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Title: Detecting regional patterns of changing CO 2 flux in Alaska

Abstract

With rapid changes in climate and the seasonal amplitude of carbon dioxide (CO 2) in the Arctic, it is critical that we detect and quantify the underlying processes controlling the changing amplitude of CO 2 to better predict carbon cycle feedbacks in the Arctic climate system. We use satellite and airborne observations of atmospheric CO 2 with climatically forced CO 2 flux simulations to assess the detectability of Alaskan carbon cycle signals as future warming evolves. We find that current satellite remote sensing technologies can detect changing uptake accurately during the growing season but lack sufficient cold season coverage and near-surface sensitivity to constrain annual carbon balance changes at regional scale. Airborne strategies that target regular vertical profile measurements within continental interiors are more sensitive to regional flux deeper into the cold season but currently lack sufficient spatial coverage throughout the entire cold season. Thus, the current CO 2 observing network is unlikely to detect potentially large CO 2 sources associated with deep permafrost thaw and cold season respiration expected over the next 50 y. In conclusion, although continuity of current observations is vital, strategies and technologies focused on cold season measurements (active remote sensing, aircraft, and tall towers) andmore » systematic sampling of vertical profiles across continental interiors over the full annual cycle are required to detect the onset of carbon release from thawing permafrost.« less

Authors:
 [1]; ORCiD logo [2];  [2];  [3];  [4];  [5];  [6];  [7];  [8]
  1. California Inst. of Technology (CalTech), Pasadena, CA (United States). Jet Propulsion Lab.; Univ. of California, Los Angeles, CA (United States). Joint Inst. for Regional Earth System Science and Engineering
  2. Harvard Univ., Cambridge, MA (United States). Dept. of Earth and Planetary Sciences; Harvard Univ., Cambridge, MA (United States). Harvard School of Engineering and Applied Sciences
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Climate and Ecosystem Sciences Division
  4. National Oceanic and Atmospheric Administration (NOAA), Boulder, CO (United States). Earth System Research Lab.; Univ. of Colorado, Boulder, CO (United States). Cooperative Inst. for Research in Environmental Sciences
  5. National Center for Atmospheric Research, Boulder, CO (United States). Climate and Global Dynamics Lab.
  6. Harvard Univ., Cambridge, MA (United States). Dept. of Earth and Planetary Sciences; Colorado State Univ., Fort Collins, CO (United States). Dept. of Atmospheric Science
  7. Dalhousie Univ., Halifax, NS (Canada). Dept. of Physics and Atmospheric Science
  8. California Inst. of Technology (CalTech), Pasadena, CA (United States). Jet Propulsion Lab.
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); National Aeronautic and Space Administration (NASA)
OSTI Identifier:
1259729
Alternate Identifier(s):
OSTI ID: 1379513
Grant/Contract Number:
AC02-05CH11231; FC03-97ER62402; PLR-1304220
Resource Type:
Journal Article: Published Article
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 113; Journal Issue: 28; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; carbon cycle; permafrost thaw; climate; Earth system models; remote sensing

Citation Formats

Parazoo, Nicholas C., Commane, Roisin, Wofsy, Steven C., Koven, Charles D., Sweeney, Colm, Lawrence, David M., Lindaas, Jakob, Chang, Rachel Y. -W., and Miller, Charles E. Detecting regional patterns of changing CO2 flux in Alaska. United States: N. p., 2016. Web. doi:10.1073/pnas.1601085113.
Parazoo, Nicholas C., Commane, Roisin, Wofsy, Steven C., Koven, Charles D., Sweeney, Colm, Lawrence, David M., Lindaas, Jakob, Chang, Rachel Y. -W., & Miller, Charles E. Detecting regional patterns of changing CO2 flux in Alaska. United States. doi:10.1073/pnas.1601085113.
Parazoo, Nicholas C., Commane, Roisin, Wofsy, Steven C., Koven, Charles D., Sweeney, Colm, Lawrence, David M., Lindaas, Jakob, Chang, Rachel Y. -W., and Miller, Charles E. Mon . "Detecting regional patterns of changing CO2 flux in Alaska". United States. doi:10.1073/pnas.1601085113.
@article{osti_1259729,
title = {Detecting regional patterns of changing CO2 flux in Alaska},
author = {Parazoo, Nicholas C. and Commane, Roisin and Wofsy, Steven C. and Koven, Charles D. and Sweeney, Colm and Lawrence, David M. and Lindaas, Jakob and Chang, Rachel Y. -W. and Miller, Charles E.},
abstractNote = {With rapid changes in climate and the seasonal amplitude of carbon dioxide (CO2) in the Arctic, it is critical that we detect and quantify the underlying processes controlling the changing amplitude of CO2 to better predict carbon cycle feedbacks in the Arctic climate system. We use satellite and airborne observations of atmospheric CO2 with climatically forced CO2 flux simulations to assess the detectability of Alaskan carbon cycle signals as future warming evolves. We find that current satellite remote sensing technologies can detect changing uptake accurately during the growing season but lack sufficient cold season coverage and near-surface sensitivity to constrain annual carbon balance changes at regional scale. Airborne strategies that target regular vertical profile measurements within continental interiors are more sensitive to regional flux deeper into the cold season but currently lack sufficient spatial coverage throughout the entire cold season. Thus, the current CO2 observing network is unlikely to detect potentially large CO2 sources associated with deep permafrost thaw and cold season respiration expected over the next 50 y. In conclusion, although continuity of current observations is vital, strategies and technologies focused on cold season measurements (active remote sensing, aircraft, and tall towers) and systematic sampling of vertical profiles across continental interiors over the full annual cycle are required to detect the onset of carbon release from thawing permafrost.},
doi = {10.1073/pnas.1601085113},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
number = 28,
volume = 113,
place = {United States},
year = {Mon Jun 27 00:00:00 EDT 2016},
month = {Mon Jun 27 00:00:00 EDT 2016}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1073/pnas.1601085113

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  • With rapid changes in climate and the seasonal amplitude of carbon dioxide (CO 2) in the Arctic, it is critical that we detect and quantify the underlying processes controlling the changing amplitude of CO 2 to better predict carbon cycle feedbacks in the Arctic climate system. We use satellite and airborne observations of atmospheric CO 2 with climatically forced CO 2 flux simulations to assess the detectability of Alaskan carbon cycle signals as future warming evolves. We find that current satellite remote sensing technologies can detect changing uptake accurately during the growing season but lack sufficient cold season coverage andmore » near-surface sensitivity to constrain annual carbon balance changes at regional scale. Airborne strategies that target regular vertical profile measurements within continental interiors are more sensitive to regional flux deeper into the cold season but currently lack sufficient spatial coverage throughout the entire cold season. Thus, the current CO 2 observing network is unlikely to detect potentially large CO 2 sources associated with deep permafrost thaw and cold season respiration expected over the next 50 y. In conclusion, although continuity of current observations is vital, strategies and technologies focused on cold season measurements (active remote sensing, aircraft, and tall towers) and systematic sampling of vertical profiles across continental interiors over the full annual cycle are required to detect the onset of carbon release from thawing permafrost.« less
  • Recent warming and drying in the arctic has resulted in a change from CO{sub 2} sink to CO{sub 2} source with respect to the atmosphere. The large stores of soil carbon of perhaps up to 177 PgC, and its sensitivity changes in soil temperature and soil moisture, mean that strong positive feedbacks on atmospheric CO{sub 2} and climate change are possible and make understanding the patterns of and controls on CO{sub 2} flux important. However, the large spatial variability in arctic tundra composition and trace gas fluxes make large-scale estimations challenging. We are using a combinations of rapid cuvette, tower-basedmore » eddy correlation, and aircraft-based eddy correlation measurements to estimate regional CO{sub 2} fluxes. Recent measurements indicate good agreement between chamber, tower-based measurements, and that most tundra sites are a source of CO{sub 2} to the atmosphere. Site specific changes in CO{sub 2} flux have been demonstrated. US IBP site 2, at Barrow, Alaska, was found to be a strong sink of CO{sub 2} of 25 g m{sup -2} y{sup -1} in the early 1970s, and is now seen to be a source of CO{sup 2} to the atmosphere of about 1.3 g C m{sup -2} y{sup -1}. A decrease in soil moisture content or water table has a greater effect on CO{sub 2} loss than does an increase in temperature. Methods of predicting fluxes from remotely sensed imagery and surface characteristics are being explored.« less
  • Given the role that forest ecosystems play in the global carbon cycle, it is important to examine what impacts a climate change scenario of altered precipitation patterns would have on such ecosystems. At Walker Branch Watershed, Oak Ridge, TN, the moisture input to a 2.5 ha upland oak-hickory forest ecosystem has been manipulated to create wet, ambient, and dry moisture regimes. CO{sub 2} efflux rates (CER) from the forest floor are being measured across all moisture regimes, using a modified LiCor 6200 closed gas exchange system. Simultaneously, soil temperature and soil water content are being monitored. Variations in soil respirationmore » measurements provide an indication of forest floor responses to changes in soil water content. With the system in place for almost 1.5 years, consistent differences in CER have not been found among the three moisture regimes. For measured dates in 1994, CER ranged from 0.70 {mu}mol m{sup -2} s{sup -1} on day 55 to 5.87 {mu}mol m{sup -2} s{sup -1} on day 168. A significant difference (P<.005) among plots was detected on day 144: the wet plot exhibited a mean CER of 21.1% higher than the lowest flux on the dry plot (2.7 versus 2.2 {mu}mol m{sup -2} s{sup -1}, respectively).« less
  • Carbon dioxide efflux and soil microenvironment were measured in three upland tundra communities in the foothills of the Brooks Range in arctic Alaska to determine the magnitude of CO{sub 2} efflux rates and the relative importance of the belowground factors that influence them. Gas exchange and soil microenvironment measurements were made weekly between 14 June and 31 July 1990. The study communities included lichen-heath, a sparse community vegetated by lichens and dwarf ericaceous shrubs on rocky soils, moist Cassiope dwarf-shrub heath tundra, dominated by Carex and evergreen and deciduous shrubs on relatively deep organic soils, and dry Cassiope dwarf-shrub heathmore » of stone-stripe areas, which was of intermediate character. Rates of CO{sub 2} efflux were similar for the three communities until mid-season when they peaked at rates between 4.9 and 5.9 g m{sup {minus}2} d{sup {minus}1}. Following the mid-season peak, the rates in all three communities declined, particularly in the lichen-heath. Seasonal patterns of CO{sub 2} efflux, soil temperature, and soil moisture suggest changing limitations to CO{sub 2} efflux, soil temperature, and soil moisture suggest changing limitations to CO{sub 2} efflux over the course of the season. Rates of carbon dioxide efflux followed changes in soil temperature early in the season when soil moisture was highest. Mid-season efflux appeared to be limited by soil, moss, and lichen hydration until the end of July, when temperature again limited efflux. Differences between the communities were related to microenvironmental differences and probable differences in carbon quality. The presence of peat-forming mosses is suggested to play an important role in differences in efflux and micro-environment among the communities. 32 refs., 3 figs., 4 tab.« less
  • A significant difference in net ecosystem carbon balance of wet sedge ecosystems in the Barrow, Alaska region was observed between CO{sub 2} flux measurements obtained during the International Biological Program in 1971 and measurements made during the 1991-1992 growing seasons. Currently, high-center polygons are net sources of CO{sub 2} to the atmosphere of {approx}14 gC{center_dot}m{sup {minus}2}{center_dot}yr{sup {minus}1}, while low-center polygons are losing {approx}3.6 gC{center_dot}m{sup {minus}2}{center_dot}yr{sup {minus}1}, and ice wedge habitats are accumulating 4.0 gC{center_dot}m{sup {minus}2}{center_dot}yr{sup {minus}1}. On average, moist meadow habitats characteristic of the IBP-II site are currently sources of {approx}1.3 gC{center_dot}m{sup {minus}2}{center_dot}yr{sup {minus}1} to the atmosphere compared to themore » reported accumulation of {approx}25 gC{center_dot}m{sup {minus}2}{center_dot}yr{sup {minus}1} determined in 1971. This difference in ecosystem function over the last two decades may be due to the recently reported increase in surface temperatures resulting in decreases in the soil moisture status. These results point to the importance of long-term research sites and databases for determining the potential effects of climate change on ecosystem function. 44 refs., 10 figs., 1 tab.« less