Stratospheric aerosols from large tropical explosive volcanic eruptions backscatter shortwave radiation and reduce the global mean surface temperature. Observations suggest that they also favour an ...El Niño within 2 years following the eruption. Modelling studies have, however, so far reached no consensus on either the sign or physical mechanism of El Niño response to volcanism. Here we show that an El Niño tends to peak during the year following large eruptions in simulations of the Fifth Coupled Model Intercomparison Project (CMIP5). Targeted climate model simulations further emphasize that Pinatubo-like eruptions tend to shorten La Niñas, lengthen El Niños and induce anomalous warming when occurring during neutral states. Volcanically induced cooling in tropical Africa weakens the West African monsoon, and the resulting atmospheric Kelvin wave drives equatorial westerly wind anomalies over the western Pacific. This wind anomaly is further amplified by air-sea interactions in the Pacific, favouring an El Niño-like response.El Niño tends to follow 2 years after volcanic eruptions, but the physical mechanism behind this phenomenon is unclear. Here the authors use model simulations to show that a Pinatubo-like eruption cools tropical Africa and drives westerly wind anomalies in the Pacific favouring an El Niño response.
The implementation of boundary conditions is a key aspect of climate simulations. We describe here how the Climate Model Intercomparison Project Phase 6 (CMIP6) forcing data sets have been processed ...and implemented in Version 6 of the Institut Pierre‐Simon Laplace (IPSL) climate model (IPSL‐CM6A‐LR) as used for CMIP6. Details peculiar to some of the Model Intercomparison Projects are also described. IPSL‐CM6A‐LR is run without interactive chemistry; thus, tropospheric and stratospheric aerosols as well as ozone have to be prescribed. We improved the aerosol interpolation procedure and highlight a new methodology to adjust the ozone vertical profile in a way that is consistent with the model dynamical state at the time step level. The corresponding instantaneous and effective radiative forcings have been estimated and are being presented where possible.
Plain Language Summary
Climate Model Intercomparison Project Phase 6 is an international project to compare the results from climate model simulations performed according to a common protocol. Such simulations require boundary conditions (called “climate forcings”), which are fed to the models in order to represent, for example, long‐lived greenhouse gases, ozone, atmospheric aerosols, or land surface properties. The same forcing data sets are used by the different modeling groups who carry out the Climate Model Intercomparison Project Phase 6 simulations; however, their implementation may differ as it depends on the model structure. This article gives details of how these forcing data were implemented in the IPSL‐CM6A‐LR model. Some of the forcing data are common to all types all simulations, whereas others depend on the runs considered. Radiative forcings, as estimated in the model, are presented for some of the forcing mechanisms.
Key Points
We present how the CMIP6 forcing data were implemented in the IPSL‐CM6A‐LR climate model for the realization of the CMIP6 set of climate simulations
An improved conservative interpolation procedure for emissions is detailed and illustrated to compute tropospheric aerosols
We present a new methodology to adjust the prescribed ozone vertical profile to match the model atmospheric dynamical state around the tropopause
The original version of this Article omitted a reference to previous work in 'Mann, M.E., Cane, M.A., Zebiak, S.E., Clement, A., Volcanic and Solar Forcing of the Tropical Pacific Over the Past 1000 ...Years, J. Climate 18, 447-456 (2005)'. This has been added as reference 62 at the end of the fourth sentence of the fourth paragraph of the Introduction: 'Early studies using simple coupled ocean-atmosphere models
proposed that following volcano-induced surface cooling, upwelling in the eastern equatorial Pacific acting on a reduced vertical temperature contrast between the ocean surface and interior leads to anomalous warming in this region, thereby favouring El Niño development the following year
.' This has been corrected in the PDF and HTML versions of the Article.
In a warming world context, sea surface temperature (SST) off central-south Peru, northern Chile, and farther offshore increases at a slower rate than the global average since several decades (i.e., ...cools, relative to the global average). This tendency is synchronous with an interdecadal Pacific oscillation (IPO) negative trend since ∼1980, which has a cooling signature in the southeastern Pacific. Here, we use a large ensemble of historical coupled model simulations to investigate the relative roles of internal variability (and in particular the IPO) and external forcing in driving this relative regional cooling, and the associated mechanisms. The ensemble mean reproduces the relative cooling, in response to an externally forced southerly wind anomaly, which strengthens the upwelling off Chile in recent decades. This southerly wind anomaly results from the poleward expansion of the Southern Hemisphere Hadley cell. Attribution experiments reveal that this poleward expansion and the resulting enhanced upwelling mostly occur in response to increasing greenhouse gases and stratospheric ozone depletion since ∼1980. An oceanic heat budget confirms that the wind-forced upwelling enhancement dominates the relative cooling near the coast. In contrast, a wind-forced deepening of the mixed layer drives the offshore cooling. While internal variability contributes to the spread of tendencies, the ensemble-mean relative cooling in the southeastern Pacific is consistent with observations and occurs irrespectively of the IPO phase, hence, indicating the preeminent role of external forcing.
Tumor hypoxia is a hallmark of malignant tumors, and is a major factor in the resistance to anti-cancer therapies, particularly radiotherapy. Indeed, tumor blood flow often fluctuates, and thus the ...oxygen supply is often reduced, thereby inducing tumor hypoxia. We decided to explore whether post-occlusive reactive hyperemia, a physiological reaction known to occur in normal tissues, could be induced through a malignant tumor, basal cell carcinoma (BCC), in which angiogenesis occurs, as in all malignant tumors. Skin blood flow was measured in twelve patients with BCC, using Laser Speckle Contrast Imaging to determine BCC perfusion after three minutes of vascular occlusion, induced by limb tourniquet for limb tumors (4 BCC), and/or by clamping the pedicle of a skin flap with the BCC at its center, for other tumor locations (12 BCC). We demonstrated for the first time that post-occlusive reactive hyperemia occurs in malignant tumors in humans. BCC perfusion curves were similar to those of healthy skin, characterized by a peak of hyperemia after reperfusion followed by a progressive return to the pre-occlusion perfusion level. Induction of post-occlusive reactive hyperemia in malignant tumors is therefore a novel investigational approach that could lead to a new adjuvant tool to increase the efficacy of chemotherapy and radiotherapy, respectively through the synchronized temporary increase of tumor perfusion and oxygenation.
This paper provides initial results from a multi-model ensemble analysis based on the volc-pinatubo-full experiment performed within the Model Intercomparison Project on the climatic response to ...Volcanic forcing (VolMIP) as part of the sixth phase of the Coupled Model Intercomparison Project (CMIP6). The volc-pinatubo-full experiment is based on an ensemble of volcanic forcing-only climate simulations with the same volcanic aerosol dataset across the participating models (the 1991-1993 Pinatubo period from the CMIP6-GloSSAC dataset). The simulations are conducted within an idealized experimental design where initial states are sampled consistently across models from the CMIP6-piControl simulation providing unperturbed preindustrial background conditions. The multi-model ensemble includes output from an initial set of six participating Earth system models (CanESM5, GISS-E2.1-G, IPSL-CM6A-LR, MIROC-E2SL, MPI-ESM1.2-LR and UKESM1).
Direct observations indicate a southeastward expansion of the South Pacific convergence zone (SPCZ) fresh pool and a freshening trend since the 1970s. Understanding decadal and longer-term ...variability of the SPCZ fresh pool and of the salinity front located at its southeastern margin has been limited by the scarcity of instrumental sea surface salinity (SSS) measurements. This study uses coral δ
18 O as a proxy for SSS to extend the salinity record back to the 1880s, from three different locations across the SSS front: Fiji, Tonga, and Rarotonga (FTR region). High percentages of observed SSS variance are explained by multicoral δ
18 O mean composite at each site. At the interannual time scale, the salinity front displacement over the last 200 years follows the El Niño–Southern Oscillation (ENSO) index. The different El Niño flavors are observable in the amplitude of the salinity front interannual displacement. However, no significant changes in either the frequency or the amplitude of its displacements were observed. At longer time scales, the timing and magnitude of the freshening trend vary among sites. The earliest freshening onset of about −0.06 psu decade−1 is detected in Fiji (around 1865), then Rarotonga (around 1939), and Tonga (around 1982). The role of atmospheric freshwater fluxes on SSS variability is evaluated by comparing coral SSS to historical precipitation data. The results suggest that, despite the known influence of the interdecadal Pacific oscillation (IPO) negative phases on increasing atmospheric freshwater fluxes and lowering SSS in the FTR region, ocean dynamics has a dominant influence at decadal time scale and in the onset of freshening trends.
δ18O and δD of fluid inclusions in carbonates provide insights into temperatures and fluid chemical compositions prevailing during the carbonate precipitation, however, various analytical ...restrictions limit a wider application of this proxy. This paper presents a new fluid inclusions isotopic analytical line coupled to an online cavity ring‐down spectrometer that increased the analytical productivity up to 10 carbonate samples per working day. This efficiency allowed for the first time to assess the reliability a large set of water samples with size ranging from 0.1 to 1 µL. Good reproducibility (±0.5‰ for δ18O and ± 2‰ δD; 1σ) is obtained for water quantity superior or equal to 0.3 μL and no evidence of memory effect is found. The line is further tested using two types of natural carbonates: (1) modern speleothems samples from caves for which δ18O and δD values of drip water were measured and (2) diagenetic carbonates for which the δ18O of the parent water were independently back‐calculated from carbonate clumped isotope Δ47 measurements. Speleothem fluid inclusion values despite falling close to the Global Meteoritic Water Line are not always representative of the isotopic composition of the parent drip water. Results on diagenetic cements show that the δ18Owater values measured in fluid inclusions agree, within 1%, with the δ18Owater independently derived from Δ47 measurements. Overall, this study confirms the reliability and accuracy of the developed analytical line for carbonate fluid inclusion analyses with a good reproducibility obtained for water quantity above 0.3 μL.
Key Points
A new fluid inclusion analytical line with a productivity up to 10 carbonate isotopic measurements per working day
A new reliable and accurate fluid inclusion analytical line for δ18O and δD fluid inclusion analyses in carbonates
Fluid inclusion δ18O of diagenetic cements agree, within 1‰, with the δ18O independently derived from Δ47 measurements
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