Differential response of carbon fluxes to climate in three peatland ecosystems that vary in the presence and stability of permafrost

Euskirchen, Eugénie; Edgar, C.; Turetsky, M. R.; Waldrop, Mark P.; Harden, Jennifer W.

doi:10.1002/2014jg002683

Cited by 111 publications

(136 citation statements)

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“…Taken together, we find that Alaskan fluxes drive a short but intense carbon uptake period, with CO 2 depletion in early summer and enrichment in late summer to early fall. These fluxes are subject to interannual variations driven by observed climate anomalies (13), which are reflected in vertical CO 2 gradients (Fig. S9), highlighting a need for year-round airborne profiles sustained over multiple consecutive years to disentangle rapid changes in uptake from slow persistent changes.…”

Section: Resultsmentioning

confidence: 99%

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Detecting regional patterns of changing CO ₂ flux in Alaska

Parazoo

Commane

Wofsy

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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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 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. 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.carbon cycle | permafrost thaw | climate | Earth system models | remote sensing T he future trajectory of carbon balance in the Arctic-Boreal Zone (ABZ) is of global importance because of the vast quantities of carbon sequestered in permafrost soils (1). Climate warming threatens to increase permafrost thaw and release soil carbon back to the atmosphere as a positive feedback promoting additional warming (2). It is unclear whether the observed intensification of the northern high-latitude carbon cycle is dominated by plant productivity or microbial decomposition, both of which seem to be increasing (3-6). Although warming temperatures and C/N fertilization promote greening and higher summer productivity during the short, intense growing season, these same factors also drive increased emissions during the long cold season (3-5).Detecting changes in ABZ carbon balance requires sustained observations over the full annual cycle. In the last decade, researchers have recognized the importance of year-round landatmosphere CO 2 flux observations (3-5). Synthesis studies of these data show that increasing growing season uptake has been offset by stronger winter respiration. Measurements of atmospheric CO 2 collected from in situ and remote sensing instruments provide spatially and temporally integrated constraints of net CO 2 exchange on regional to pan-Arctic scales. In situ observations have been limited primarily to a small network of surface towers and infrequent, short duration airborne campaigns designed primarily to detect the pan-Ar...

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Section: Resultsmentioning

confidence: 99%

“…wrote the paper. extent, and climate (13). Spatial sampling with significantly greater density than available from current ground-based and aircraft observing systems is needed.…”

mentioning

confidence: 99%

Detecting regional patterns of changing CO ₂ flux in Alaska

Parazoo

Commane

Wofsy

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…These sites include a sparsely forested thermokarst bog in central Alaska (Bonanza Creek) [Euskirchen et al, 2014], two wet sedge sites [2012][2013][2014] of mean eddy covariance NEE, EVI-based NEE, and SIF-based NEE at the (a) Bonanza Creek thermokarst bog and (b) Imnavait wet sedge sites, described in Table 1.…”

Section: Site-scale Co 2 Observationsmentioning

confidence: 99%

Tundra photosynthesis captured by satellite‐observed solar‐induced chlorophyll fluorescence

Luus¹,

Commane

Parazoo

et al. 2017

Geophysical Research Letters

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112

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Accurately quantifying the timing and magnitude of respiration and photosynthesis by high‐latitude ecosystems is important for understanding how a warming climate influences global carbon cycling. Data‐driven estimates of photosynthesis across Arctic regions often rely on satellite‐derived enhanced vegetation index (EVI); we find that satellite observations of solar‐induced chlorophyll fluorescence (SIF) provide a more direct proxy for photosynthesis. We model Alaskan tundra CO2 cycling (2012–2014) according to temperature and shortwave radiation and alternately input EVI or SIF to prescribe the annual seasonal cycle of photosynthesis. We find that EVI‐based seasonality indicates spring “green‐up” to occur 9 days prior to SIF‐based estimates, and that SIF‐based estimates agree with aircraft and tower measurements of CO2. Adopting SIF, instead of EVI, for modeling the seasonal cycle of tundra photosynthesis can result in more accurate estimates of growing season duration and net carbon uptake by arctic vegetation.

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“…The measurements and data processing are described in more detail for Imnavait in [25] and for Bonanza Creek in [26]. For all the sites, the 30-minute values were aggregated into 24-hour values (averages for T; totals for P, and ET) using MATLAB.…”

Section: Methodsmentioning

confidence: 99%

Regional Climate Model Simulation of Surface Moisture Flux Variations in Northern Terrestrial Regions

Fischer¹,

Walsh²,

Euskirchen³

et al. 2018

ACS

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The wetness of high-latitude land surfaces is strongly dependent on the difference between precipitation (P) and evapotranspiration (ET). If climate models are to capture the trajectory of surface wetness in high latitudes, they must be able to simulate the seasonality and variations of the surface moisture fluxes, as well as the sensitivities to the variations to the drivers. In this study, a combination of regional climate model output and eddy covariance measurements from flux tower locations in Alaska is used to evaluate model simulations of the surface moisture fluxes and their variations. In particular, we use the model output and the field measurements to test the hypothesis that temperature (T) is the key driver of variations of ET in tundra regions underlain by permafrost, while precipitation plays a greater role in boreal forest areas. Although the model's hydrologic cycle is stronger (larger P, larger ET) relative to the in situ measurements at all the sites, the prominent seasonal cycles of P, T, and ET are captured by the model. The tower measurements from all sites show a short period (one or two months) of negative P-ET during summer, indicative of surface drying, although the model does not show this period of drying at the inland tundra site. At all the tundra sites, both the flux tower data and the model simulations show that daily and warm-season totals of ET are largely temperature-driven. Daily ET shows a weak negative correlation with precipitation in the measurements and in the model results for all the sites. Precipitation is the main driver of year-to-year variations of the seasonally integrated net moisture flux at all the sites, implying that precipitation will be at least as important as temperature in the future trajectory of surface wetness.

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Differential response of carbon fluxes to climate in three peatland ecosystems that vary in the presence and stability of permafrost

Cited by 111 publications

References 90 publications

Detecting regional patterns of changing CO ₂ flux in Alaska

Detecting regional patterns of changing CO ₂ flux in Alaska

Tundra photosynthesis captured by satellite‐observed solar‐induced chlorophyll fluorescence

Regional Climate Model Simulation of Surface Moisture Flux Variations in Northern Terrestrial Regions

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Differential response of carbon fluxes to climate in three peatland ecosystems that vary in the presence and stability of permafrost

Cited by 111 publications

References 90 publications

Detecting regional patterns of changing CO 2 flux in Alaska

Detecting regional patterns of changing CO 2 flux in Alaska

Tundra photosynthesis captured by satellite‐observed solar‐induced chlorophyll fluorescence

Regional Climate Model Simulation of Surface Moisture Flux Variations in Northern Terrestrial Regions

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Detecting regional patterns of changing CO ₂ flux in Alaska

Detecting regional patterns of changing CO ₂ flux in Alaska