A preparation technique is described in which a layer of TiOz completely covering the support can be deposited onto silica. Onto the support thus modified, V,05 can be applied to result in a catalyst suitable for the selective catalytic reduction (SCR) of NO, with NH3. To ohtain the required selectivity in the reduction of NO, the silica surface must be completely covered with TiOz. Catalysts prepared according to the above procedure exhibit good activity and a completely selective reduction of NO to Nz at temperatures to 350°C. At higher temperatures selective oxidation of the NH3 to Nz is observed. 0 1988 Academic press, IK.

ChemInform Abstract A preparation technique is described that allows the replacement of the bulk TiO2 in V2O5/TiO2 catalysts by silica and leads to low-cost catalysts which are highly active, selective, and resistant to SO2. In order to obtain high selectivity in the reduction of NOx with NH3, the silica surface must be completely covered with TiO2 (20-25 wt.% TiO2 loading).

Abstract. Maud Rise polynyas (MRPs) form due to deep convection, which is caused by static instabilities of the water column. Recent studies with the Community Earth System Model (CESM) have indicated that a multidecadal varying heat accumulation in the subsurface layer occurs prior to MRP formation due to the heat transport over the Weddell Gyre. In this study, a conceptual MRP box model, forced with CESM data, is used to investigate the role of this subsurface heat accumulation in MRP formation. Cases excluding and including multidecadal varying subsurface heat and salt fluxes are considered, and multiple polynya events are only simulated in the cases where subsurface fluxes are included. The dominant frequency for MRP events in these results, approximately the frequency of the subsurface heat and salt accumulation, is still visible in cases where white noise is added to the freshwater flux. This indicates the importance and dominance of the subsurface heat accumulation in MRP formation.

Marine carbon cycle processes are important for taking up atmospheric CO2 thereby reducing climate change. Net primary and export production are important pathways of carbon from the surface to the deep ocean where it is stored for millennia. Climate change can interact with marine ecosystems via changes in the ocean stratification and ocean circulation. In this study we use results from the Community Earth System Model version 2 (CESM2) to assess the effect of a changing climate on biological production and phytoplankton composition in the high latitude North Atlantic Ocean. We find a shift in phytoplankton type dominance from diatoms to small phytoplankton which reduces net primary and export productivity. Using a conceptual carbon‐cycle model forced with CESM2 results, we give a rough estimate of a positive phytoplankton composition‐atmospheric CO2 feedback of approximately 60 GtCO2/°C warming in the North Atlantic which lowers the 1.5° and 2.0°C warming safe carbon budgets.

To avoid crossing tipping points in the Earth system, it is important to keep warming of our planet to a maximum of 1.5-2°C (Lenton et al., 2019). Policymakers need to know how much carbon we can still emit before we exceed this warming. However, estimates of this safe carbon budget are difficult and subject to large uncertainties because the Earth system has many processes and feedbacks that are not completely understood yet (Matthews et al., 2021).The marine carbon pumps are currently responsible for taking up 25%-40% of anthropogenic carbon (DeVries et al., 2017;Sabine et al., 2004). It is estimated that the biological carbon pump exports approximately 11 GtC yr −1 to the deep ocean (Sanders et al., 2014) and that without this export, atmospheric pCO 2 values would be 200-400 ppm higher (Henson et al., 2022;Ito & Follows, 2005). This export production (EP) is dependent on the net primary productivity (NPP). It also depends on food web dynamics and plankton composition, since different phyto-and zooplankton species have different remineralization depths (