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Author  |
Zou, M.; Xiong, X.; Wu, Z.; Li, S.; Zhang, Y.; Chen, L. | ||||
| Title | Increase of Atmospheric Methane Observed from Space-Borne and Ground-Based Measurements | Type | $loc['typeJournal Article'] | ||
| Year | 2019 | Publication | Remote Sensing | Abbreviated Journal | Remote Sensing |
| Volume | 11 | Issue | 8 | Pages | |
| Keywords | Methane increase trend; Boundary layer; Mid-upper troposphere; Satellite; AIRS | ||||
| Abstract | It has been found that the concentration of atmospheric methane (CH4) has rapidly increased since 2007 after a decade of nearly constant concentration in the atmosphere. As an important greenhouse gas, such an increase could enhance the threat of global warming. To better quantify this increasing trend, a novel statistic method, i.e. the Ensemble Empirical Mode Decomposition (EEMD) method, was used to analyze the CH4 trends from three different measurements: the mid-upper tropospheric CH4 (MUT) from the space-borne measurements by the Atmospheric Infrared Sounder (AIRS), the CH4 in the marine boundary layer (MBL) from NOAA ground-based in-situ measurements, and the column-averaged CH4 in the atmosphere (X-CH4) from the ground-based up-looking Fourier Transform Spectrometers at Total Carbon Column Observing Network (TCCON) and the Network for the Detection of Atmospheric Composition Change (NDACC). Comparison of the CH4 trends in the mid-upper troposphere, lower troposphere, and the column average from these three data sets shows that, overall, these trends agree well in capturing the abrupt CH4 increase in 2007 (the first peak) and an even faster increase after 2013 (the second peak) over the globe. The increased rates of CH4 in the MUT, as observed by AIRS, are overall smaller than CH4 in MBL and the column-average CH4. During 2009-2011, there was a dip in the increase rate for CH4 in MBL, and the MUT-CH4 increase rate was almost negligible in the mid-high latitude regions. The increase of the column-average CH4 also reached the minimum during 2009-2011 accordingly, suggesting that the trends of CH4 are not only impacted by the surface emission, however that they also may be impacted by other processes like transport and chemical reaction loss associated with [OH]. One advantage of the EEMD analysis is to derive the monthly rate and the results show that the frequency of the variability of CH4 increase rates in the mid-high northern latitude regions is larger than those in the tropics and southern hemisphere. | ||||
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| Language | Summary Language | Original Title | |||
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| Series Volume | Series Issue | Edition | |||
| ISSN | 2072-4292 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Funding | Approved | $loc['no'] | |||
| Call Number | COAPS @ user @ | Serial | 1055 | ||
| Permanent link to this record | |||||
| Author |
Zou, S.; Bower, A.; Furey, H.; Susan Lozier, M.; Xu, X. | ||||
| Title | Redrawing the Iceland-Scotland Overflow Water pathways in the North Atlantic | Type | $loc['typeJournal Article'] | ||
| Year | 2020 | Publication | Abbreviated Journal | Nat Commun | |
| Volume | 11 | Issue | 1 | Pages | 1890 |
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| Abstract | Iceland-Scotland Overflow Water (ISOW) is a primary deep water mass exported from the Norwegian Sea into the North Atlantic as part of the global Meridional Overturning Circulation. ISOW has historically been depicted as flowing counter-clockwise in a deep boundary current around the subpolar North Atlantic, but this single-boundary-following pathway is being challenged by new Lagrangian observations and model simulations. We show here that ISOW leaves the boundary and spreads into the interior towards the central Labrador and Irminger basins after flowing through the Charlie-Gibbs Fracture Zone. We also describe a newly observed southward pathway of ISOW along the western flank of the Mid-Atlantic Ridge. The partitioning of these pathways is shown to be influenced by deep-reaching eddies and meanders of the North Atlantic Current. Our results, in tandem with previous studies, call for a revision in the historical depiction of ISOW pathways throughout the North Atlantic. | ||||
| Address | Center for Ocean-Atmosphere Prediction Studies, Florida State University, Tallahassee, FL, USA | ||||
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| Language | English | Summary Language | Original Title | ||
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| Series Volume | Series Issue | Edition | |||
| ISSN | 2041-1723 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Funding | strtoupper('3').strtolower('2313002'); strtoupper('P').strtolower('MC7170894') | Approved | $loc['no'] | ||
| Call Number | COAPS @ user @ | Serial | 1105 | ||
| Permanent link to this record | |||||
| Author |
Zou, S.; Lozier, M.S.; Xu, X. | ||||
| Title | Latitudinal Structure of the Meridional Overturning Circulation Variability on Interannual to Decadal Time Scales in the North Atlantic Ocean | Type | $loc['typeJournal Article'] | ||
| Year | 2020 | Publication | Journal of Climate | Abbreviated Journal | J. Climate |
| Volume | 33 | Issue | 9 | Pages | 3845-3862 |
| Keywords | Deep convection; Ocean circulation; Thermocline circulation | ||||
| Abstract | The latitudinal structure of the Atlantic meridional overturning circulation (AMOC) variability in the North Atlantic is investigated using numerical results from three ocean circulation simulations over the past four to five decades. We show that AMOC variability south of the Labrador Sea (53°N) to 25°N can be decomposed into a latitudinally coherent component and a gyre-opposing component. The latitudinally coherent component contains both decadal and interannual variabilities. The coherent decadal AMOC variability originates in the subpolar region and is reflected by the zonal density gradient in that basin. It is further shown to be linked to persistent North Atlantic Oscillation (NAO) conditions in all three models. The interannual AMOC variability contained in the latitudinally coherent component is shown to be driven by westerlies in the transition region between the subpolar and the subtropical gyre (40°–50°N), through significant responses in Ekman transport. Finally, the gyre-opposing component principally varies on interannual time scales and responds to local wind variability related to the annual NAO. The contribution of these components to the total AMOC variability is latitude-dependent: 1) in the subpolar region, all models show that the latitudinally coherent component dominates AMOC variability on interannual to decadal time scales, with little contribution from the gyre-opposing component, and 2) in the subtropical region, the gyre-opposing component explains a majority of the interannual AMOC variability in two models, while in the other model, the contributions from the coherent and the gyre-opposing components are comparable. These results provide a quantitative decomposition of AMOC variability across latitudes and shed light on the linkage between different AMOC variability components and atmospheric forcing mechanisms. | ||||
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| Language | Summary Language | Original Title | |||
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| Series Volume | Series Issue | Edition | |||
| ISSN | 0894-8755 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Funding | Approved | $loc['no'] | |||
| Call Number | COAPS @ user @ | Serial | 1106 | ||
| Permanent link to this record | |||||
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