Validation of a global finite element sea ice-ocean model

Results from a global Finite Element Sea iceOcean Model (FESOM) are evaluated using a wide range of observational datasets. FESOMs ocean component is a primitive-equation, hydrostatic ocean model using isopycnic diffusion and a Gent-McWilliams scheme to parameterize the effects of sub-gridscale turbulence on tracer distribution. Vertical mixing and convection are parameterized as a function of the Richardson number and the Monin-Obukhov length. A finite element dynamic-thermodynamic sea icemodel with elastic-viscous-plastic rheology has been developed and coupled to the ocean component. The model features a prognostic snow layer but neglects internal heat storage. All model components are discretized on a triangular/tetrahedral grid with a continuous, conformingrepresentation of model variables. The coupled model has been run in a global configuration and forced with NCEP daily atmospheric reanalysis data for 1948-2007. Results are analysed with a focus on the Southern Hemisphere. While summer ice extent is underestimated in both hemispheres, winter ice extents are in good agreement with satellite data. Southern Ocean sea ice thickness distribution agrees well with ship-based observations and even quantitatively with data from upwards looking sonars (ULS). Sea ice freezing rates have been validated using repeated salinity profiles from Southern Elephant Seals. Gulf Stream transport is underestimated, but transports of the Kuroshio and the Antarctic Circumpolar Current appear realistic. A comparison of numerical tracer studies to observed CFC distribution indicates that bottom layer ventilation occurs on realistic pathways. Global meridional overturning features a strong Antarctic Bottom Water (AABW) cell, while the formation of North Atlantic Deep Water (NADW) appears to be on the weak side. Besides pure model validation, the study also identifies regions and processes that critically require a locally increased horizontal resolution in order to be represented adequately

Assimilation of Earth rotation parameters into a global ocean model: excitation of polar motion

The oceanic contribution to Earth rotation anomalies can be manifold. Possible causes are a change of total ocean mass, changes in current speed or location and changes in mass distribution. To derive the governing physical mechanisms of oceanic Earth rotation excitation we assimilate Earth rotation observations with a global circulation ocean model. Before assimilation, observations of length of day and polar motion were transformed into estimates of ocean angular momentum. By using the adjoint 4D-VAR assimilation method we were able to reproduce these estimated time series. Although length of day was assimilated simultaneously the analysis in this paper focuses on the oceanic polar motion generation. Our results show that changes in mass distribution and currents contribute to oceanic polar motion generation. Both contributions are highly correlated and show similar amplitudes. The changes in the model done by the assimilation procedure could be related to changes in the atmospheric forcing. Since for geometrical reasons the change of total ocean mass does not project on polar motion, we conclude that the polar motion is mainly generated by a geostrophic response to atmospheric momentum forcing. In geostrophic currents mass displacement and current speed entail each other. This way the large similarity of mass and current generated ocean angular momentum can be explained

Gnosis: Concept, Origin and Context of the "Gnostic movement"

L’article s’inicia amb una discussió sobre la utilitat dels termes “Gnosis” i “Gnosticisme” per explicar l’origen i el desenvolupament de certes conviccions teològiques dels grups en el cristianisme antic. S’ha proposat moltes vegades que aquests termes estan impregnats ideològicament, i per tant més aviat caldria deixar-los de banda entre els estudiosos. Contra això investiguem a fons el significat del terme “Gnosis” en els escrits cristians i filosòfics del segon i tercer segle. Va ser utilitzat com una denominació positiva per al “coneixement veritable”, diferent d’una falsa “anomenada Gnosis”, una expressió esmentada per primera vegada en la primera carta a Timoteu. Des de principis del segle segon dC en endavant “Gnosis” i “Gnostikoi” van ser també utilitzats —principalment en els textos cristians— per a identificar certs mestres i els grups que afirmaven tenir coneixements especials del món transcendent i dels seus misteris. A la tercera part de l’article plantegem l’origen dels ensenyaments més tard anomenats “gnòstics”. Sembla que al principi hi va haver diversos mestres i sistemes que explicaven el missatge cristià amb l’ajuda dels motius filosòfics i mitològics. Això ho il·lustra una mirada més propera en els ensenyaments de Basilides d’Alexandria, Valentí Gnòstic i la seva escola, així com el anomenats “Sethians” un tipus de gnòstics. El “moviment gnòstic” apareix en el cristianisme antic com un intent de fer atractiu el missatge cristià als pagans, mitjançant l’ús d’idees filosòfiques i mitològiques, especialment des del bell mig del Platonisme.The article starts with a discussion of the usefulness oft the terms “Gnosis” and “Gnosticism” for explaining the origin and development of certain theological convictions and groups in ancient Christianity. It was maintained several times that these terms are ideologically loaded and should therefore rather be abandoned in scholarship. Against this background the meanings of the term “Gnosis” in Christian and philosophical writings from the second and third century are investigated. It was used as a positive designation for “true knowledge”, distinguished from a false “so-called Gnosis”, an expression first mentioned in the First letter to Timothy. From the early second century C.E. onwards “Gnosis” and “Gnostikoi” were also used —mainly in Christian texts— to identify certain teachers and groups who claimed to have special knowledge of the transcendent world and its mysteries. The third part of the article asks for the origin of the teachings later called “gnostic”. It appears that at the beginning there were several teachers and systems explaining the Christian message with the help of philosophical and mythological motives. This is illustrated by a closer look at the teachings of Basilides, Valentinus and his school as well as the so-called “Sethian” kind of Gnosticism. The “Gnostic movement” appears as an attempt in ancient Christianity to make the Christian message attractive to pagans by using philosophical and mythological ideas, especially from Middle Platonism

¿Hay un inconsciente político en la tecnología?

The question about whether there is a political unconscious can be understood in two ways. First, it could refer to whether our unconscious (in the Freudian or Lacanian sense) is political. Secondly, the question could mean: are there political (social, economic...) structures, institutions, and processes that are unconscious, in the sense that we do not perceive them “normally” (whatever that means exactly) nor reflect on them? I want to focus on this second meaning and, above all, discuss the question of whether "technology is society made durable" (Latour). In other words: is technology a manifestation of the political unconscious?La cuestión acerca de si existe un inconsciente político puede entenderse de dos maneras. En primer lugar, podría tratarse de si nuestro inconsciente (en el sentido freudiano o lacaniano) es político. En segundo lugar, la pregunta podría significar: ¿existen estructuras, instituciones y procesos políticos (sociales, económicos...) que son inconscientes, en el sentido de que “normalmente” (sea lo que sea que eso signifique exactamente) no los percibimos ni reflexionamos sobre ellos? Quiero centrarme en este segundo significado y, sobre todo, discutir la cuestión de si “la tecnología es la sociedad hecha duradera” (Latour, 1991). Dicho de otro modo: ¿Es la tecnología una manifestación del inconsciente político

Money, Technology and Capitalism in Deleuze’s “Postscript”

“Perhaps it is money that expresses the distinction between the two societies best.” This statement from Deleuze’s (1992: 5) famous “Postscript on the Societies of Control” (first published in French, cf. Deleuze 1990) should be taken seriously. Much has been made of the implications of this essay, especially for the description of contemporary digital culture: e.g., tracking as an example of the “control mechanism, giving the position of any element within an open environment at any given instant” (ibid.: 7). The central role of money and Deleuze’s specific ideas regarding the transformation of capitalism in (or as?) ‘societies of control’ have received comparatively little attention. Seb Franklin (2015: 3-10) has already discussed Deleuze’s famous essay in relation to questions of socio-economic order, but he did not explicitly discuss the role of money. This is all the more surprising if we consider that Deleuze called himself a Marxist: “I think Félix Guattari and I have remained Marxists, in our two different ways, perhaps, but both of us. You see, we think any political philosophy must turn on the analysis of capitalism and the ways it has developed” (Deleuze 1995: 171). Among others, Choat (2010: 125-55) has underlined that Deleuze’s thought was always very close to Marx (cf. also Thoburn 2003). It is therefore not surprising that Deleuze assigns money an important role in the description of control societies

GRACE gravity solutions validated by in-situ ocean bottom pressure in different regions of the global ocean

The GRACE satellite mission provides gravity field estimates of the Earth with unprecedented accuracy. Nevertheless,the realistic detection of oceanic mass redistribution remains challenging due to comparatively small signalamplitude, aliasing by tides and other short-term variability, and smoothing of small spatial scales. To verify thecapability of GRACE to measure oceanic mass variability, a validation with in-situ timeseries of Ocean BottomPressure (OBP) timeseries is essential.Here, different GRACE gravity fields provided by the GRACE Science Data System (CSR, GFZ, JPL), GRGS,ITG and others are compared with more than 140 timeseries of OBP sensors deployed throughout all oceans.The performance of the different GRACE products to capture oceanic mass variability is assessed by a weighedcorrelation analysis, taking into account the length and data quality of the in-situ time series. Both Gaussianfiltering and an ocean-model derived spatial pattern filtering method are used for the GRACE data, whereas forthe in-situ timeseries, different de-tiding and de-trending methods are applied to reduce aliasing and sensor drift.The analysis aims (a) to quantify the skill of different GRACE products and to quantify the advances made byrecent GRACE gravity field releases with improved data processing, and (b) to identify regions where GRACEperforms exceptionally well (e.g. high latitudes), and in which parts of the oceans GRACE fails to detect real OBPvariability. Spatial patterns related to the performance of GRACE may help to predict the quality of spacebornegravity measurements also for those oceanic regions where no in-situ data are available. This is critical for thefuture use of GRACE to remotely determine water mass redistribution in all oceans

A global Ocean Bottom Pressure data base as ground-truth reference for GRACE gravity field products

The GRACE satellite mission provides monthly estimates of the gravity field of the Earth. Differences between the monthly solutions are induced by mass redistribution on the Earth. Over the continents, the hydrological cycle represents the largest signals, which are readily observed by GRACE. Over the oceans, however, gravity field changes are about an order of magnitude smaller, close to the accuracy limits of the present GRACE solutions. Nevertheless, GRACE measurements may prove as an important tool to obtain integral estimates of water mass redistribution, sea level changes and geostrophic current variability. In order to validate and improve the gravity field products, GRACE is to be compared against ocean models and in-situ observations of Ocean Bottom Pressure (OBP). Time series of OBP sensors deployed by Alfred-Wegener-Institut in the Antarctic Circumpolar Current, as well as measurements from other locations of the global ocean are included in a OBP database that is currently under development at AWI, in close cooperation with Proudman Oceanographic Laboratory (POL, Liverpool). The mutual comparison of in-situ and ocean model data with different GRACE products provided by CSR, GFZ, GRGS, ITG and JPL will help to optimize data processing methods and corrections applied to GRACE, and to identify the performance of GRACE to detect oceanic mass flux variability in different regions of the global ocean