scholarly journals Vegetation greenness and land carbon-flux anomalies associated with climate variations: a focus on the year 2015

2017 ◽  
Vol 17 (22) ◽  
pp. 13903-13919 ◽  
Author(s):  
Chao Yue ◽  
Philippe Ciais ◽  
Ana Bastos ◽  
Frederic Chevallier ◽  
Yi Yin ◽  
...  
Keyword(s):  
Carbon Source ◽  
El Niño ◽  
El Nino ◽  
Carbon Sink ◽  
Growing Season ◽  
Satellite Observations ◽  
Carbon Uptake ◽  
Climate Variations ◽  
Strong Transition ◽  
The Tropics

Abstract. Understanding the variations in global land carbon uptake, and their driving mechanisms, is essential if we are to predict future carbon-cycle feedbacks on global environmental changes. Satellite observations of vegetation greenness have shown consistent greening across the globe over the past three decades. Such greening has driven the increasing land carbon sink, especially over the growing season in northern latitudes. On the other hand, interannual variations in land carbon uptake are strongly influenced by El Niño–Southern Oscillation (ENSO) climate variations. Marked reductions in land uptake and strong positive anomalies in the atmospheric CO2 growth rates occur during El Niño events. Here we use the year 2015 as a natural experiment to examine the possible response of land ecosystems to a combination of vegetation greening and an El Niño event. The year 2015 was the greenest year since 2000 according to satellite observations, but a record atmospheric CO2 growth rate also occurred due to a weaker than usual land carbon sink. Two atmospheric inversions indicate that the year 2015 had a higher than usual northern land carbon uptake in boreal spring and summer, consistent with the positive greening anomaly and strong warming. This strong uptake was, however, followed by a larger source of CO2 in the autumn. For the year 2015, enhanced autumn carbon release clearly offset the extra uptake associated with greening during the summer. This finding leads us to speculate that a long-term greening trend may foster more uptakes during the growing season, but no large increase in annual carbon sequestration. For the tropics and Southern Hemisphere, a strong transition towards a large carbon source for the last 3 months of 2015 is discovered, concomitant with El Niño development. This transition of terrestrial tropical CO2 fluxes between two consecutive seasons is the largest ever found in the inversion records. The strong transition to a carbon source in the tropics with the peak of El Niño is consistent with historical observations, but the detailed mechanisms underlying such an extreme transition remain to be elucidated.

scholarly journals Abrupt seasonal transitions in land carbon uptake in 2015

2017 ◽  
Author(s):  
Chao Yue ◽  
Philippe Ciais ◽  
Ana Bastos ◽  
Frederic Chevallier ◽  
Yi Yin ◽  
...  
Keyword(s):  
Growth Rate ◽  
Carbon Source ◽  
Southern Hemisphere ◽  
Carbon Sink ◽  
Growing Season ◽  
Satellite Observations ◽  
Carbon Uptake ◽  
Co2 Fluxes ◽  
Abrupt Transition ◽  
The Tropics

Abstract. The year 2015 saw a record atmospheric CO2 growth rate associated with a weaker than usual land carbon sink. Paradoxically, it was also the greenest year since 2000 according to satellite observations of vegetation greenness. To reconcile these two seemingly paradoxical observations, we examined the patterns of CO2 fluxes using two atmospheric inversions. Inversion results indicate that the year 2015 had a higher than usual northern land carbon uptake in spring and summer, consistent with the greening anomaly. This higher uptake was however followed by a larger source of CO2 in autumn, suggesting a coupling between growing season uptake and late season release of CO2. For the tropics and Southern Hemisphere, a strong and abrupt transition toward a large carbon source for the last trimester of 2015 is discovered, concomitant with the El Niño development. This abrupt transition of terrestrial tropical CO2 fluxes between two consecutive seasons is the largest ever found in the inversion records.

scholarly journals Impact of the 2015/2016 El Niño on the terrestrial carbon cycle constrained by bottom-up and top-down approaches

2018 ◽  
Vol 373 (1760) ◽  
pp. 20170304 ◽  
Author(s):  
Ana Bastos ◽  
Pierre Friedlingstein ◽  
Stephen Sitch ◽  
Chi Chen ◽  
Arnaud Mialon ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
El Niño ◽  
El Nino ◽  
Carbon Sink ◽  
Terrestrial Carbon ◽  
Fire Emissions ◽  
Terrestrial Carbon Cycle ◽  
Depth Analysis ◽  
The Tropics ◽  
The Impact

Evaluating the response of the land carbon sink to the anomalies in temperature and drought imposed by El Niño events provides insights into the present-day carbon cycle and its climate-driven variability. It is also a necessary step to build confidence in terrestrial ecosystems models' response to the warming and drying stresses expected in the future over many continents, and particularly in the tropics. Here we present an in-depth analysis of the response of the terrestrial carbon cycle to the 2015/2016 El Niño that imposed extreme warming and dry conditions in the tropics and other sensitive regions. First, we provide a synthesis of the spatio-temporal evolution of anomalies in net land–atmosphere CO 2 fluxes estimated by two in situ measurements based on atmospheric inversions and 16 land-surface models (LSMs) from TRENDYv6. Simulated changes in ecosystem productivity, decomposition rates and fire emissions are also investigated. Inversions and LSMs generally agree on the decrease and subsequent recovery of the land sink in response to the onset, peak and demise of El Niño conditions and point to the decreased strength of the land carbon sink: by 0.4–0.7 PgC yr −1 (inversions) and by 1.0 PgC yr −1 (LSMs) during 2015/2016. LSM simulations indicate that a decrease in productivity, rather than increase in respiration, dominated the net biome productivity anomalies in response to ENSO throughout the tropics, mainly associated with prolonged drought conditions. This article is part of a discussion meeting issue ‘The impact of the 2015/2016 El Niño on the terrestrial tropical carbon cycle: patterns, mechanisms and implications’.

scholarly journals The Response of Tropical Atmospheric Energy Budgets to ENSO*

2013 ◽  
Vol 26 (13) ◽  
pp. 4710-4724 ◽  
Author(s):  
Michael Mayer ◽  
Kevin E. Trenberth ◽  
Leopold Haimberger ◽  
John T. Fasullo
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Warm Pool ◽  
Smooth Transition ◽  
Energy Budgets ◽  
Enso Events ◽  
El Niño Modoki ◽  
Static Energy ◽  
The Tropics

Abstract The variability of zonally resolved tropical energy budgets in association with El Niño–Southern Oscillation (ENSO) is investigated. The most recent global atmospheric reanalyses from 1979 to 2011 are employed with removal of apparent discontinuities to obtain best possible temporal homogeneity. The growing length of record allows a more robust analysis of characteristic patterns of variability with cross-correlation, composite, and EOF methods. A quadrupole anomaly pattern is found in the vertically integrated energy divergence associated with ENSO, with centers over the Indian Ocean, the Indo-Pacific warm pool, the eastern equatorial Pacific, and the Atlantic. The smooth transition, particularly of the main maxima of latent and dry static energy divergence, from the western to the eastern Pacific is found to require at least two EOFs to be adequately described. The canonical El Niño pattern (EOF-1) and a transition pattern (EOF-2; referred to as El Niño Modoki by some authors) form remarkably coherent ENSO-related anomaly structures of the tropical energy budget not only over the Pacific but throughout the tropics. As latent and dry static energy divergences show strong mutual cancellation, variability of total energy divergence is smaller and more tightly coupled to local sea surface temperature (SST) anomalies and is mainly related to the ocean heat discharge and recharge during ENSO peak phases. The complexity of the structures throughout the tropics and their evolution during ENSO events along with their interactions with the annual cycle have often not been adequately accounted for; in particular, the El Niño Modoki mode is but part of the overall evolutionary patterns.

scholarly journals Different climate sensitivity for radial growth, but uniform for tree-ring stable isotopes along an aridity gradient in Polylepis tarapacana, the world’s highest elevation tree-species

2021 ◽  
Author(s):  
Milagros Rodriguez-Caton ◽  
Laia Andreu-Hayles ◽  
Mariano S Morales ◽  
Valérie Daux ◽  
Duncan A Christie ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Carbon Source ◽  
Tree Ring ◽  
Tree Growth ◽  
Carbon Sink ◽  
Growing Season ◽  
Wood Formation ◽  
Aridity Gradient ◽  
Leaf Level ◽  
Δ13c And Δ18o

Abstract Tree growth is generally considered to be temperature-limited at upper elevation treelines. Yet, climate factors controlling tree growth at semiarid treelines are poorly understood. We explored the influence of climate on stem growth and stable isotopes for Polyepis tarapacana, the world’s highest elevation tree-species found only in the South American Altiplano. We developed tree-ring width index (RWI), oxygen (δ18O) and carbon (δ13C) chronologies for the last 60 years at four P. tarapacana stands located above 4,400 meters in elevation, along a 500-km latitude-aridity gradient. Total annual precipitation decreased from 300 to 200 mm from the northern to the southern sites. We used RWI as a proxy of wood formation (carbon sink) and isotopic tree-ring signatures as proxies of leaf-level gas exchange processes (carbon source). We found distinct climatic conditions regulating carbon-sink processes along the gradient. Current-growing season temperature regulated RWI at wetter-northern sites, while prior-growing season precipitation determined RWI at arid-southern sites. This suggests that the relative importance of temperature to precipitation in regulating tree growth is driven by site-water availability. In contrast, warm and dry growing-seasons resulted in enriched tree-ring δ13C and δ18O at all study sites, suggesting that similar climate conditions control carbon-source processes. Site-level δ13C and δ18O chronologies were significantly and positively related at all sites, with the strongest relationships among the southern-drier stands. This indicates an overall regulation of intercellular carbon dioxide via stomatal conductance for the entire P. tarapacana network, with greater stomatal control when aridity increases. The manuscript also highlights a coupling and decoupling of physiological processes at leaf level versus wood formation depending on their respectively uniform and distinct sensitivity to climate. This study contributes to better understand and predict the response of high-elevation Polylepis woodlands to rapid climate changes and projected drying in the Altiplano.

scholarly journals A successful prediction of the record CO 2 rise associated with the 2015/2016 El Niño

2018 ◽  
Vol 373 (1760) ◽  
pp. 20170301 ◽  
Author(s):  
Richard A. Betts ◽  
Chris D. Jones ◽  
Jeff. R. Knight ◽  
Ralph. F. Keeling ◽  
John. J. Kennedy ◽  
...  
Keyword(s):  
El Niño ◽  
El Nino ◽  
Carbon Sink ◽  
Carbon Dioxide Concentration ◽  
Anthropogenic Emissions ◽  
First Year ◽  
Mauna Loa ◽  
Simple Extrapolation ◽  
Biosphere Model ◽  
The Impact

In early 2016, we predicted that the annual rise in carbon dioxide concentration at Mauna Loa would be the largest on record. Our forecast used a statistical relationship between observed and forecast sea surface temperatures in the Niño 3.4 region and the annual CO 2 rise. Here, we provide a formal verification of that forecast. The observed rise of 3.4 ppm relative to 2015 was within the forecast range of 3.15 ± 0.53 ppm, so the prediction was successful. A global terrestrial biosphere model supports the expectation that the El Niño weakened the tropical land carbon sink. We estimate that the El Niño contributed approximately 25% to the record rise in CO 2 , with 75% due to anthropogenic emissions. The 2015/2016 CO 2 rise was greater than that following the previous large El Niño in 1997/1998, because anthropogenic emissions had increased. We had also correctly predicted that 2016 would be the first year with monthly mean CO 2 above 400 ppm all year round. We now estimate that atmospheric CO 2 at Mauna Loa would have remained above 400 ppm all year round in 2016 even if the El Niño had not occurred, contrary to our previous expectations based on a simple extrapolation of previous trends. This article is part of a discussion meeting issue ‘The impact of the 2015/2016 El Niño on the terrestrial tropical carbon cycle: patterns, mechanisms and implications’.

scholarly journals Structural changes in the shallow and transition branch of the Brewer–Dobson circulation induced by El Niño

2018 ◽  
Author(s):  
Mohamadou Diallo ◽  
Paul Konopka ◽  
Michelle L. Santee ◽  
Rolf Müller ◽  
Mengchu Tao ◽  
...  
Keyword(s):  
El Niño ◽  
Structural Changes ◽  
Lower Stratosphere ◽  
Transport Model ◽  
El Nino ◽  
Southern Oscillation ◽  
Satellite Observations ◽  
Trace Gas ◽  
Residual Circulation ◽  
Mixing Ratios

Abstract. The stratospheric Brewer–Dobson circulation (BD-circulation) determines the transport and lifetime of key radiatively active trace gases and further impacts surface climate through downward coupling. Here, we quantify the variability in the lower stratospheric BD-circulation induced by the El Nino Southern Oscillation (ENSO), using satellite trace gas measurements and simulations with the Lagrangian chemistry transport model, CLaMS, driven by ERA-Interim and JRA-55 reanalyses. We show that despite discrepancies in the deseasonalised ozone (O3) mixing ratios between CLaMS simulations and satellite observations, the patterns of changes in the lower stratospheric O3 anomalies induced by ENSO agree remarkably well over the 2005–2016 period. Particularly during the most recent El Niño in 2015–2016, both satellite observations and CLaMS simulations show the largest negative tropical O3 anomaly in the record. Regression analysis of different metrics of the BD-circulation strength, including mean age of air, vertical velocity, residual circulation and age spectrum, shows clear evidence for structural changes of the BD-circulation in the lower stratosphere induced by El Niño, consistent with observed O3 anomalies. These structural changes during El Niño include a weakening of the transition branch of the BD-circulation between about 370–420 K (∼ 100–70 hPa) and equatorward of about 60° and, a strengthening of the shallow branch at the same latitudes and between about 420–500 K (∼ 70–30 hPa). The strengthening of the shallow branch induces negative tropical O3 anomalies due to enhanced tropical upwelling, while the weakening of the transition branch combined with enhanced downwelling due to the strengthening shallow branch leads to positive O3 anomalies in the extratropical upper troposphere-lower stratosphere (UTLS). Our results suggest that a shift of the ENSO basic state toward more frequent El Niño-like conditions in a warming future climate will substantially alter UTLS trace gas distributions due to these changes in the vertical structure of the stratospheric circulation.

scholarly journals The role of satellite observations in understanding the impact of El Niño on the carbon cycle: current capabilities and future opportunities

2018 ◽  
Vol 373 (1760) ◽  
pp. 20170407 ◽  
Author(s):  
Paul I. Palmer
Keyword(s):  
Carbon Cycle ◽  
Satellite Data ◽  
El Niño ◽  
El Nino ◽  
Carbon Dynamics ◽  
Climate Variation ◽  
Satellite Observations ◽  
Future Research ◽  
The Impact

The 2015/2016 El Niño was the first major climate variation when there were a range of satellite observations that simultaneously observed land, ocean and atmospheric properties associated with the carbon cycle. These data are beginning to provide new insights into the varied responses of land ecosystems to El Niño, but we are far from fully exploiting the information embodied by these data. Here, we briefly review the atmospheric and terrestrial satellite data that are available to study the carbon cycle. We also outline recommendations for future research, particularly the closer integration of satellite data with forest biometric datasets that provide detailed information about carbon dynamics on a range of timescales. This article is part of a discussion meeting issue ‘The impact of the 2015/2016 El Niño on the terrestrial tropical carbon cycle: patterns, mechanisms and implications’.

scholarly journals The impact of the 2015/2016 El Niño on global photosynthesis using satellite remote sensing

2018 ◽  
Vol 373 (1760) ◽  
pp. 20170409 ◽  
Author(s):  
Xiangzhong Luo ◽  
Trevor F. Keenan ◽  
Joshua B. Fisher ◽  
Juan-Carlos Jiménez-Muñoz ◽  
Jing M. Chen ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Carbon Cycle ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Carbon Sink ◽  
Global Climate ◽  
Prognostic Models ◽  
Positive Anomaly ◽  
The Impact

The El Niño-Southern Oscillation exerts a large influence on global climate regimes and on the global carbon cycle. Although El Niño is known to be associated with a reduction of the global total land carbon sink, results based on prognostic models or measurements disagree over the relative contribution of photosynthesis to the reduced sink. Here, we provide an independent remote sensing-based analysis on the impact of the 2015–2016 El Niño on global photosynthesis using six global satellite-based photosynthesis products and a global solar-induced fluorescence (SIF) dataset. An ensemble of satellite-based photosynthesis products showed a negative anomaly of −0.7 ± 1.2 PgC in 2015, but a slight positive anomaly of 0.05 ± 0.89 PgC in 2016, which when combined with observations of the growth rate of atmospheric carbon dioxide concentrations suggests that the reduction of the land residual sink was likely dominated by photosynthesis in 2015 but by respiration in 2016. The six satellite-based products unanimously identified a major photosynthesis reduction of −1.1 ± 0.52 PgC from savannahs in 2015 and 2016, followed by a highly uncertain reduction of −0.22 ± 0.98 PgC from rainforests. Vegetation in the Northern Hemisphere enhanced photosynthesis before and after the peak El Niño, especially in grasslands (0.33 ± 0.13 PgC). The patterns of satellite-based photosynthesis ensemble mean were corroborated by SIF, except in rainforests and South America, where the anomalies of satellite-based photosynthesis products also diverged the most. We found the inter-model variation of photosynthesis estimates was strongly related to the discrepancy between moisture forcings for models. These results highlight the importance of considering multiple photosynthesis proxies when assessing responses to climatic anomalies. This article is part of a discussion meeting issue ‘The impact of the 2015/2016 El Niño on the terrestrial tropical carbon cycle: patterns, mechanisms and implications'.

scholarly journals Meridional Extent and Interannual Variability of the Pacific Ocean Tropical–Subtropical Warm Water Exchange

2005 ◽  
Vol 35 (3) ◽  
pp. 323-335 ◽  
Author(s):  
Christopher S. Meinen
Keyword(s):  
Pacific Ocean ◽  
El Niño ◽  
El Nino ◽  
Warm Water ◽  
Height Anomaly ◽  
The South ◽  
El Niño Event ◽  
The Pacific ◽  
The Pacific Ocean ◽  
The Tropics

Abstract Altimetric observations of sea surface height anomaly (SSHA) from the TOPEX/Poseidon and ERS satellites, hydrography, and the ECMWF and Florida State University wind products are used to track warm water (≥20°C) as it is exchanged between the equatorial Pacific Ocean and the higher latitudes during 1993–2003. The large El Niño event of 1997–98 resulted in a significant discharge of warm water toward the higher latitudes within the interior of the Pacific Ocean. The exchange of anomalous warm water volume with the Northern Hemisphere appears to be blocked under the intertropical convergence zone, consistent with most current ideas on the time-mean tropical–subtropical exchange. Little of the warm water discharged northward across 5° and 8°N during the 1997–98 El Niño event could be traced as far as 10°N. To the south, however, these anomalous volumes of warm water were visible at least as far as 20°S, primarily in the longitudes around 130°–160°W. In both hemispheres most of the warm water appeared to flow westward before returning to the Tropics during the recharge phase of the El Niño–La Niña cycle. The buildup of warm water in the Tropics before the 1997–98 El Niño is shown to be fed primarily by warm water drawn from the region in the western Pacific within 5°S–15°N. The exchange cycle between the equatorial band and the higher latitudes north of the equator leads the cycle in the south by 6–8 months. These results are found in all three datasets used herein, hydrography, altimetric observations of SSHA, and Sverdrup transports calculated from multiple wind products, which demonstrates the robustness of the results.

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