Mechanisms controlling the SST air-sea heat flux feedback and its dependence on spatial scale

Author Posting. © The Author(s), 2016. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Climate Dynamics 48 (2017): 1297–1307, doi:10.1007/s00382-016-3142-3.The turbulent air-sea heat flux feedback (α, in W m-2 K-1) is a major contributor to setting the damping timescale of sea surface temperature (SST) anomalies. In this study we compare the spatial distribution and magnitude of α in the North Atlantic and the Southern Ocean, as estimated from the ERA-Interim reanalysis dataset. The comparison is rationalized in terms of an upper bound on the heat flux feedback, associated with \fast" atmospheric export of temperature and moisture anomalies away from the marine boundary layer, and a lower bound associated with "slow" export. It is found that regions of cold surface waters (≤10°C) are best described as approaching the slow export limit. This conclusion is not only valid at the synoptic scale resolved by the reanalysis data, but also on basin scales. In particular, it applies to the heat flux feedback acting as circumpolar SST anomaly scales are approached in the Southern Ocean, with feedbacks of ≤10 W m-2 K-1. In contrast, the magnitude of the heat flux feed-back is close to that expected from the fast export limit over the Gulf Stream and its recirculation with values on the order of ≈40 W m-2 K-1. Further analysis suggests that this high value reflects a compensation between a moderate thermo-dynamic adjustment of the boundary layer, which tends to weaken the heat flux feedback, and an enhancement of the surface winds over warm SST anomalies, which tend to enhance the feedback.Ute Hausmann and John Marshall acknowledge support by the FESD program of NSF.2017-05-0

The signature of mesoscale eddies on sea surface temperature and its associated heat transport

This thesis aims at analysing the impact of oceanic turbulence and air-sea interactions on the sea surface temperature (SST) of the extra-tropical oceans on spatial scales of a few hundred kilometres (the so-called "mesoscale"). Using satellite-based measurements of SST and sea level, as well as surface tracks of mesoscale oceanic cyclones and anticyclones, it is shown that turbulence does not transport heat through systematic motions of cold cyclones and warm anticyclones, as was previously thought in regions of strong mean flows like the Gulf Stream. Rather, it is suggested that heat is transported as a result of the slight phase shift between temperature and pressure fluctuations developing on the mean flow. In addition, tentative estimates of the rate at which air-sea heat fluxes damp the SST signatures of cyclones and anticyclones are provided. The weak values obtained ( 20 W/m2K) contrast sharply with theoretical expectations, but are in agreement with the observed long-lived thermal heat content anomalies associated with the cyclones and anticyclones. These observations provide important benchmarks for high-resolution ocean models and may moreover guide the parametrization of subgrid-scale heat transport in climate models

Observed mesoscale eddy signatures in Southern Ocean surface mixed-layer depth

Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 122 (2017): 617–635, doi:10.1002/2016JC012225.Combining satellite altimetry with Argo profile data a systematic observational estimate of mesoscale eddy signatures in surface mixed-layer depth (MLD) is provided across the Southern Ocean (SO). Eddy composite MLD anomalies are shallow in cyclones, deep in anticyclones, and increase in magnitude with eddy amplitude. Their magnitudes show a pronounced seasonal modulation roughly following the depth of the climatological mixed layer. Weak eddies of the relatively quiescent SO subtropics feature peak late-winter perturbations of ±10 m. Much larger MLD perturbations occur over the vigorous eddies originating along the Antarctic Circumpolar Current (ACC) and SO western boundary current systems, with late-winter peaks of −30 m and +60 m in the average over cyclonic and anticyclonic eddy cores (a difference of ≈ 100 m). The asymmetry between modest shallow cyclonic and pronounced deep anticyclonic anomalies is systematic and not accompanied by corresponding asymmetries in eddy amplitude. Nonetheless, the net deepening of the climatological SO mixed layer by this asymmetry in eddy MLD perturbations is estimated to be small (few meters). Eddies are shown to enhance SO MLD variability with peaks in late winter and eddy-intense regions. Anomalously deep late-winter mixed layers occur disproportionately within the cores of anticyclonic eddies, suggesting the mesoscale heightens the frequency of deep winter surface-mixing events along the eddy-intense regions of the SO. The eddy modulation in MLD reported here provides a pathway via which the oceanic mesoscale can impact air-sea fluxes of heat and carbon, the ventilation of water masses, and biological productivity across the SO.NSF via the MOBY project investigating the impacts of ocean eddies on biogeochemical cycles. In addition, DJM also acknowledges support from NASA.2017-07-2

Kleinfeuerungsanlagen in Sachsen: Anlagenbestand und Emissionen von Kleinfeuerungsanlagen in Sachsen

Der Bericht informiert über den Bestand an Kleinfeuerungsanlagen 2015 in Sachsen. Enthalten sind Daten zu Anzahl, Brennstoff, Kapazität, Bauart, Energieverbrauch, Schadstoffausstoß und Sanierungsfristen. Die Karten und Tabellen stehen für Landkreise und kreisfreie Städte zum Herunterladen zur Verfügung. Weitere Auswertungen stellt das LfULG auf Anforderung bereit. Der Bericht richtet sich an mit Luftreinhaltung oder Klimaschutz befasste Behörden

The ocean's role in polar climate change: asymmetric Arctic and Antarctic responses to greenhouse gas and ozone forcing

In recent decades, the Arctic has been warming and sea ice disappearing. By contrast, the Southern Ocean around Antarctica has been (mainly) cooling and sea-ice extent growing. We argue here that interhemispheric asymmetries in the mean ocean circulation, with sinking in the northern North Atlantic and upwelling around Antarctica, strongly influence the sea-surface temperature (SST) response to anthropogenic greenhouse gas (GHG) forcing, accelerating warming in the Arctic while delaying it in the Antarctic. Furthermore, while the amplitude of GHG forcing has been similar at the poles, significant ozone depletion only occurs over Antarctica. We suggest that the initial response of SST around Antarctica to ozone depletion is one of cooling and only later adds to the GHG-induced warming trend as upwelling of sub-surface warm water associated with stronger surface westerlies impacts surface properties. We organize our discussion around ‘climate response functions’ (CRFs), i.e. the response of the climate to ‘step’ changes in anthropogenic forcing in which GHG and/or ozone-hole forcing is abruptly turned on and the transient response of the climate revealed and studied. Convolutions of known or postulated GHG and ozone-hole forcing functions with their respective CRFs then yield the transient forced SST response (implied by linear response theory), providing a context for discussion of the differing warming/cooling trends in the Arctic and Antarctic. We speculate that the period through which we are now passing may be one in which the delayed warming of SST associated with GHG forcing around Antarctica is largely cancelled by the cooling effects associated with the ozone hole. By mid-century, however, ozone-hole effects may instead be adding to GHG warming around Antarctica but with diminished amplitude as the ozone hole heals. The Arctic, meanwhile, responding to GHG forcing but in a manner amplified by ocean heat transport, may continue to warm at an accelerating rate

Die Wiederbelebung der Scheintoten: zur Kritik der Animation

Es geht um die Bedeutung der auf weite Lebensbereiche expandierten Animation als sozialer Kontrolle. Die ursprünglich nur in der Urlaubsgestaltung kurzfristig angewandte Animation weitet sich zu langfristig intendierter Beeinflussung der Gestaltung von Wohn- und Lebensverhältnissen aus durch die Vorgabe architektonischer Strukturen und sozialer Verhaltensmuster durch Sozialarbeiter- und bevölkerungsnahe Polizeitätigkeit. Sie ist dem Taylorismus, der die Beeinflussung und Kontrolle des Arbeitsverhaltens fordert, vergleichbar. Das Ziel der Animation besteht in sozialkultureller Aufbauarbeit, die die Kreativität und Selbstentfaltung des einzelnen in durch Selbstkontrolle geregeltem sozialem Handlungsfeld sichert, was gleichzeitig die Einschränkung persönlicher Freiheit durch die vorgegebenen, erwünschten Verhaltens- und Handlungsmuster bedeutet. (HD

Unsupervised classification identifies coherent thermohaline structures in the Weddell Gyre region

The Weddell Gyre is a major feature of the Southern Ocean and an important component of the planetary climate system; it regulates air–sea exchanges, controls the formation of deep and bottom waters, and hosts upwelling of relatively warm subsurface waters. It is characterised by low sea surface temperatures, ubiquitous sea ice formation, and widespread salt stratification that stabilises the water column. Observing the Weddell Gyre is challenging, as it is extremely remote and largely covered with sea ice. At present, it is one of the most poorly sampled regions of the global ocean, highlighting the need to extract as much value as possible from existing observations. Here, we apply a profile classification model (PCM), which is an unsupervised classification technique, to a Weddell Gyre profile dataset to identify coherent regimes in temperature and salinity. We find that, despite not being given any positional information, the PCM identifies four spatially coherent thermohaline domains that can be described as follows: (1) a circumpolar class, (2) a transition region between the circumpolar waters and the Weddell Gyre, (3) a gyre edge class with northern and southern branches, and (4) a gyre core class. PCM highlights, in an objective and interpretable way, both expected and underappreciated structures in the Weddell Gyre dataset. For instance, PCM identifies the inflow of Circumpolar Deep Water (CDW) across the eastern boundary, the presence of the Weddell–Scotia Confluence waters, and structured spatial variability in mixing between Winter Water and CDW. PCM offers a useful complement to existing expertise-driven approaches for characterising the physical configuration and variability of oceanographic regions, helping to identify coherent thermohaline structures and the boundaries between them

Fast and slow responses of Southern Ocean sea surface temperature to SAM in coupled climate models

We investigate how sea surface temperatures (SSTs) around Antarctica respond to the Southern An- nular Mode (SAM) on multiple timescales. To that end we examine the relationship between SAM and SST within unperturbed preindustrial control simulations of coupled general circulation models (GCMs) included in the Climate Modeling Intercomparison Project phase 5 (CMIP5). We develop a technique to extract the re- sponse of the Southern Ocean SST (55◦S−70◦S) to a hypothetical step increase in the SAM index. We demonstrate that in many GCMs, the expected SST step re- sponse function is nonmonotonic in time. Following a shift to a positive SAM anomaly, an initial cooling regime can transition into surface warming around Antarctica. However, there are large differences across the CMIP5 ensemble. In some models the step response function never changes sign and cooling persists, while in other GCMs the SST anomaly crosses over from negative to positive values only three years after a step increase in the SAM. This intermodel diversity can be related to differences in the models’ climatological thermal ocean stratification in the region of seasonal sea ice around Antarctica. Exploiting this relationship, we use obser- vational data for the time-mean meridional and vertical temperature gradients to constrain the real Southern Ocean response to SAM on fast and slow timescales

Kleinfeuerungsanlagen in Sachsen: Anlagenbestand und Emissionen von Kleinfeuerungsanlagen in Sachsen

Der Bericht informiert über den Bestand an Kleinfeuerungsanlagen 2015 in Sachsen. Enthalten sind Daten zu Anzahl, Brennstoff, Kapazität, Bauart, Energieverbrauch, Schadstoffausstoß und Sanierungsfristen. Die Karten und Tabellen stehen für Landkreise und kreisfreie Städte zum Herunterladen zur Verfügung. Weitere Auswertungen stellt das LfULG auf Anforderung bereit. Der Bericht richtet sich an mit Luftreinhaltung oder Klimaschutz befasste Behörden

Predominant Sea Ice Fracture Zones Around Antarctica and Their Relation to Bathymetric Features

Sea ice is of substantial importance for the Southern Ocean, as it insulates the relatively warm ocean from the cold atmosphere. Due to mechanical stress induced by wind and ocean currents, sea ice leads occur, which are characterized by open water and thin ice causing an increase of energy and moisture fluxes between ocean and atmosphere. Furthermore, they contribute to the ice production and provide a habitat for animals. Thus, it is important to gain information about the temporal and spatial distribution of leads on a circum-Antarctic scale. So far, no operational data set exists, which provides such information. We use thermal satellite imagery from the Moderate Resolution Imaging Spectroradiometer to derive the predominant lead patterns for 2003-2018, April-September. This study provides first results for the long-term average lead frequencies in the Southern Ocean and discusses possible links to ocean currents, tides, and the bathymetry. Plain Language Summary The polar regions are strongly influenced by sea ice, which covers large areas of the ocean's surface. Interacting with the atmosphere and the ocean, sea ice is a very dynamic surface with a large temporal and spatial variability. Under the forcing of winds and ocean currents, sea ice is subject to deformation processes causing cracks (leads) in the ice. The observation of these leads is the aim of this study since they are an important feature. For instance, open water can be found in these cracks, which enables the warm ocean (−1.7 • C) to lose energy to the cold atmosphere. Also, sea ice forms a habitat for animals. In this study, the focus is on the Southern Hemisphere where sea ice surrounds the Antarctic continent. For the winter months, we use thermal infrared satellite images where leads appear as warm, almost linear features compared to the cold ice cover. By using computer algorithms, the cracks are detected automatically. This is the first study that shows these features in the Southern Ocean. Leads not only exist close to the coastline but also tend to appear offshore with characteristic spatial patterns. Therefore, possible links to ocean currents, tides, and bathymetry are discussed