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  • Carbon cycle  (6)
  • Hydrothermal  (6)
  • American Geophysical Union  (12)
  • 2010-2014  (12)
  • 1995-1999
  • 2010  (12)
  • 1999
  • 1
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    Nitrogen attenuation of terrestrial carbon cycle response to global environmental factors (2010)
    American Geophysical Union
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Geophysical Union, 2009. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 23 (2009): GB4028, doi:10.1029/2009GB003519.
    Beschreibung: Nitrogen cycle dynamics have the capacity to attenuate the magnitude of global terrestrial carbon sinks and sources driven by CO2 fertilization and changes in climate. In this study, two versions of the terrestrial carbon and nitrogen cycle components of the Integrated Science Assessment Model (ISAM) are used to evaluate how variation in nitrogen availability influences terrestrial carbon sinks and sources in response to changes over the 20th century in global environmental factors including atmospheric CO2 concentration, nitrogen inputs, temperature, precipitation and land use. The two versions of ISAM vary in their treatment of nitrogen availability: ISAM-NC has a terrestrial carbon cycle model coupled to a fully dynamic nitrogen cycle while ISAM-C has an identical carbon cycle model but nitrogen availability is always in sufficient supply. Overall, the two versions of the model estimate approximately the same amount of global mean carbon uptake over the 20th century. However, comparisons of results of ISAM-NC relative to ISAM-C reveal that nitrogen dynamics: (1) reduced the 1990s carbon sink associated with increasing atmospheric CO2 by 0.53 PgC yr−1 (1 Pg = 1015g), (2) reduced the 1990s carbon source associated with changes in temperature and precipitation of 0.34 PgC yr−1 in the 1990s, (3) an enhanced sink associated with nitrogen inputs by 0.26 PgC yr−1, and (4) enhanced the 1990s carbon source associated with changes in land use by 0.08 PgC yr−1 in the 1990s. These effects of nitrogen limitation influenced the spatial distribution of the estimated exchange of CO2 with greater sink activity in high latitudes associated with climate effects and a smaller sink of CO2 in the southeastern United States caused by N limitation associated with both CO2 fertilization and forest regrowth. These results indicate that the dynamics of nitrogen availability are important to consider in assessing the spatial distribution and temporal dynamics of terrestrial carbon sources and sinks.
    Beschreibung: We also acknowledge the financial support of the National Aeronautics and Space Administration Land Cover and Land Use Change Program (NNX08AK75G).
    Schlagwort(e): Nitrogen cycle ; Carbon cycle ; ISAM
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  • 2
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    Microearthquake patterns following the 1998 eruption of Axial Volcano, Juan de Fuca Ridge : mechanical relaxation and thermal strain (2010)
    American Geophysical Union
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 109 (2004): B01101, doi:10.1029/2003JB002499.
    Beschreibung: Ocean bottom seismic networks deployed following the 1998 eruption of Axial seamount reveal an evolving pattern of microearthquake activity associated with subsurface magmatism and thermal strain. Seismicity rates decay steadily over 15 months of observation (February 8, 1998, to April 30, 1999), consistent with a trend toward thermal and mechanical equilibrium in the shallow crust after the magmatic event. Immediately after the eruption, seismicity rates were high for about 60 days in the southeast corner of the caldera where lava flows from the 1998 eruption were mapped. A small burst of seismic activity was observed on the southeast shoulder of the volcano from 100 to 150 days after the eruption. These events, which are characterized by slip on nearly vertical faults in the shallow crust, extend about 6 km from the southeast corner of the caldera and overlie a mid-crustal low-velocity zone. After this episode, seismicity rates remain low until the end of the observation period, 455 days after the eruption. Shallow (~0.7 km depth) events, consistent with thermal contraction and volume changes of ~2 × 10−3 m3 in ~5 m3 sources, are observed in individual clusters beneath hydrothermal vents within the 1998 lava flow at the southeast edge of the caldera. Microearthquakes observed during the last 70 days of observation are distributed around the central caldera, most likely representing small amounts of subsidence on caldera faults during the final stages of equilibration following melt withdrawal associated with the 1998 eruption.
    Beschreibung: Sohn, Webb, and the field program were supported by NSF grant OCE 97- 11700. Barclay was supported in part by the Woods Hole Oceanographic Institution.
    Schlagwort(e): Microearthquakes ; Hydrothermal ; Magmatism
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  • 3
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    Hydrothermal activity on the ultra-slow spreading southern Knipovich Ridge (2010)
    American Geophysical Union
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 8 (2007): Q08013, doi:10.1029/2007GC001652.
    Beschreibung: We report first evidence for hydrothermal activity from the southern Knipovich Ridge, an ultra-slow spreading ridge segment in the Norwegian-Greenland Sea. Evidence comes from optical backscatter anomalies collected during a systematic side-scan sonar survey of the ridge axis, augmented by the identification of biogeochemical tracers in the overlying water column that are diagnostic of hydrothermal plume discharge (Mn, CH4, ATP). Analysis of coregistered geologic and oceanographic data reveals that the signals we have identified are consistent with a single high-temperature hydrothermal source, located distant from any of the axial volcanic centers that define second-order segmentation along this oblique ridge system. Rather, our data indicate a hydrothermal source associated with highly tectonized seafloor that may be indicative of serpentinizing ultramafic outcrops. Consistent with this hypothesis, the hydrothermal plume signals we have detected exhibit a high methane to manganese ratio of 2–3:1. This is higher than that typical of volcanically hosted vent sites and provides further evidence that the source of the plume signals reported here is most probably a high-temperature hydrothermal field that experiences some ultramafic influence (compare to Rainbow and Logachev sites, Mid-Atlantic Ridge). While such sites have previously been invoked to be common on the SW Indian Ridge, this may be the first such site to be located along the Arctic ultra-slow spreading ridge system.
    Beschreibung: Connelly and German were funded by NERC grant NER/B/S/ 2000/00755, NERC Core Strategic Funding at NOC, and the ChEss project of the Census of Marine Life.
    Schlagwort(e): Hydrothermal ; Arctic ; Serpentinization ; Knipovich Ridge
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  • 4
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    Mineral phase analysis of deep-sea hydrothermal particulates by a Raman spectroscopy expert algorithm : toward autonomous in situ experimentation and exploration (2010)
    American Geophysical Union
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Geophysical Union, 2009. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 10 (2009): Q05T05, doi:10.1029/2008GC002314.
    Beschreibung: This paper demonstrates that a Raman spectroscopy, point-counting technique can be used for phase analysis of minerals commonly found in deep-sea hydrothermal plumes, even for minerals with similar chemical compositions. It also presents our robust autonomous identification algorithm and spectral database, both of which were developed specifically for deep-sea hydrothermal studies. The Raman spectroscopy expert algorithm was developed and tested against multicomponent mixtures of minerals relevant to the deep-sea hydrothermal environment. It is intended for autonomous classification where many spectra must be examined with little or no human involvement to increase analytic precision, accuracy, and data volume or to enable in situ measurements and experimentation.
    Beschreibung: Support for J.A.B. was provided through a RIDGE 2000 Postdoctoral Fellowship (NSF OCE-0550331).
    Schlagwort(e): Hydrothermal ; Mineralogy ; Optical instruments ; Raman spectroscopy ; Analytic techniques ; Chemical sensor
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  • 5
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    Enhanced CO2 outgassing in the Southern Ocean from a positive phase of the Southern Annular Mode (2010)
    American Geophysical Union
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 21 (2007): GB2026, doi:10.1029/2006GB002900.
    Beschreibung: We investigate the interannual variability in the flux of CO2 between the atmosphere and the Southern Ocean on the basis of hindcast simulations with a coupled physical-biogeochemical-ecological model with particular emphasis on the role of the Southern Annular Mode (SAM). The simulations are run under either pre-industrial or historical CO2 concentrations, permitting us to separately investigate natural, anthropogenic, and contemporary CO2 flux variability. We find large interannual variability (±0.19 PgC yr−1) in the contemporary air-sea CO2 flux from the Southern Ocean (〈35°S). Forty-three percent of the contemporary air-sea CO2 flux variance is coherent with SAM, mostly driven by variations in the flux of natural CO2, for which SAM explains 48%. Positive phases of the SAM are associated with anomalous outgassing of natural CO2 at a rate of 0.1 PgC yr−1 per standard deviation of the SAM. In contrast, we find an anomalous uptake of anthropogenic CO2 at a rate of 0.01 PgC yr−1 during positive phases of the SAM. This uptake of anthropogenic CO2 only slightly mitigates the outgassing of natural CO2, so that a positive SAM is associated with anomalous outgassing in contemporaneous times. The primary cause of the natural CO2 outgassing is anomalously high oceanic partial pressures of CO2 caused by elevated dissolved inorganic carbon (DIC) concentrations. These anomalies in DIC are primarily a result of the circulation changes associated with the southward shift and strengthening of the zonal winds during positive phases of the SAM. The secular, positive trend in the SAM has led to a reduction in the rate of increase of the uptake of CO2 by the Southern Ocean over the past 50 years.
    Beschreibung: This work was supported by NASA headquarters under the Earth System Science Fellowship Grant NNG05GP78H to N. S. L. and grants NAG5-12528 and NNG04GH53G to N. G. Both S. C. D. and I. D. L. were supported by NSF/ONR NOPP (N000140210370) and NASA (NNG05GG30G).
    Schlagwort(e): Southern Ocean ; Carbon cycle ; Southern Annular Mode
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  • 6
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    Hydrothermal circulation within the Endeavour Segment, Juan de Fuca Ridge (2010)
    American Geophysical Union
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Geophysical Union, 2010. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 11 (2010): Q05002, doi:10.1029/2009GC002957.
    Beschreibung: Areas of the seafloor at mid-ocean ridges where hydrothermal vents discharge are easily recognized by the dramatic biological, physical, and chemical processes that characterize such sites. Locations where seawater flows into the seafloor to recharge hydrothermal cells within the crustal reservoir are by contrast almost invisible but can be indirectly identified by a systematic grid of conductive heat flow measurements. An array of conductive heat flow stations in the Endeavour axial valley of the Juan de Fuca Ridge has identified recharge zones that appear to represent a nested system of fluid circulation paths. At the scale of an axial rift valley, conductive heat flow data indicate a general cross-valley fluid flow, where seawater enters the shallow subsurface crustal reservoir at the eastern wall of the Endeavour axial valley and undergoes a kilometer of horizontal transit beneath the valley floor, finally exiting as warm hydrothermal fluid discharge on the western valley bounding wall. Recharge zones also have been identified as located within an annular ring of very cold seafloor around the large Main Endeavour Hydrothermal Field, with seawater inflow occurring within faults that surround the fluid discharge sites. These conductive heat flow data are consistent with previous models where high-temperature fluid circulation cells beneath large hydrothermal vent fields may be composed of narrow vertical cylinders. Subsurface fluid circulation on the Endeavour Segment occurs at various crustal depths in three distinct modes: (1) general east to west flow across the entire valley floor, (2) in narrow cylinders that penetrate deeply to high-temperature heat sources, and (3) supplying low-temperature diffuse vents where seawater is entrained into the shallow uppermost crust by the adjacent high-temperature cylindrical systems. The systematic array of conductive heat flow measurements over the axial valley floor averaged ∼150 mW/m2, suggesting that only about 3% of the total energy flux of ocean crustal formation is removed by conductive heat transfer, with the remainder being dissipated to overlying seawater by fluid advection.
    Beschreibung: Funding was provided by NSF grants OCE0318566 and OCE0241294 and NSF/SGER grant OCE0902626.
    Schlagwort(e): Hydrothermal ; Juan de Fuca ; Vents
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  • 7
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    Constraining ventilation during deepwater formation using deep ocean measurements of the dissolved gas ratios 40Ar/36Ar, N2/Ar, and Kr/Ar (2010)
    American Geophysical Union
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Geophysical Union, 2010. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 115 (2010): C11015, doi:10.1029/2010JC006152.
    Beschreibung: The concentration of inert gases and their isotopes in the deep ocean are useful as tracers of air-sea gas exchange during deepwater formation. ΔKr/Ar, ΔN2/Ar, and δ40Ar were measured in deep profiles of samples collected in the northwest Pacific, subtropical North Pacific and tropical Atlantic oceans. For the ocean below 2000 m, we determined a mean ΔKr/Ar composition of −0.96% ± 0.16%, a mean ΔN2/Ar of 1.29% ± 0.21% relative to equilibrium saturation, and for δ40Ar a value of 1.188‰ ± 0.055‰ relative to air. These data are used to constrain high-latitude ventilation processes in the framework of three-box and seven-box ocean models. For the three-box model tracer data, we constrain the appropriate surface area of the high-latitude region in both models to be 3.6% (+2.5%, −1.7%) of ocean surface area and the bubble air injection rate to be 22.7 (+8.8, −7.3) mol air m−2 yr−1. Results for the seven-box model were similar, with a high-latitude area of 3.3% (+2.2%, −1.3%). Our results provide geochemical support for suggestions that the effective area of high-latitude ventilation is much smaller than the region of elevated preformed nutrients and demonstrate that noble gases strongly constrain the ocean solubility pump. Reducing high-latitude surface area weakens the CO2 solubility pump in the box models and limits communication between the atmosphere and deep ocean. These tracers should be useful constraints on high-latitude ventilation and the strength of the solubility pump in more complex ocean general circulation models.
    Beschreibung: Funding was provided by NSF‐OCE‐0647979.
    Schlagwort(e): Noble gases ; Ventilation ; Carbon cycle ; Solubility pump ; Gas exchange
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  • 8
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    Methane, manganese, and helium in hydrothermal plumes following volcanic eruptions on the East Pacific Rise near 9°50′N (2010)
    American Geophysical Union
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 9 (2008): Q06T01, doi:10.1029/2008GC002104.
    Beschreibung: As part of a rapid response cruise in May 2006, we surveyed water column hydrothermal plumes and bottom conditions on the East Pacific Rise between 9°46.0′N and 9°57.6′N, where recent seafloor volcanic activity was suspected. Real-time measurements included temperature, light transmission, and salinity. Samples of the plume waters were analyzed for methane, manganese, helium concentrations, and the δ 13C of methane. These data allow us to examine the effects of the 2005–2006 volcanic eruption(s) on plume chemistry. Methane and manganese are sensitive tracers of hydrothermal plumes, and both were present in high concentrations. Methane reached 347 nM in upper plume samples (250 m above seafloor) and exceeded 1085 nM in a near-bottom sample. Mn reached 54 nM in the upper plume and 98 nM in near-bottom samples. The concentrations of methane and Mn were higher than measurements made after a volcanic eruption in the same area in 1991, but the ratio of CH4/Mn, at 6.7, is slightly lower, though still well above the ratios measured in chronic plumes. High concentrations of methane in near-bottom samples were associated with areas of microbial mats and diffuse venting documented in seafloor imagery. The isotopic composition of the methane carbon shows evidence of active microbial oxidation; however, neither the fractionation factor nor the source of the eruption-associated methane can be determined with any certainty. Considerable scatter in the isotopic data is due to diverse sources for the methane as well as fractionation as methane is consumed. One sample at +21‰ versus Peedee belemnite standard is among the most enriched methane carbon values reported in a hydrothermal plume to date.
    Beschreibung: This field work was supported by NSF awards OCE0222069 (J.P.C., M.D.L.); OCE0525863 (D.J.F.); and OCE0327261 (T.M..S.); and the NASA Astrobiology Institute (JPC). The NOAA-VENTS program provided additional support through a grant to the Joint Institute for the Study of the Atmosphere and Ocean (JISAO) under NOAA Cooperative Agreement NA17RJ1232.
    Schlagwort(e): Hydrothermal ; Plume ; Methane isotopes
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  • 9
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    Bottom pressure signals at the TAG deep-sea hydrothermal field : evidence for short-period, flow-induced ground deformation (2010)
    American Geophysical Union
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    Publikationsdatum: 2022-05-26
    Beschreibung: Author Posting. © American Geophysical Union, 2009. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 36 (2009): L19301, doi:10.1029/2009GL040006.
    Beschreibung: Bottom pressure measurements acquired from the TAG hydrothermal field on the Mid-Atlantic Ridge (26°N) contain clusters of narrowband spectral peaks centered at periods from 22 to 53.2 minutes. The strongest signal at 53.2 min corresponds to 13 mm of water depth variation. Smaller, but statistically significant, signals were also observed at periods of 22, 26.5, 33.4, and 37.7 min (1–4 mm amplitude). These kinds of signals have not previously been observed in the ocean, and they appear to represent vertical motion of the seafloor in response to hydrothermal flow - similar in many ways to periodic terrestrial geysers. We demonstrate that displacements of 13 mm can be produced by relatively small flow-induced pressures (several kPa) if the source region is less than ∼100 m below the seafloor. We suggest that the periodic nature of the signals results from a non-linear relationship between fluid pore pressure and crustal permeability.
    Schlagwort(e): Ground ; Displacement ; Hydrothermal
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  • 10
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    How does ocean biology affect atmospheric pCO2? Theory and models (2010)
    American Geophysical Union
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    Publikationsdatum: 2022-05-26
    Beschreibung: Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 113 (2008): C07032, doi:10.1029/2007JC004598.
    Beschreibung: This paper examines the sensitivity of atmospheric pCO2 to changes in ocean biology that result in drawdown of nutrients at the ocean surface. We show that the global inventory of preformed nutrients is the key determinant of atmospheric pCO2 and the oceanic carbon storage due to the soft-tissue pump (OCS soft ). We develop a new theory showing that under conditions of perfect equilibrium between atmosphere and ocean, atmospheric pCO2 can be written as a sum of exponential functions of OCS soft . The theory also demonstrates how the sensitivity of atmospheric pCO2 to changes in the soft-tissue pump depends on the preformed nutrient inventory and on surface buffer chemistry. We validate our theory against simulations of nutrient depletion in a suite of realistic general circulation models (GCMs). The decrease in atmospheric pCO2 following surface nutrient depletion depends on the oceanic circulation in the models. Increasing deep ocean ventilation by increasing vertical mixing or Southern Ocean winds increases the atmospheric pCO2 sensitivity to surface nutrient forcing. Conversely, stratifying the Southern Ocean decreases the atmospheric CO2 sensitivity to surface nutrient depletion. Surface CO2 disequilibrium due to the slow gas exchange with the atmosphere acts to make atmospheric pCO2 more sensitive to nutrient depletion in high-ventilation models and less sensitive to nutrient depletion in low-ventilation models. Our findings have potentially important implications for both past and future climates.
    Beschreibung: While at MIT, I.M. was supported by the NOAA Postdoctoral Program in Climate and Global Change, administered by the University Corporation for Atmospheric Research.
    Schlagwort(e): Carbon cycle ; Preformed nutrient ; Nutrient depletion
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  • 11
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    Inverse estimates of anthropogenic CO2 uptake, transport, and storage by the ocean (2010)
    American Geophysical Union
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    Publikationsdatum: 2022-05-26
    Beschreibung: Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 20 (2006): GB2002, doi:10.1029/2005GB002530.
    Beschreibung: Regional air-sea fluxes of anthropogenic CO2 are estimated using a Green's function inversion method that combines data-based estimates of anthropogenic CO2 in the ocean with information about ocean transport and mixing from a suite of Ocean General Circulation Models (OGCMs). In order to quantify the uncertainty associated with the estimated fluxes owing to modeled transport and errors in the data, we employ 10 OGCMs and three scenarios representing biases in the data-based anthropogenic CO2 estimates. On the basis of the prescribed anthropogenic CO2 storage, we find a global uptake of 2.2 ± 0.25 Pg C yr−1, scaled to 1995. This error estimate represents the standard deviation of the models weighted by a CFC-based model skill score, which reduces the error range and emphasizes those models that have been shown to reproduce observed tracer concentrations most accurately. The greatest anthropogenic CO2 uptake occurs in the Southern Ocean and in the tropics. The flux estimates imply vigorous northward transport in the Southern Hemisphere, northward cross-equatorial transport, and equatorward transport at high northern latitudes. Compared with forward simulations, we find substantially more uptake in the Southern Ocean, less uptake in the Pacific Ocean, and less global uptake. The large-scale spatial pattern of the estimated flux is generally insensitive to possible biases in the data and the models employed. However, the global uptake scales approximately linearly with changes in the global anthropogenic CO2 inventory. Considerable uncertainties remain in some regions, particularly the Southern Ocean.
    Beschreibung: This research was financially supported by the National Aeronautics and Space Administration under grant NAG5- 12528. N. G. also acknowledges support by the National Science Foundation (OCE-0137274). Climate and Environmental Physics, Bern acknowledges support by the European Union through the Integrated Project CarboOcean and the Swiss National Science Foundation.
    Schlagwort(e): Anthropogenic CO2 ; Carbon cycle ; Inverse modeling
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  • 12
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    Interannual variations in continental-scale net carbon exchange and sensitivity to observing networks estimated from atmospheric CO2 inversions for the period 1980 to 2005 (2010)
    American Geophysical Union
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    Publikationsdatum: 2022-05-26
    Beschreibung: Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 22 (2008): GB3025, doi:10.1029/2007GB003082.
    Beschreibung: Interannually varying net carbon exchange fluxes from the TransCom 3 Level 2 Atmospheric Inversion Intercomparison Experiment are presented for the 1980 to 2005 time period. The fluxes represent the model mean, net carbon exchange for 11 land and 11 ocean regions after subtraction of fossil fuel CO2 emissions. Both aggregated regional totals and the individual regional estimates are accompanied by a model uncertainty and model spread. We find that interannual variability is larger on the land than the ocean, with total land exchange correlated to the timing of both El Niño/Southern Oscillation (ENSO) as well as the eruption of Mt. Pinatubo. The post-Pinatubo negative flux anomaly is evident across much of the tropical and northern extratropical land regions. In the oceans, the tropics tend to exhibit the greatest level of interannual variability, while on land, the interannual variability is slightly greater in the tropics and northern extratropics. The interannual variation in carbon flux estimates aggregated by land and ocean across latitudinal bands remains consistent across eight different CO2 observing networks. The interannual variation in carbon flux estimates for individual flux regions remains mostly consistent across the individual observing networks. At all scales, there is considerable consistency in the interannual variations among the 13 participating model groups. Finally, consistent with other studies using different techniques, we find a considerable positive net carbon flux anomaly in the tropical land during the period of the large ENSO in 1997/1998 which is evident in the Tropical Asia, Temperate Asia, Northern African, and Southern Africa land regions. Negative anomalies are estimated for the East Pacific Ocean and South Pacific Ocean regions. Earlier ENSO events of the 1980s are most evident in southern land positive flux anomalies.
    Schlagwort(e): Carbon cycle ; Atmospheric inversion ; Interannual variability
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