PARASO, a circum-Antarctic fully coupled ice-sheet–ocean–sea-ice–atmosphere–land model involving f.ETISh1.7, NEMO3.6, LIM3.6, COSMO5.0 and CLM4.5

We introduce PARASO, a novel five-component fully coupled regional climate model over an Antarctic circumpolar domain covering the full Southern Ocean. The state-of-the-art models used are the fast Elementary Thermomechanical Ice Sheet model (f.ETISh) v1.7 (ice sheet), the Nucleus for European Modelling of the Ocean (NEMO) v3.6 (ocean), the Louvain-la-Neuve sea-ice model (LIM) v3.6 (sea ice), the COnsortium for Small-scale MOdeling (COSMO) model v5.0 (atmosphere) and its CLimate Mode (CLM) v4.5 (land), which are here run at a horizontal resolution close to . One key feature of this tool resides in a novel two-way coupling interface for representing ocean–ice-sheet interactions, through explicitly resolved ice-shelf cavities. The impact of atmospheric processes on the Antarctic ice sheet is also conveyed through computed COSMO-CLM–f.ETISh surface mass exchange. In this technical paper, we briefly introduce each model's configuration and document the developments that were carried out in order to establish PARASO. The new offline-based NEMO–f.ETISh coupling interface is thoroughly described. Our developments also include a new surface tiling approach to combine open-ocean and sea-ice-covered cells within COSMO, which was required to make this model relevant in the context of coupled simulations in polar regions. We present results from a 2000–2001 coupled 2-year experiment. PARASO is numerically stable and fully operational. The 2-year simulation conducted without fine tuning of the model reproduced the main expected features, although remaining systematic biases provide perspectives for further adjustment and development

Backflow and density excitations in quantum fluids

By the use of the f sum rule and a separation of density excitations into single and multiple excitations, we derive exact quantum expressions for the backflow contribution to the dynamic structure function S ( k , Ω) and for the discrete single-excitation spectrum Ω k . The derivation is carried out for Bose liquids, Fermi liquids, charged quantum liquids, quantum solutions, an impurity atom dissolved in quantum fluids, and phonons in solids. It is shown that the backflow arises from virtual multiexcitations and that real multiexcitations give rise to a background. It is argued that multiexcitations are relatively insensitive to long-range order or quantum statistics. Thus the backflow and background contributions to S ( k , Ω) of the liquid and solid phases of 4 He, and also that to S ( k ) of liquid 3 He and of liquid 4 He, are expected to be similar, which is consistent with existing data. The exact expression for Ω k , which shows that multiexcitations effectively repel the single excitations, is used to make some speculations concerning the large-wavevector phonon spectrum in liquid 3 He and in 3 He- 4 He solutions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44954/1/10909_2004_Article_BF00116969.pd