Thermal regime and spatial variability of the active layer in Deception Island, Antarctica

El programa de monitoreo de capa activa (CALM) fue desarrollado en las últimas décadas con la finalidad de comprender el impacto del cambio climático sobre los ambientes con permafrost. Este trabajo analiza los resultados obtenidos, en los últimos seis años, de los sitios CALM-S Irizar, Cráter Lake y Refugio Chileno, ubicados en Isla Decepción. En ellos se ha medido el espesor, el estado térmico y la distribución espacial de la capa activa. En los sitios Irizar y Refugio Chileno la evolución del espesor de capa activa varió interanualmente sin una clara tendencia dentro del corto período analizado; por el contrario, el sitio Cráter Lake evidenció una tendencia a la disminución de espesor. La distribución espacial como el espesor de dicha capa en los tres sitios de monitoreo, mostraron estar condicionados principalmente por la potencia de la cubierta de nieve, la litología y la exposición a los vientos. El relieve, la topografía de detalle, la orientación de las laderas frente a la radiación solar incidente, ejercieron un control menor sobre esta distribución. El estado térmico de la capa activa evidenció el control ejercido sobre ella de la temperatura del aire y de la cubierta nival. Así bajo reducidos espesores de nieve, el modelo de penetración en profundidad de la isoterma de 0 ºC, ha permitido aproximar satisfactoriamente el espesor de capa activa.The Circumpolar Active Layer Monitoring (CALM) program developed over the last two decades has a leading edge in comprehensive efforts to study the impacts of climate change in permafrost environments. This paper describes results obtained during the last six years, on the active layer thickness, thermal regime and spatial patterns of thaw, at the CALM-S Irizar, Crater Lake and Refugio Chileno sites in Deception Island. In Irizar and Refugio Chileno CALM-S sites the active layer depth varied interannually without any clear trend over the short record available. By contrast, Crater Lake CALM-S showed a slight thinning trend. In all sites, the spatial patterns of thaw and active layer thickness were mainly controlled by snow cover conditions, lithology and the effect of aspect on wind. The relief, the detailed topography and the effect of aspect on solar radiation also exert a local control over its patterns. Air temperature and snow cover controlled the thermal state of active layer. In absence of snow, the use of depth penetration model of the 0 ºC isotherm allowed approximated satisfactorily active layer thickness.Fil: Goyanes, Gabriel Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Vieira, Gonçalo. Universidad de Lisboa; PortugalFil: Caselli, Alberto Tomás. Universidad Nacional de Río Negro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Mora, Carla. Universidad de Lisboa; PortugalFil: Ramos, Miguel Esteban. Universidad de Alcalá; España. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: de Pablo, Miguel Angel. Universidad de Alcalá; EspañaFil: Neves, Mario. Universidad de Lisboa; PortugalFil: Santos, Fernando. Universidad de Lisboa; PortugalFil: Bernardo, Ivo. Universidad de Lisboa; PortugalFil: Gilichinsky, David. Academia Rusa de Ciencias; RusiaFil: Abramov, Andrey. Academia Rusa de Ciencias; RusiaFil: Batista, Vanessa. Universidad de Lisboa; PortugalFil: Melo, Raquel. Universidad de Lisboa; PortugalFil: Nieuwendam, Alexandre. Universidad de Lisboa; PortugalFil: Ferreira, Alice. Universidad de Lisboa; PortugalFil: Oliva, Marc. Universidad de Lisboa; Portuga

Using models of the Earth's atmosphere to assess exoplanet habitability

Recent advances in telescope technology have allowed us to detect planets and bodies that have the potential to be habitable. Habitability can be defined in a number of ways, but most commonly it is defined by the availability of liquid water. There are a vast number of factors that determine whether or not liquid water is present in an atmosphere or on a surface, and due to the limited observational data, our understanding of the role of each of these factors is poor, especially as we move further through the parameter space away from the Earth. Until data from the next generation of telescopes are available, attempts to constrain atmospheric habitability have to utilise computer modelling. Modelling has a long history in habitability studies, particularly with regards to the inner and outer boundaries of the circumstellar habitable zone (CHZ). Early models were 1-dimensional (1D), but in the last decade the balance has shifted towards 3-dimensional (3D) global circulation models (GCMs) that describe the air flow in a planetary atmosphere in a much more sophisticated way. In part this was due to the recognition of the importance of 3D processes like clouds and convection in the global energy balance, and in part due to the increasing prioritisation of planets that are dissimilar to Earth, such as M-dwarf planets, which show features such as tidal-locking and atmospheric jets that result in less spatial uniformity through the atmosphere, limiting the applicability of 1D models. As of this writing our current best hopes for habitability are M-dwarf planets such as the TRAPPIST planets and Proxima Centauri b that orbit in the habitable zone, with rocky compositions. M-dwarf planets were previously overlooked as candidate habitable planets in favour of G-star planets like the Earth. However, some researchers now favour M-dwarfs in light of modern GCM results, observational biases and planetary population statistics, demonstrating that we must be careful not to define habitability in a way that is too Earth-centric. In this thesis we expand on knowledge of habitability through models that are informed by Earth science, but that do not necessarily describe Earth-like environments. In Chapter 2, we consider an environment that has not been studied through the lens of habitability before: ultra-cool Y dwarf atmospheres. In the atmospheres of these bodies it is thought that there may be liquid water clouds and temperatures and pressures similar to those on the Earth's surface. However, as there is no surface it is important that any potential organisms are able to remain above the hot lower atmosphere and the cold upper atmosphere; we compare with the Earth's atmosphere, where microbes are able to stay in the atmosphere for weeks, even metabolising in clouds. We study this environment through a simple radiative or convective atmosphere paired with a model informed by nutrient-phytoplankton-zooplankton models from the Earth's ocean. We find that organisms similar in size to microbes can remain aloft in this environment due to upward convective winds. In Chapter 3, contrasting with the simple approach in the previous chapter, we describe the development of a highly-sophisticated, fully online, 3D photochemical model of an exoplanet atmosphere. We apply this model to a tidally-locked M-dwarf aqua planet with an Earth-like atmosphere, nominally Proxima Centauri b, to evaluate the impacts of the differing stellar energy spectrum and dramatically different global circulation on an ozone layer described through the Chapman mechanism and the hydrogen oxide catalytic cycle. We find that the ozone layer is unlike that seen in the Earth's atmosphere. The lack of UV photons from our quiescent M-dwarf results in very long chemical lifetimes, which means that the atmospheric transport becomes the dominant factor in the structure of the ozone layer. We see an accumulation of ozone in the night-side cold traps (or gyres) at low altitudes where transport is slow and lifetimes are long, resulting in a dramatic day-night contrast in ozone columns. Total ozone column is much smaller on an M-dwarf planet compared with the Earth, by around a factor of 10, owing to top-of-atmosphere UV flux. In Chapter 4, we develop on the results of Chapter 3 by altering certain parameters in the model and examining the effect on the climate. We find that dramatic changes occur when switching off the chemistry scheme and reverting to a prescribed Earth ozone layer. Specifically we find that the temperatures on the night side of the planet change by more than 50 K, accompanied by dramatic changes in the pole temperatures. In addition the cold traps move towards the equator and eastwards. These changes are caused by the smaller ozone columns that result from the interactive chemistry, which severely reduce night side atmosphere opacity. This opacity controls the night side cooling rate which in turn controls the atmospheric circulation through the day-tonight temperature contrast. We find that similar effects occur when switching off the hydrogen oxide catalytic loss cycle, though to a lesser extent. Furthermore, we examine the effects of electromagnetic flares on the chemistry, which do not seem to impact ozone columns, in agreement with previous works. Finally we demonstrate the changes in atmospheric ozone and climate in a 3:2 resonant orbit and with an Earth-like orbit and top-of-atmosphere flux. In sum, our results with this model show that the climate is highly sensitive to the ozone columns, and demonstrate the importance of fully-coupled 3D photochemical models, which have been used very rarely in exoplanet atmosphere modelling

Biodiversity of cryopegs in permafrost

Abstract This study describes the biodiversity of the indigenous microbial community in the sodium-chloride water brines (cryopegs) derived from ancient marine sediments and sandwiched within permafrost 100-120,000 years ago after the Arctic Ocean regression. Cryopegs remain liquid at the in situ temperature of À9 to À11°C and make up the only habitat on the Earth that is characterized by permanently subzero temperatures, high salinity, and the absence of external influence during geological time. From these cryopegs, anaerobic and aerobic, spore-less and spore-forming, halotolerant and halophilic, psychrophilic and psychrotrophic bacteria, mycelial fungi and yeast were isolated and their activity was detected below 0°C

Resistance of Antarctic black fungi and cryptoendolithic communities to simulated space and Martian conditions

Dried colonies of the Antarctic rock-inhabiting meristematic fungi Cryomyces antarcticus CCFEE 515, CCFEE 534 and C. minteri CCFEE 5187, as well as fragments of rocks colonized by the Antarctic cryptoendolithic community, were exposed to a set of ground-based experiment verification tests (EVTs) at the German Aerospace Center (DLR, Köln, Germany). These were carried out to test the tolerance of these organisms in view of their possible exposure to space conditions outside of the International Space Station (ISS). Tests included single or combined simulated space and Martian conditions. Responses were analysed both by cultural and microscopic methods. Thereby, colony formation capacities were measured and the cellular viability was assessed using live/dead dyes FUN 1 and SYTOX Green. The results clearly suggest a general good resistance of all the samples investigated. C. minteri CCFEE 5187, C. antarcticus CCFEE 515 and colonized rocks were selected as suitable candidates to withstand space flight and long-term permanence in space on the ISS in the framework of the LIchens and Fungi Experiments (LIFE programme, European Space Agency)

Proteomic analysis of cold adaptation in a Siberian permafrost bacterium – Exiguobacterium sibiricum 255–15 by two-dimensional liquid separation coupled with mass spectrometry

Bacterial cold adaptation in Exiguobacterium sibiricum 255–15 was studied on a proteomic scale using a 2-D liquid phase separation coupled with MS technology. Whole-cell lysates of E. sibiricum 255–15 grown at 4°C and 25°C were first fractionated according to p I by chromatofocusing (CF), and further separated based on hydrophobicity by nonporous silica RP HPLC (NPS-RP-HPLC) which was on-line coupled with an ESI-TOF MS for intact protein M r measurement and quantitative interlysate comparison. Mass maps were created to visualize the differences in protein expression between different growth temperatures. The differentially expressed proteins were then identified by PMF using a MALDI-TOF MS and peptide sequencing by MS/MS with a MALDI quadrupole IT TOF mass spectrometer (MALDI-QIT-TOF MS). A total of over 500 proteins were detected in this study, of which 256 were identified. Among these proteins 39 were cold acclimation proteins (Caps) that were preferentially or uniquely expressed at 4°C and three were homologous cold shock proteins (Csps). The homologous Csps were found to be similarly expressed at 4°C and 25°C, where these three homologous Csps represent about 10% of the total soluble proteins at both 4°C and 25°C.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/55850/1/5221_ftp.pd

Ice wedges as archives of winter palaeoclimate: a review

Ice wedges are a characteristic feature of northern permafrost landscapes and grow mainly by snowmelt that refreezes in thermal contraction cracks that open in winter. In high latitudes the stable‐isotope composition of precipitation (δ18O and δD) is sensitive to air temperature. Hence, the integrated climate information of winter precipitation is transferred to individual ice veins and can be preserved over millennia, allowing ice wedges to be used to reconstruct past winter climate. Recent studies indicate a promising potential of ice‐wedge‐based paleoclimate reconstructions for more comprehensive reconstructions of Arctic past climate evolution. We briefly highlight the potential and review the current state of ice‐wedge paleoclimatology. Existing knowledge gaps and challenges are outlined and priorities for future ice‐wedge research are suggested. The major research topics are (1) frost cracking and infilling dynamics, (2) formation and preservation of the stable‐isotope information, (3) ice‐wedge dating, (4) age‐model development and (5) interpretation of stable‐isotope time series. Progress in each of these topics will help to exploit the paleoclimatic potential of ice wedges, particularly in view of their unique cold‐season information, which is not adequately covered by other terrestrial climate archives

Régimen térmico y variabilidad espacial de la capa activa en Isla Decepcion, Antártida

El programa de monitoreo de capa activa (CALM) fue desarrollado en las últimas décadas con la finalidad de comprender el impacto del cambio climático sobre los ambientes con permafrost. Este trabajo analiza los resultados obtenidos, en los últimos seis años, de los sitios CALM-S Irizar, Cráter Lake y Refugio Chileno, ubicados en Isla Decepción. En ellos se ha medido el espesor, el estado térmico y la distribución espacial de la capa activa. En los sitios Irizar y Refugio Chileno la evolución del espesor de capa activa varió interanualmente sin una clara tendencia dentro del corto período analizado; por el contrario, el sitio Cráter Lake evidenció una tendencia a la disminución de espesor. La distribución espacial como el espesor de dicha capa en los tres sitios de monitoreo, mostraron estar condicionados principalmente por la potencia de la cubierta de nieve, la litología y la exposición a los vientos. El relieve, la topografía de detalle, la orientación de las laderas frente a la radiación solar incidente, ejercieron un control menor sobre esta distribución. El estado térmico de la capa activa evidenció el control ejercido sobre ella de la temperatura del aire y de la cubierta nival. Así bajo reducidos espesores de nieve, el modelo de penetración en profundidad de la isoterma de 0 ºC, ha permitido aproximar satisfactoriamente el espesor de capa activa.Thermal regime and spatial variability of the active layer in Deception Island, Antarctica The Circumpolar Active Layer Monitoring (CALM) program developed over the last two decades has a leading edge in comprehensive efforts to study the impacts of climate change in permafrost environments. This paper describes results obtained during the last six years, on the active layer thickness, thermal regime and spatial patterns of thaw, at the CALM-S Irizar, Crater Lake and Refugio Chileno sites in Deception Island. In Irizar and Refugio Chileno CALM-S sites the active layer depth varied interannually without any clear trend over the short record available. By contrast, Crater Lake CALM-S showed a slight thinning trend. In all sites, the spatial patterns of thaw and active layer thickness were mainly controlled by snow cover conditions, lithology and the effect of aspect on wind. The relief, the detailed topography and the effect of aspect on solar radiation also exert a local control over its patterns. Air temperature and snow cover controlled the thermal state of active layer. In absence of snow, the use of depth penetration model of the 0 ºC isotherm allowed approximated satisfactorily active layer thickness.info:eu-repo/semantics/publishedVersio