Inferring the Pattern of the Oceanic Meridional Transport from the Air-Sea Density Flux

The article of record as published may be found at http://dx.doi.org/10.1175/2008JPO3748.1An extension of Walin’s water mass transformation analysis is proposed that would make it possible to assess the strength of the adiabatic along-isopycnal component of the meridional overturning circulation (MOC). It is hypothesized that the substantial fraction of the adiabatic MOC component can be attributed to the difference in subduction rates at the northern and southern outcrops of each density layer—the “push–pull” mechanism. The GCM-generated data are examined and it is shown that the push–pull mode accounts for approximately two-thirds of the isopycnal water mass transport in the global budget and dominates the Atlantic transport. Much of the difference between the actual interhemispheric flux and the push–pull mode can be ascribed to the influence of the Antarctic Circumpolar Current, characterized by the elevated (at least in the GCM) values of the diapycnal transport. When the diagnostic model is applied to observations, it is discovered that the reconstructed MOC is consistent, in terms of the magnitude and sense of overturning, with earlier observational and modeling studies. The findings support the notion that the dynamics of the meridional overturning are largely controlled by the adiabatic processes—time-mean and eddy-induced advection of buoyancy

Residual-mean analysis of the air-sea fluxes and associated oceanic meridional overturning

The dynamic response of the oceanic mixed-layer to the thermodynamic forcing at the sea surface is analyzed in order to describe the pattern of the oceanic meridional overturning. The technique proposed in this study is based on residual-mean theory, which takes into account the transport of buoyancy and tracers by transient eddies. From the observed air-sea density flux and mixed-layer density distributions, we estimate the two components of the Meridional Overturning Circulation (MOC) corresponding to the adiabatic (along-isopycnal) advection and the diabatic (cross-isopycnal) flux. Calculations are performed for the global ocean and, additionally, for each oceanic basin. The proposed method extends the Walin (1982) mass transformation theory, and permits, for the first time, assessment of the strength of the MOC adiabatic component from the sea surface data. This study offers a statistical description of the atmospheric and oceanic databases and gives some suggestions for the choice of specific datasets. In particular, the two most reliable atmospheric climatology databases (ECMWF and NCEP/NCAR re-analyses) are compared, and the impact of their inaccuracies on the MOC calculations is evaluated.http://archive.org/details/residualmeannaly109452513Approved for public release; distribution is unlimited

Inferring the Pattern of the Oceanic Meridional Transport from the Air–Sea Density Flux

Abstract An extension of Walin’s water mass transformation analysis is proposed that would make it possible to assess the strength of the adiabatic along-isopycnal component of the meridional overturning circulation (MOC). It is hypothesized that the substantial fraction of the adiabatic MOC component can be attributed to the difference in subduction rates at the northern and southern outcrops of each density layer—the “push–pull” mechanism. The GCM-generated data are examined and it is shown that the push–pull mode accounts for approximately two-thirds of the isopycnal water mass transport in the global budget and dominates the Atlantic transport. Much of the difference between the actual interhemispheric flux and the push–pull mode can be ascribed to the influence of the Antarctic Circumpolar Current, characterized by the elevated (at least in the GCM) values of the diapycnal transport. When the diagnostic model is applied to observations, it is discovered that the reconstructed MOC is consistent, in terms of the magnitude and sense of overturning, with earlier observational and modeling studies. The findings support the notion that the dynamics of the meridional overturning are largely controlled by the adiabatic processes—time-mean and eddy-induced advection of buoyancy

Influenza- and COVID-19-Associated Pulmonary Aspergillosis: Are the Pictures Different?

International audienceInvasive pulmonary aspergillosis (IPA) in intensive care unit patients is a major concern. Influenza-associated acute respiratory distress syndrome (ARDS) and severe COVID-19 patients are both at risk of developing invasive fungal diseases. We used the new international definitions of influenza-associated pulmonary aspergillosis (IAPA) and COVID-19-associated pulmonary aspergillosis (CAPA) to compare the demographic, clinical, biological, and radiological aspects of IAPA and CAPA in a monocentric retrospective study. A total of 120 patients were included, 71 with influenza and 49 with COVID-19-associated ARDS. Among them, 27 fulfilled the newly published criteria of IPA: 17/71 IAPA (23.9%) and 10/49 CAPA (20.4%). Kaplan-Meier curves showed significantly higher 90-day mortality for IPA patients overall (p = 0.032), whereas mortality did not differ between CAPA and IAPA patients. Radiological findings showed differences between IAPA and CAPA, with a higher proportion of features suggestive of IPA during IAPA. Lastly, a wide proportion of IPA patients had low plasma voriconazole concentrations with a higher delay to reach concentrations > 2 mg/L in CAPA vs. IAPA patients (p = 0.045). Severe COVID-19 and influenza patients appeared very similar in terms of prevalence of IPA and outcome. The dramatic consequences on the patients' prognosis emphasize the need for a better awareness in these particular populations