Abstract
The Southern Ocean’s Antarctic Circumpolar Current (ACC) and meridional overturning circulation (MOC) response to increasing zonal wind stress is, for the first time, analyzed in a ...high-resolution (0.1° ocean and 0.25° atmosphere), fully coupled global climate simulation using the Community Earth System Model. Results from a 20-yr wind perturbation experiment, where the Southern Hemisphere zonal wind stress is increased by 50% south of 30°S, show only marginal changes in the mean ACC transport through Drake Passage—an increase of 6% 136–144 Sverdrups (Sv; 1 Sv ≡ 10
6
m
3
s
−1
) in the perturbation experiment compared with the control. However, the upper and lower circulation cells of the MOC do change. The lower cell is more affected than the upper cell with a maximum increase of 64% versus 39%, respectively. Changes in the MOC are directly linked to changes in water mass transformation from shifting surface isopycnals and sea ice melt, giving rise to changes in surface buoyancy forcing. The increase in transport of the lower cell leads to upwelling of warm and salty Circumpolar Deep Water and subsequent melting of sea ice surrounding Antarctica. The MOC is commonly supposed to be the sum of two opposing components: a wind- and transient-eddy overturning cell. Here, the transient-eddy overturning is virtually unchanged and consistent with a large-scale cancellation of localized regions of both enhancement and suppression of eddy kinetic energy along the mean path of the ACC. However, decomposing the time-mean overturning into a time- and zonal-mean component and a standing-eddy component reveals partial compensation between wind-driven and standing-eddy components of the circulation.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Background
The aim of this study was to assess heart failure (HF) treatment in patients with and without obesity in a large contemporary real‐world Western European cohort.
Methods
Patients with a ...left ventricular ejection fraction (LVEF) <50% and available information on body mass index (BMI) were selected from the CHECK‐HF registry. The CHECK‐HF registry included chronic HF patients in the period between 2013 and 2016 in 34 Dutch outpatient clinics. Patients were divided into BMI categories. Differences in HF medical treatment were analysed, and multivariable logistic regression analysis (dichotomized as BMI <30 kg/m2 and ≥30 kg/m2) was performed.
Results
Seven thousand six hundred seventy‐one patients were included, 1284 (16.7%) had a BMI ≥30 kg/m2, and 618 (8.1%) had a BMI ≥35 kg/m2. Median BMI was 26.4 kg/m2. Patients with obesity were younger and had a higher rate of comorbidities such as diabetes mellitus, hypertension and obstructive sleep apnoea (OSAS). Prescription rates of guideline‐directed medical therapy (GDMT) increased significantly with BMI. The differences were most pronounced for mineralocorticoid receptor antagonists (MRAs) and diuretics. Patients with obesity more often received the guideline‐recommended target dose. In multivariable logistic regression, obesity was significantly associated with a higher likelihood of receiving ≥100% of the guideline‐recommended target dose of beta‐blockers (OR 1.34, 95% CI 1.10–1.62), renin–angiotensin system (RAS)‐inhibitors (OR 1.34, 95% CI 1.15–1.57) and MRAs (OR 1.40, 95% CI 1.04–1.87).
Conclusions
Guideline‐recommended HF drugs are more frequently prescribed and at a higher dose in patients with obesity as compared to HF patients without obesity.
Present-day control and 1%yr−1increasing carbon dioxide runs have been made using two versions of the Community Climate System Model, version 3.5. One uses the standard versions of the ocean and sea ...ice components where the horizontal resolution is 1° and the effects of mesoscale eddies are parameterized, and the second uses a resolution of
1
10
0
where the eddies are resolved. This is the first time the parameterization has been tested in a climate change run compared to an eddy-resolving run. The comparison is made not straightforward by the fact that the two control run climates are not the same, especially in their sea ice distributions. The focus is on the Antarctic Circumpolar Current region, where the effects of eddies are of leading order. The conclusions are that many of the differences in the two carbon dioxide transient forcing runs can be explained by the different control run sea ice distributions around Antarctica, but there are some quantitative differences in the meridional overturning circulation, poleward heat transport, and zonally averaged heat uptake when the eddies are parameterized rather than resolved.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A decadal climate projection between 1980 and 2030 using a nominal 0.5° resolution in the atmosphere and land components has been performed using the Community Climate System Model, version 3.5. The ...mean climate is compared to a companion simulation using a nominal 2° resolution in the atmosphere and land components. The increased atmosphere resolution has several benefits, and produces a significantly better mean climate. The maximum sea surface temperature biases in the major upwelling regions, including the West Coast of the USA, are reduced by more than 60%. Precipitation patterns are improved in the summer Asian monsoon, mostly due to the better resolved orography, and in the eastern tropical Pacific Ocean south of the equator. The improved precipitation patterns lead to better river flows in many rivers worldwide. The atmospheric circulation in the Arctic also improves, which leads to a better regional sea ice thickness distribution in the Arctic Ocean.
The emergence of a spatial pattern in the externally forced response (FR) of dynamic sea level (DSL) during the altimeter era has recently been demonstrated using climate models but our understanding ...of its initial emergence, drivers, and implications for the future is poor. Here the anthropogenic forcings of the DSL pattern are explored using the Community Earth System Model Large Ensemble (CESM-LE) and Single- Forcing Large Ensemble, a newly available set of simulations where values of individual forcing agents remain fixed at 1920 levels, allowing for an estimation of their effects. Statistically significant contributions to the DSL FR are identified for greenhouse gases (GHGs) and industrial aerosols (AERs), with particularly strong contributions resulting from AERs in the mid-twentieth century and GHGs in the late twentieth and twentyfirst century. Secondary, but important, contributions are identified for biomass burning aerosols in the equatorial Atlantic Ocean in the mid-twentieth century, and for stratospheric ozone in the Southern Ocean during the late twentieth century. Key to understanding regional DSL patterns are ocean heat content and salinity anomalies, which are driven by surface heat and freshwater fluxes, ocean dynamics, and the spatial structure of seawater thermal expansivity. Potential implications for the interpretation of DSL during the satellite era and the longer records from tide gauges are suggested as a topic for future research.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The changes in the Antarctic Circumpolar Current system associated with the Polar, sub-Antarctic and Subtropical Fronts in the Atlantic are examined in a ten-member ensemble using the Community Earth ...System Model. Results for the ensemble average mean show that the Polar Front at 25°W shifts to the south by 0.8° during 1970–2000 compared to its mean latitude over the period 1050–1950. This shift is significant because it is more than twice the standard deviation of the mean latitude time series during 1050–1950. The shift is caused by a slight southward displacement of the Antarctic Circumpolar Current, which in turn is caused by a southward shift in the latitude of the maximum zonal wind stress. The sub-Antarctic Front also shows a small southward shift after 1970, with a maximum latitudinal displacement of 0.2°. However, this shift is not significant compared to the standard deviation of the time series during 1050–1950. The Subtropical Front does not change its latitude during 1970–2000 compared to 1050–2000 because there is very little change in the wind-stress curl in the subtropics. Differences in temperature and salinity throughout the water column at 25°W reveal that during 1970–2000 there is freshening of Antarctic Intermediate Water, whereas the Circumpolar Deep Water becomes saltier.
Background
Elderly patients are underrepresented in clinical trials but comprise the majority of heart failure patients. Data on age-specific use of heart failure therapy are limited. The European ...Society of Cardiology heart failure guidelines provide no age-specific treatment recommendations. We investigated practice-based heart failure management in a large registry at heart failure outpatient clinics.
Design and methods
We studied 8351 heart failure with reduced ejection fraction patients at 34 Dutch outpatient clinics between 2013 and 2016. The mean age was 72.3 ± 11.8 years and we divided age into three categories: less than 60 years (13.9%); 60–74 years (36.0%); and 75 years and over (50.2%).
Results
Elderly heart failure with reduced ejection fraction patients (≥75 years) received significantly fewer beta-blockers (77.8% vs. 84.2%), renin–angiotensin system inhibitors (75.2% vs. 89.7%), mineralocorticoid receptor antagonists (50.6% vs. 59.6%) and ivabradine (2.9% vs. 9.3%), but significantly more diuretics (88.1% vs. 72.6%) compared to patients aged less than 60 years (Pfor all trends < 0.01). Moreover, the prescribed target dosages were significantly lower in elderly patients. Also, implantable cardioverter defibrillator (18.9% vs. 44.1%) and cardiac resynchronisation therapy device (14.6% vs. 16.7%) implantation rates were significantly lower in elderly patients. A similar trend in drug prescription was observed in patients with heart failure with mid-range ejection fraction as in heart failure with reduced ejection fraction.
Conclusion
With increasing age, heart failure with reduced ejection fraction patients less often received guideline-recommended medication prescriptions and also in a lower dosage. In addition, a lower percentage of implantable cardioverter defibrillator and cardiac resynchronisation therapy device implantation in elderly patients was observed.
New features that may affect the behavior of the upper ocean in the Community Climate System Model version 3 (CCSM3) are described. In particular, the addition of an idealized diurnal cycle of solar ...forcing where the daily mean solar radiation received in each daily coupling interval is distributed over 12 daylight hours is evaluated. The motivation for this simple diurnal cycle is to improve the behavior of the upper ocean, relative to the constant forcing over each day of previous CCSM versions. Both 1- and 3-h coupling intervals are also considered as possible alternatives that explicitly resolve the diurnal cycle of solar forcing. The most prominent and robust effects of all these diurnal cycles are found in the tropical oceans, especially in the Pacific. Here, the mean equatorial sea surface temperature (SST) is warmed by as much as 1°C, in better agreement with observations, and the mean boundary layer depth is reduced. Simple rectification of the diurnal cycle explains about half of the shallowing, but less than 0.1°C of the warming. The atmospheric response to prescribed warm SST anomalies of about 1°C displays a very different heat flux signature. The implication, yet to be verified, is that large-scale air–sea coupling is a prime mechanism for amplifying the rectified, daily averaged SST signals seen by the atmosphere. Although the use of upper-layer temperature for SST in CCSM3 underestimates the diurnal cycle of SST, many of the essential characteristics of diurnal cycling within the equatorial ocean are reproduced, including boundary layer depth, currents, and the parameterized vertical heat and momentum fluxes associated with deep-cycle turbulence. The conclusion is that the implementation of an idealized diurnal cycle of solar forcing may make more frequent ocean coupling and its computational complications unnecessary as improvements to the air–sea coupling in CCSM3 continue. A caveat here is that more frequent ocean coupling tends to reduce the long-term cooling trends typical of CCSM3 by heating already too warm ocean depths, but longer integrations are needed to determine robust features. A clear result is that the absence of diurnal solar forcing of the ocean has several undesirable consequences in CCSM3, including too large ENSO variability, much too cold Pacific equatorial SST, and no deep-cycle turbulence.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In contrast to Arctic sea ice, average Antarctic sea ice area is not retreating but has slowly increased since satellite measurements began in 1979. While most climate models from the Coupled Model ...Intercomparison Project Phase 5 (CMIP5) archive simulate a decrease in Antarctic sea ice area over the recent past, whether these models can be dismissed as being wrong depends on more than just the sign of change compared to observations. We show that internal sea ice variability is large in the Antarctic region, and both the observed and modeled trends may represent natural variations along with external forcing. While several models show a negative trend, only a few of them actually show a trend that is significant compared to their internal variability on the time scales of available observational data. Furthermore, the ability of the models to simulate the mean state of sea ice is also important. The representations of Antarctic sea ice in CMIP5 models have not improved compared to CMIP3 and show an unrealistic spread in the mean state that may influence future sea ice behavior. Finally, Antarctic climate and sea ice area will be affected not only by ocean and air temperature changes but also by changes in the winds. The majority of the CMIP5 models simulate a shift that is too weak compared to observations. Thus, this study identifies several foci for consideration in evaluating and improving the modeling of climate and climate change in the Antarctic region.
Key Points
Analysis of modeled historical sea ice behaviour
Focus on internal variability
Few modeled trends are significant
► Climate models using a constant
K will get the wrong response for the future climate. ► Putting limits on parameterization coefficients can compromise results. ► Results are compromised for large ...changes in zonal wind stress if
K has no vertical variation.
The role of the eddy-induced advection coefficient
κ, used in the
Gent and McWilliams (1990) parameterisation (GM), is analysed in terms of the response to idealised wind stress perturbation experiments in the GFDL global coupled climate model CM2.1, and compared to solutions with an eddy-permitting version of the same coupled model, CM2.4. The closure implemented in CM2.1 for
κ is flow-dependent and includes a maximum limit that caps its value. In this paper, we present simulations with a modified version of CM2.1, where the upper limit for
κ is doubled to 1200
m
2
s
−1 and the cap to the isopycnal slope
S
max
in GM is also increased to 1/100 from 1/500. These changes allow their product,
κ S
max
, which is the upper limit to the effect of parameterised eddies, to be an order of magnitude higher than in the original CM2.1 version. Modifications to both GM parameters result in changes in the mean circulation and overall climatology that are non-negligible, which shows that attention has to be paid to the GM implementation during model development. Increasing the value of
κ does produce a stronger compensation between mean and eddy-induced meridional overturning circulations under stronger wind stress forcing, but the residual circulation response is still stronger than in the eddy-permitting model CM2.4. We show that spatially varying
κ, both in the horizontal and vertical directions, is necessary for a correct simulation of the response to changes in the wind stress. New and improved closures for
κ are needed, and should be tested in coupled climate models.
PDF
