v2 BGC and Energy Research

Uptake of CO2 by land and ocean ecosystems determines how much atmospheric CO2 concentrations increase due to emissions from combustion and other human activities. In turn, the efficiency of ecosystems in sequestering carbon responds to changes in climate and CO2 concentration.

The v2 biogeochemistry experiment seeks to answer this question:


What are the implications of different energy futures for the biogeochemical cycle through changes in land use land cover, water availability, and extreme events?

A major source of uncertainty in projecting Earth system changes beyond mid-century is how different energy futures perturb atmospheric composition and LULC, which in turn alter temperature, precipitation, and extreme events. In an energy future under RCP8.5, annual mean temperature over the U.S. is projected to increase by about 3.2oC to 6.6oC in 2070-2099 relative to 1976-2005 (Vose et al., 2017). Accompanying the warming is a significant increase in the frequency and intensity of heat waves. Increased evapotranspiration may lead to soil drying throughout North America (Wehner et al., 2017). In the western U.S., rising temperature and increases in vapor pressure deficit enhance fuel aridity, leading to an increase in forest fire areas (Abatzoglou and Williams, 2016). At high latitudes, warming may foster microbial decomposition of organic material previously frozen in permafrost to increase CO2 and methane release to the atmosphere (Koven et al., 2015). Wildfires, tree mortality, and thawing of permafrost could significantly reduce the carbon storage over land.

Increased air temperature increases sea surface temperatures and reduces ocean carbon uptake (Rhein et al., 2013), while increased CO2 concentration leads to ocean acidification (Bopp et al., 2013). Atmospheric deposition of nitrogen can increase biological productivity of oceans (Bonan and Doney, 2018), while changes in atmospheric composition due to fires and dust loading due to drought affect the nutrient budget for marine ecosystems.

As energy production and use perturb the environment, the latter will, in turn, affect energy pathways. For example, warmer temperatures will increase energy use for air conditioning during the summer months (Zamuda, 2018). Rising stream temperature and changes in water availability may reduce the generating capacity of thermoelectric power plants via changes in the supply and demand for surface water cooling (van Vliet et al., 2016). Changes in the timing and amount of streamflow can affect hydropower production. Energy supply from renewable resources such as winds and solar radiation may also be affected by changes in the environment (Karnauskas et al., 2018). Changes in water availability can also significantly influence bioenergy production and amplify water scarcity (Hejazi et al., 2015). Changes in temperature, precipitation and CO2 concentrations can alter crop yields (Rosenzweig et al., 2014) and LULC (Nelson et al., 2014), with implications for bioenergy use (Calvin et al., 2013; Kyle et al., 2014). Lastly, changes in extreme events such as hurricanes and storm surges, floods and droughts, heat waves, and strong winds may disrupt energy production and use.

Interactions among the energy, water, and biogeochemical cycles have the potential to amplify differences in climate outcomes along different pathways. Such differences will in turn alter the energy system in myriad ways as climate influences energy production and use. To address the v2 biogeochemical cycle science question requires an understanding of the complex interactions across all physical and biogeochemical components of the human-Earth systems. This poses a formidable challenge in Earth system modeling that the project will only be able to partly address with the v2 model features discussed below. To further understand the impacts of different energy futures, the project plans next generation model development to address a similar but expanded biogeochemical cycle science question in v3/v4.

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