Browsing by Author "Raymond, Peter"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Inland Water Greenhouse Gas Budgets for RECCAP2: 1. State-Of-The-Art of Global Scale Assessments
    Lauerwald, Ronny; Allen, George H.; Deemer, Bridget R.; Liu, Shaoda; Maavara, Taylor; Raymond, Peter; Alcott, Lewis; Bastviken, David; Hastie, Adam; Holgerson, Meredith A.; Johnson, Matthew S.; Lehner, Bernhard; Lin, Peirong; Marzadri, Alessandra; Ran, Lishan; Tian, Hanqin; Yang, Xiao; Yao, Yuanzhi; Regnier, Pierre (American Geophysical Union, 2023-05-05)
    Inland waters are important emitters of the greenhouse gasses (GHGs) carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) to the atmosphere. In the framework of the 2nd phase of the REgional Carbon Cycle Assessment and Processes (RECCAP-2) initiative, we review the state of the art in estimating inland water GHG budgets at global scale, which has substantially advanced since the first phase of RECCAP nearly 10 years ago. The development of increasingly sophisticated upscaling techniques, including statistical prediction and process-based models, allows for spatially explicit estimates that are needed for regionalized assessments of continental GHG budgets such as those established for RECCAP. A few recent estimates also resolve the seasonal and/or interannual variability in inland water GHG emissions. Nonetheless, the global-scale assessment of inland water emissions remains challenging because of limited spatial and temporal coverage of observations and persisting uncertainties in the abundance and distribution of inland water surface areas. To decrease these uncertainties, more empirical work on the contributions of hot-spots and hot-moments to overall inland water GHG emissions is particularly needed.
  • Thumbnail Image
    Seasonal variability of organic matter composition in an Alaskan glacier outflow: insights into glacier carbon sources
    Spencer, Robert G. M.; Vermilyea, Andrew; Fellman, Jason B.; Raymond, Peter; Stubbins, Aaron; Scott, Durelle T.; Hood, Eran W. (IOP Publishing, 2014-05-08)
    Glacier ecosystems are a significant source of bioavailable, yet ancient dissolved organic carbon (DOC). Characterizing DOC in Mendenhall Glacier outflow (southeast Alaska) we document a seasonal persistence to the radiocarbon-depleted signature of DOC, highlighting ancient DOC as a ubiquitous feature of glacier outflow. We observed no systematic depletion in Δ¹⁴C-DOC with increasing discharge during the melt season that would suggest mobilization of an aged subglacial carbon store. However, DOC concentration, δ¹³C-DOC, Δ¹⁴C-DOC and fluorescence signatures appear to have been influenced by runoff from vegetated hillslopes above the glacier during onset and senescence of melt. In the peak glacier melt period, the Δ¹⁴C-DOC of stream samples at the outflow (−181.7 to −355.3‰) was comparable to the Δ¹⁴C-DOC for snow samples from the accumulation zone (−207.2 to −390.9‰), suggesting that ancient DOC from the glacier surface is exported in glacier runoff. The pre-aged DOC in glacier snow and runoff is consistent with contributions from fossil fuel combustion sources similar to those documented previously in ice cores and thus provides evidence for anthropogenic perturbation of the carbon cycle. Overall, our results emphasize the need to further characterize DOC inputs to glacier ecosystems, particularly in light of predicted changes in glacier mass and runoff in the coming century.