In most climate model projections for the 21st century with moderate to high fossil fuel emissions, the Amazon becomes drier and Indonesia becomes wetter. Within the climate modeling community, this pattern of diverging tropical land precipitation had been attributed to the radiative effects of atmospheric carbon dioxide that influences ocean temperatures and atmospheric circulation. In a new analysis published in Nature Climate Change, Kooperman et al. show that the direct effect of rising carbon dioxide on tropical forests is responsible for much of this pattern. In response to rising CO2, plant stomates close, causing more absorbed radiation to dissipate in the form of sensible heat and less in the form of latent heat. In the Amazon, these changes in the surface energy budget suppress precipitation across lowland forests within the models, allowing more moisture contained in the tropical jet flowing from the Atlantic to reach the Andes. In Indonesia, greater sensible heating on land triggers a stronger land-sea breeze and moisture convergence over the islands of Sumatra and Borneo. This work suggests neotropical forests may be more vulnerable to climate warming, as they will have less available soil moisture to evaporatively cool. Higher levels of rainfall in Indonesia may make it easier to conserve tropical peatlands, but other important land management steps must be undertaken, including restoration work to remove canal networks.
Weiwei Fu’s paper published this week in Global Biogeochemical Cycles shows ocean oxygen minimum zones are poised for a wild ride over the next few centuries. First they will expand from warming, but then they may shrink far below current levels. Recovery of oxygen after 2200 does not necessarily bode well for ecosystems: the reversal in the hypoxia trend is driven by loss of nutrients from surface waters and decreases in marine productivity well below contemporary levels. The O2 recovers because the tropical ocean biosphere becomes more like a desert. This work is a nice illustration of a biological tipping point (one we don’t want to cross) and the value of exploring Earth system changes in deep future time!
Shane Coffield, a first year Ph.D. student in Earth System Science, was awarded a 2018 NSF Graduate Research Fellowship. Shane proposes to work on fire prediction and participates in the Machine Learning in Physical Sciences (MAPS) NSF training program. Congratulations to Shane for this prestigious award!
I am looking to hire 1-2 Ph.D. students and 1-2 postdoctoral scholars in my laboratory during 2018 and 2019.
For Ph.D. students, I am particularly interested in working with students on research topics related to the global carbon cycle and analysis of land cover change using land surface modeling and remote sensing techniques.
For postdoctoral scholars, I plan to hire someone in the area of high resolution terrestrial remote sensing. I also wish to hire someone interested in studying global carbon and water cycles using earth system modeling and data science approaches.
I particularly encourage women and underrepresented minority candidates to contact me and apply for these positions!
In a paper published in November of 2017, Dr. Yang Chen describes how ocean teleconnections during El Nino create a predictable pattern of drought and fire across different tropical continents. The work draws upon the +20 year record of burned area and fire emissions developed by researchers working on the Global Fire Emissions Database (GFED). Tropical forest fires more than doubled during El Nino events, with burning in equatorial Asia during autumn (Sept-Oct.) followed by elevated fire emissions in Southeast Asia, northern South America, and Central America during winter and spring, and the southern Amazon during the following summer. Since fire responses unfold in a predictable cascade, this information may improve seasonal forecasting systems for fire risk, and allow for improvements in ecosystem management. Lead times were long in the southern Amazon where land-atmosphere moisture coupling introduced time delays between soil moisture anomalies and surface humidity responses, and in Australia, where precipitation impacts on fuel amount added an additional time delay between El Nino onset and decreases in fire activity. The paper was discussed in a article by Cosmos Magazine.