New Research Opportunities in the Earth Sciences - New Research Opportunities in the Earth Sciences - page 75

satellites are being used to monitor changes in water storage at the basin-scale that
cannot be observed using any other technique (Famiglietti et al., 2011). Second, GPS
receivers in the EarthScope Plate Boundary Observatory (PBO) are being used to
measure critical environmental parameters such as soil moisture, snow depth, biomass
changes, and glacier retreat. These data are valuable to both climate scientists and
water managers for drought and flood prediction. These PBO studies demonstrate
how infrastructure developed for geophysical studies can simultaneously be used for
water cycle studies funded through the hydrological sciences within EAR, the
Division of Atmospheric and Geospace Sciences (AGS), and non-GEO directorates
such as the Directorate for Biological Sciences (BIO) and the Office of Polar
Programs (OPP).
The payoffs of such investments in data acquisition are potentially enormous
if the fluxes of energy, water, and materials within and through the critical zone can
be resolved and if fundamental insight can be provided into ecosystem and landscape
evolution and resilience. The data sets and understanding developed through such
measurements will form the basis for coupled systems models that allow study of
interactions and feedbacks between biological and physical processes in the critical
zone through assimilation of hydrological, meteorological, biogeochemical, and
geomicrobiological measurements.
Quantitative estimation of watershed carbon balance provides a compelling
example. Findings from the late 1980s to mid-1990s indicating that only ~30 percent
of the carbon dioxide released by fossil fuel burning stayed in the atmosphere, with
ocean uptake accounting for an additional ~30 percent, launched a stampede of
terrestrial ecosystem and surface Earth scientists to every biome on Earth to look for
the missing sink for the remaining 40 percent. However, after 15 years of effort, a
consensus has yet to emerge regarding the spatial distribution of, or the processes
responsible for, the 2 to 4 Pg C y -1 continental sink of the 1990s (Solomon et al.,
2007)—or the observation that continents were likely a net carbon source in the
2000s. One roadblock is that net ecosystem production (NEP) measured at local
scales does not often extrapolate well to larger scales (Ometto et al., 2005; Stephens
et al., 2007), very possibly due to lack of consideration of lateral export (Chapin et
al., 2006; Lovett et al., 2006) and the details of spatial and temporal variability. The
importance of full watershed-scale carbon balances is illustrated by the one published
study that accounted for both vertical carbon fluxes (via eddy covariance tower) and
lateral carbon exports via streams, demonstrating that Net Ecosystem Exchange
(NEE) went from a net sink of 0.278 Mg C ha -1 yr -1 to a net source of 0.083 Mg C ha -
1 yr -1 when lateral stream fluxes were accounted for (Aufdenkampe et al., 2011).
The integrated watershed studies needed to advance our understanding of the
critical zone is a distinctive feature of the CZO framework and their multidisciplinary
science teams. CZOs provide essential data sets and a coordinated community of
researchers who integrate hydrological, ecological, geochemical, and geomorphic
processes from mineral grain to watershed scales to illuminate the rich complexity of
interactions between the lithosphere, the pedosphere, the hydrosphere, the biosphere,
and the atmosphere. CZO sites are establishing infrastructure for the intensive data-
gathering effort required to support their science teams and the conceptual and
mathematical models they develop (see Box 2.9). The development of more diverse