = 18 “flavor” = changes in number of 18O vs 16O isotopes Rainfall in every city in the world has a different value, depending on the temperature, winds, cloud types, etc.
- 11. What is this “flavor”? Water (H2O) is made of Hydrogen and Oxygen. 99.8% of Oxygen atoms have 8 protons + 8 neutrons = 16 0.2% of Oxygen atoms have 8 protons + 10 neutrons = 18 “flavor” = changes in number of 18O vs 16O isotopes Rainfall in every city in the world has a different value, depending on the temperature, winds, cloud types, etc. At Mulu, dry periods and wet periods have a different oxygen isotope value.
- 12. What is this “flavor”? Water (H2O) is made of Hydrogen and Oxygen. 99.8% of Oxygen atoms have 8 protons + 8 neutrons = 16 0.2% of Oxygen atoms have 8 protons + 10 neutrons = 18 “flavor” = changes in number of 18O vs 16O isotopes Rainfall in every city in the world has a different value, depending on the temperature, winds, cloud types, etc. At Mulu, dry periods and wet periods have a different oxygen isotope value. We can measure these changes in rainfall, dripwater, and stalagmites in my lab at Georgia Tech.
- 14. ical Research Letters 10.1002/2014G WET DRY (DripwaterOxygen Isotopes) DRIPWATERS AT MULU WIND FAST WIND SLOW LANG’S Moerman et al., 2014
- 15. While the autogenic recharge model reproduces the timing of L2 dripwater δ18 O minima and maxima, it overestimates the amplitude of the drip’s δ18 O variations (Figure 2). Amount-weighted rainfall δ18 O averaged over the previous 42 weeks (~10months) best reflects the timing of dripwater δ18 O maxima and minima observed in L2 (R = 0.84), but the predicted variations are roughly 1‰ higher than observed (Figure 2). This suggests that the flow pathway to this drip site is more complicated than that feeding WF and WS. L2’s amplitude attenuation suggests a likely contribution from a second, well- mixed reservoir, which we model using a bivariate mixing model, XM ¼ XA 1 À fBð Þ þ XBfB (1) where XA is the isotopic composition of Reservoir A, XB is the isotopic composition of Reservoir B, and fB is the mixing parameter. Modeled dripwater δ18 O simulated by the autogenic recharge model with an ~10 month residenceFigure 2. Observed dripwater δ 18 O (circles) for drips WF (orange), WS (blue), 18 Conclusions: It takes 3-4 months for rainfall to move through Wind Cave It takes 10 months for rainfall to move through Lang’s Cave, but there is a second, slower source too (>3yrs). Average of rainfall oxygen isotopes over previous 3 months Observed dripwater oxygen isotopes
- 16. We use Uranium and Thorium chemistry to date the stalagmites, back to 550,000 yrs. We use two types of stalagmites: 1. Fallen (99% of our collection) 2. Drill cores from dripping stalagmites (white epoxy tops), cover recent past Most stalagmites are growing SLOW. 1mm growth in 100-1000yrs Fastest stalagmites are in Drunken Forest. 1mm growth in 5-10yrs Oldest stalagmites are in White Rock and Secret Chamber (~1.5 million yrs old)
- 17. Different colors are different Mulu stalagmites. They all tell the same story about climate through time! Carolin et al., 2016 Age (thousands of years before present) Hulu Cave, China1 Tropical Pacific Ocean Temp2 Atmospheric CO2 3
- 18. Mulu records give us many clues about the tropical climate system. dry dry dry dry Ex: Driest times at Mulu occur early in the transitions out of Ice Ages. We don’t know why, but we are working on it! Age (thousands of years before present) warm coldcold warm
- 20. Other paleoclimate records shown in slides 17-18: 1 Hulu/Sanbao stalagmite δ18O records Wang et al., 2001; Wang et al., 2008; Cheng et al., 2009 2 Marine sediment Mg/Ca SST records (Lea et al., 2000; 2004) 3 Vostok/EPICApCO2 record (Petit et al., 1999; EPICA, 2006)