Coupling framework (1.0) for the PISM (1.1.4) ice sheet model and the MOM5 (5.1.0) ocean model via the PICO ice shelf cavity model in an Antarctic domain

The past and future evolution of the Antarctic Ice Sheet is largely controlled by interactions between the ocean and floating ice shelves. To investigate these interactions, coupled ocean and ice sheet model configurations are required. Previous modelling studies have mostly relied on high-resolution configurations, limiting these studies to individual glaciers or regions over short timescales of decades to a few centuries. We present a framework to couple the dynamic ice sheet model PISM (Parallel Ice Sheet Model) with the global ocean general circulation model MOM5 (Modular Ocean Model) via the ice shelf cavity model PICO (Potsdam Ice-shelf Cavity mOdel). As ice shelf cavities are not resolved by MOM5 but are parameterized with the PICO box model, the framework allows the ice sheet and ocean components to be run at resolutions of 16 km and 3∘ respectively. This approach makes the coupled configuration a useful tool for the analysis of interactions between the Antarctic Ice Sheet and the global ocean over time spans of the order of centuries to millennia. In this study, we describe the technical implementation of this coupling framework: sub-shelf melting in the ice sheet component is calculated by PICO from modelled ocean temperatures and salinities at the depth of the continental shelf, and, vice versa, the resulting mass and energy fluxes from melting at the ice–ocean interface are transferred to the ocean component. Mass and energy fluxes are shown to be conserved to machine precision across the considered component domains. The implementation is computationally efficient as it introduces only minimal overhead. Furthermore, the coupled model is evaluated in a 4000 year simulation under constant present-day climate forcing and is found to be stable with respect to the ocean and ice sheet spin-up states. The framework deals with heterogeneous spatial grid geometries, varying grid resolutions, and timescales between the ice and ocean component in a generic way; thus, it can be adopted to a wide range of model set-ups

CM2Mc-LPJmL v1.0: biophysical coupling of a process-based dynamic vegetation model with managed land to a general circulation model

The terrestrial biosphere is exposed to land-use and climate change, which not only affects vegetation dynamics but also changes land–atmosphere feedbacks. Specifically, changes in land cover affect biophysical feedbacks of water and energy, thereby contributing to climate change. In this study, we couple the well-established and comprehensively validated dynamic global vegetation model LPJmL5 (Lund–Potsdam–Jena managed Land) to the coupled climate model CM2Mc, the latter of which is based on the atmosphere model AM2 and the ocean model MOM5 (Modular Ocean Model 5), and name it CM2Mc-LPJmL. In CM2Mc, we replace the simple land-surface model LaD (Land Dynamics; where vegetation is static and prescribed) with LPJmL5, and we fully couple the water and energy cycles using the Geophysical Fluid Dynamics Laboratory (GFDL) Flexible Modeling System (FMS). Several improvements to LPJmL5 were implemented to allow a fully functional biophysical coupling. These include a sub-daily cycle for calculating energy and water fluxes, conductance of the soil evaporation and plant interception, canopy-layer humidity, and the surface energy balance in order to calculate the surface and canopy-layer temperature within LPJmL5. Exchanging LaD with LPJmL5 and, therefore, switching from a static and prescribed vegetation to a dynamic vegetation allows us to model important biospheric processes, including fire, mortality, permafrost, hydrological cycling and the impacts of managed land (crop growth and irrigation). Our results show that CM2Mc-LPJmL has similar temperature and precipitation biases to the original CM2Mc model with LaD. The performance of LPJmL5 in the coupled system compared to Earth observation data and to LPJmL offline simulation results is within acceptable error margins. The historical global mean temperature evolution of our model setup is within the range of CMIP5 (Coupled Model Intercomparison Project Phase 5) models. The comparison of model runs with and without land-use change shows a partially warmer and drier climate state across the global land surface. CM2Mc-LPJmL opens new opportunities to investigate important biophysical vegetation–climate feedbacks with a state-of-the-art and process-based dynamic vegetation model

De eiwitstoffen der glandula thymus

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Quantifying Southern Annular Mode paleo-reconstruction skill in a model framework

Past attempts to reconstruct the Southern Annular Mode (SAM) using paleo-archives have resulted in records which can differ significantly from one another prior to the window over which the proxies are calibrated. This study attempts to quantify not only the skill with which we may expect to reconstruct the SAM but also to assess the contribution of regional bias in proxy selection and the impact of non-stationary proxy–SAM teleconnections on a resulting reconstruction. This is achieved using a pseudoproxy framework with output from the GFDL CM2.1 global climate model. Reconstructions derived from precipitation fields perform better, with 89 % of the reconstructions calibrated over a 61 year window able to reproduce at least 50 % of the inter-annual variance in the SAM, as opposed to just 25 % for surface air temperature (SAT)-derived reconstructions. Non-stationarity of proxy–SAM teleconnections, as defined here, plays a small role in reconstructions, but the range in reconstruction skill is not negligible. Reconstructions are most likely to be skilful when proxies are sourced from a geographically broad region with a network size of at least 70 proxies

Reconstructing the Southern Hemisphere Westerlies and their role in changing atmospheric CO2

This thesis investigates the impact of changing Southern Hemisphere westerly winds (SHW) on the ocean carbon cycle and our ability to robustly reconstruct these wind changes over the past millennium using paleo-proxy data. Transient and equilibrated impacts of changes in SHW wind stress on ocean circulation and carbon pumps are explored using a fully coupled Earth system climate model of intermediate complexity (UVic) while our ability to reconstruct the winds, interpreted as changes in the Southern Annular Mode (SAM), is assessed in both a pseudo-proxy (GFDL CM2.1) and a physical paleo-proxy framework. The main findings of this thesis are: (i) A southward shift of the SHW during the deglaciation in conjunction with changes in Atlantic overturning, provide a plausible mechanism for ventilation of the deep ocean and may explain recorded changes in atmospheric CO2 and Δ14 C. (ii) Small perturbations of the latitudinal position and intensity of the SHW in isolation of other forcing has the potential to significantly alter air-sea carbon exchange, caused primarily by circulation-driven changes in the physical and biological pumps. (iii) Our ability to identify such changes in the winds is limited, as reconstructions in a model framework suggest that only approximately 50% of SAM variance is captured. Maximising the size of the proxy network, calibration window length and geographic diversity of proxy source regions are all shown to aid in producing a more skilful reconstruction. (iv) Paleo-reconstructions of SAM differ significantly due to the nature of the proxy network and the index with which it is calibrated, while the reconstruction method used is less important. Despite significant differences, all reconstructed indices share significant low frequency variability in the 64-128 year space. Overall, while the model simulations suggest that changing SHW may contribute significantly to observed changes in CO2 on multi-decadal to centennial time-scales, our inability to reconstruct the winds robustly currently precludes us from making such connections

Pulsed power technology

\u3cp\u3ePulsed power refers to the science and technology of accumulating energy over a relatively long period of time and releasing it as a high-power pulse composed of high voltage and current over a short period of time; as such, it has extremely high power but moderately low energy. Pulsed power is produced by transferring energy generally stored in capacitors and inductors to a load very quickly through switching devices. Applications of pulsed power continue expan sion into fields including the environment, recycling, energy, defense, material processing, medical treatment, plasma medicine, and food and agriculture. Building upon the development of pulsed power generators which offer both high repetition and performance, scientists are now able to investigate effects of pulsed power on living organisms, and their research has expanded to encompass a new field known as bioelectrics. Section 2.1 summarizes pulsed power technology with a focus on this new field. Section 2.2 summarizes the basics of electric circuits, while Sect. 2.3 discusses pulsed power generators utilized for bioelectrics. Section 2.4 describes switches as a key technology. Measurement tools of pulsed power are shown in Sect. 2.5, and delivery of electric pulses to biological tissues using antennas is described in Sect. 2.6.\u3c/p\u3

Hyperstratification following glacial overturning events in the northern Arabian Sea

[1] Correlations between Arabian Sea organic carbon and GISP2 d18O records indicate a pronounced oxygen minimum zone (OMZ) during interstadials, whereas well-oxygenated conditions prevailed during stadials. Local deep winter mixing ventilated intermediate water during the coldest stadials, corresponding to North Atlantic Heinrich events. Here we show that in the Arabian Sea periods of climatic warming following Heinrich events H6–H4 and the Younger Dryas (YD) are characterized by dominant Polysphaeridium zoharyi (dinoflagellate) cysts. The finding of assemblages dominated by P. zoharyi in the open ocean is unusual because today similar assemblages are restricted to lagoonal settings. It is postulated that the highly saline mixed layer and the strong density gradient which characterized Arabian Sea hydrography after H6–H4 and the YD simulated a shallow seafloor, thereby enabling germination of cysts prior to sinking. The strong density gradient following cold stadials should have facilitated the rapid reestablishment of a pronounced OMZ during interstadials

Earth beyond six of nine planetary boundaries

This planetary boundaries framework update finds that six of the nine boundaries are transgressed, suggesting that Earth is now well outside of the safe operating space for humanity. Ocean acidification is close to being breached, while aerosol loading regionally exceeds the boundary. Stratospheric ozone levels have slightly recovered. The transgression level has increased for all boundaries earlier identified as overstepped. As primary production drives Earth system biosphere functions, human appropriation of net primary production is proposed as a control variable for functional biosphere integrity. This boundary is also transgressed. Earth system modeling of different levels of the transgression of the climate and land system change boundaries illustrates that these anthropogenic impacts on Earth system must be considered in a systemic context