We explore the representation of the Atlantic Meridional Overturning Circulation (AMOC) in 27 models from the CMIP6 multimodel ensemble. Comparison with RAPID and SAMBA observations suggests that the ...ensemble mean represents the AMOC strength and vertical profile reasonably well. Linear trends over the entire historical period (1850–2014) are generally neutral, but many models exhibit an AMOC peak around the 1980s. Ensemble mean AMOC decline in future (SSP) scenarios is stronger in CMIP6 than CMIP5 models. In fact, AMOC decline in CMIP6 is surprisingly insensitive to the scenario at least up to 2060. We find an emergent relationship among a majority of models between AMOC strength and 21st century AMOC decline. Constraining this relationship with RAPID observations suggests that the AMOC might decline between 6 and 8 Sv (34–45%) by 2100. A smaller group of models projects much less AMOC weakening of only up to 30%.
Plain Language Summary
The Atlantic Meridional Overturning Circulation (AMOC) is a circulation pattern in the Atlantic Ocean that is an important component of the climate system, due to its ability to redistribute and sequester heat and carbon. An accurate representation of the AMOC is a critical test for climate models and essential for building confidence in their projections. Here we investigate the AMOC in 27 climate models that contributed simulations to the Coupled Model Intercomparison Project Phase 6 (CMIP6). We find that many models reproduce the observed AMOC quite well, but there are still several models in which the AMOC is too weak or too strong. Most models suggest a slight upward trend in the AMOC from 1850 to the 1980s. Simulations representing different scenarios for future socioeconomic development suggest a stronger AMOC decline compared to previous assessments. Using direct measurements of the AMOC since 2004 and an emerging across‐model relationship between AMOC decline in the 21st century and their present‐day mean state, we find that the majority of CMIP6 models point to an end of century AMOC weakening of 34–45% of its present‐day strength. A smaller group of models projects much less weakening of only up to 30% of its present state.
Key Points
AMOC mean strength is well reproduced by the CMIP6 multimodel mean, but large model spread persists
Projected AMOC decline by the end of the 21st century shows weak dependence on the SSP scenarios
An emergent constraint between AMOC strength and projected decline suggests possible AMOC decline between 34% and 45% by 2100
We investigate how the ocean response to CO2 forcing affects hemispheric asymmetries in polar climate sensitivity. Intermodel comparison of Phase 5 of the Coupled Model Intercomparison Project CO2 ...quadrupling experiments shows that even in models where hemispheric ocean heat uptake differences are small, Arctic warming still exceeds Antarctic warming. The polar climate impact of this evolving ocean response to CO2 forcing is then isolated using slab ocean experiments in a state‐of‐the‐art climate model. Overall, feedbacks over the Southern Hemisphere more effectively dissipate top‐of‐atmosphere anomalies than those over the Northern Hemisphere. Furthermore, a poleward shift in ocean heat convergence in both hemispheres amplifies destabilizing ice albedo and lapse rate feedbacks over the Arctic much more so than over the Antarctic. These results suggest that the Arctic is intrinsically more sensitive to both CO2 and oceanic forcings than the Antarctic and that ocean‐driven climate sensitivity asymmetry arises from feedback destabilization over the Arctic rather than feedback stabilization over the Antarctic.
Plain Language Summary
Anthropogenic greenhouse gas emissions impact climate globally, but nowhere more so than over the Arctic, a phenomenon known as polar amplification. Surprisingly, the climate response over the Antarctic is much more muted than the climate response over the Arctic, which has been attributed to the large uptake of heat over the Southern Ocean which cools the Southern Hemisphere. Here we show that a weaker climate response over the Antarctic is due, in part, to weaker intrinsic sensitivity to both greenhouse gas forcing and the state of the ocean. Even climate models with similar amounts of heat uptake into the deep ocean in both hemispheres warm more over the Arctic than the Antarctic. Furthermore, similar increases in winter season heat transport into the polar oceans in both hemispheres trigger more destabilizing climate feedbacks over the Arctic than the Antarctic. Therefore, greater climate change over the Arctic than the Antarctic can be expected even if ocean heat uptake or ocean heat transport changes are similar in both hemispheres.
Key Points
The Arctic has greater intrinsic sensitivity to ocean state changes than the Antarctic
The ocean response triggers more destabilizing radiative feedbacks over the Arctic than the Antarctic
Polar radiative feedbacks respond more to increased high‐latitude ocean heat convergence than to subpolar ocean heat uptake
This paper reviewed gender issues on accessibility to agricultural production resources and extension services amongst rural farmers in the predominant crises regions of North-East Nigeria, The study ...applied qualitative analysis in reviewing related literatures, workshop proceedings, seminars, intervention projects, and situation reports on the crisis-torn regions of the Country to elicit cogent facts and figures, The findings revealed that there is a great deal of gender disparity in favour of the men folk as against women and youths in the accessibility to production resources and extension services in the affected regions of the study. This has not only affected their production output but also makes them vulnerable in crisis situations. The paper thus recommends strongly for gender mainstreaming policies towards ensuring equitable access to production resources and extension services in periods of emergencies in these regions. The aftermath is for sustainability in Agricultural production and improvement in rural livelihood to guarantee food security.
This study aimed at evaluating toxicological implications of aqueous P. ostreatus extract (POE) in male Wistar rats. POE was prepared in 1:10 (pulverized P. ostreatus : distilled water). In acute ...toxicity test, single oral dose of 2 mL/kg of POE was administered and observed for 28 days. The sub-chronic toxicity study was conducted by daily oral administration of graded doses (0.25, 0.50 and 0.75 mL/kg b.w) of the extract for 28 days. Clinical signs of toxicity, hematological, serum biochemical parameters and histopathological studies were subsequently evaluated. No treatment-related signs of toxicity or mortality in the animals were recorded in both toxicity tests. Rats administered with lowest dose of POE (25 mL/kg) had highest percentage weight gain. POE had no significant difference (P>0.05) on Red Blood Cell, White Blood Cell (WBC) and differential WBC, and serum biochemistry across all the treated groups when compared to the controls. The result of photomicrographs of stomach, spleen, heart, lung, kidney and liver showed a well outlined arrays of normal tissues in both acute and sub-chronic doses connoting that POE had no toxic effect on them. In view of these, POE may be concluded to be non-toxic within the tested doses and period of investigation.
In this study, attempts were made to immobilize purified exo-inulinase from mutant thermophic Aspergillus tamarii-U4 onto Kaolinite clay by covalent bonding cross-linked with glutaraldehyde with an ...immobilization yield of 66% achieved. The free and immobilized inulinases were then characterized and characterization of the enzymes revealed that temperature and pH optima for the activity of the free and immobilized enzymes were both 65 °C and pH 4.5 respectively. The free inulinase completely lost its activity after incubation at 65 °C for 6 h while the immobilized inulinase retained 16.4% of its activity under the same condition of temperature and incubation time. The estimated kinetic parameters Km and Vmax for the free inulinase as estimated from Lineweaver-Burk plots were 0.39 mM and 4.21 µmol/min for the free inulinase and 0.37 mM and 4.01 µmol/min for the immobilized inulinase respectively. Inulin at 2.5% (w/v) and a flow rate of 0.1 mL was completely hydrolysed for 10 days at 60 °C in a continuous packed bed column and the operational stability of the system revealed that the half-life of the immobilized inulinase was 51 days. These properties make the immobilized exo-inulinase from Aspergillus tamarii-U4 a potential candidate for the production of fructose from inulin hydrolysis.
Limited type A aortic dissection (LTAAD) is a rare subtype of dissection that is confined within a well-defined border of the ascending aorta. These dissections may occur in the remaining native ...portion of the aortic root following aortic root replacement and can be complicated by malperfusion syndrome—a syndrome where dissections compromise the aortic branches and lead to end-organ ischemia. Because LTAAD is confined within the ascending aorta, malperfusion syndrome may preferentially affect the coronary arteries resulting in coronary malperfusion, myocardial infarction, and increased mortality. We report a case of LTAAD and malperfusion syndrome of the left main coronary artery which resulted in inadequate contrast opacification of the aorta and failure of the dissection protocol to trigger on computed tomography (CT). Upon further evaluation of the situation, the radiologist oversaw the manual triggering of CT acquisitions which yielded an actionable CT at 6 minutes post-contrast and real-time visualization of the patient’s developing cardiac ischemia.
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