Exploring the Impacts of Past Climate Change on Terrestrial Carbon Storage in the South American Tropics

EPA Grant Number: F13B20322
Title: Exploring the Impacts of Past Climate Change on Terrestrial Carbon Storage in the South American Tropics
Investigators: Fornace, Kyrstin
Institution: Woods Holes Oceanographic Institution
EPA Project Officer: Lee, Sonja
Project Period: August 1, 2014 through August 1, 2016
Project Amount: $84,000
RFA: STAR Graduate Fellowships (2013) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Fellowship - Oceanography , Fellowship - Earth Sciences

Objective:

The aim of this research is to characterize changes in the terrestrial storage time of plant-derived organic carbon during periods of distinct climate conditions over the last 20,000 years at two tropical South American sites, Lake Titicaca (Peru/Bolivia) and Cariaco Basin (Venezuela). These two sites have had very different climate histories since the last glacial period, allowing exploration of the effects of both hydrologic and temperature variability on the terrestrial carbon cycle in the tropics.

Approach:

Compound-specific radiocarbon analysis of vascular plant biomarkers in marine and lacustrine sediment cores will be used to determine the difference in age between these biomarkers and the sediment deposition age, which reflects the storage time of plant-derived organic carbon on land before transport to the sediment. Although terrestrial organic carbon is comprised of a wide variety of different compounds, the specific biomarkers to be used—leaf wax compounds—are found in soil and fresh leaf litter and thus serve as proxies for both labile and refractory subsets of biospheric organic carbon. Sediment deposition ages will be determined by radiocarbon dating of aquatic biomarkers that are produced and rapidly exported to the sediment. Approximately 10 sediment horizons from the late glacial period to the present will be targeted for analysis. These particular horizons will allow investigation of the impact of temperature increase and changes in precipitation from the glacial period to the Holocene, long-term precipitation trends during the Holocene and the effects of abrupt shifts in precipitation during the last deglaciation on terrestrial carbon storage.

Expected Results:

The results of small-scale studies have shown that warmer and wetter conditions tend to decrease the average storage time of organic carbon on land, both through faster respiration in the soil and increased erosion and river transport. The relationship between climate and the terrestrial carbon cycle in a large catchment area is likely more complex due to the many different processes operating within the catchment. However, by comparing trends in the terrestrial storage time of plant biomarkers at two sites with different climate histories, the imprints of past climate change might be identified. In the tropics, where precipitation changes tend to be more extreme than changes in temperature, hydrologic variability may be the key driver of changes in the terrestrial carbon cycle at both sites.

Potential to Further Environmental/Human Health Protection

Future climate change will likely have profound impact on human society, as well as on the global carbon cycle. Understanding the connection between climate change and the terrestrial carbon cycle is crucial for predicting future climate trends and shaping international policy on greenhouse gas emissions. This research will inform such efforts by providing the perspective of the impact of large climate changes in the past.

Supplemental Keywords:

carbon cycling, climate change, radiocarbon

Progress and Final Reports:

  • 2015
  • Final