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<p>The Miocene Climatic Optimum (MCO, ~17-15 Ma) was a relatively warm interval that interrupted the Cenozoic cooling trend and bears analogies with projected <em>end-of-the-century</em> climate. Proxy data and model simulations indicate temperatures were on average ~7 – 8°C higher than present day and atmospheric <em>p</em>CO<sub>2</sub> values were 500-600 ppmV. At high latitudes, upper ocean temperatures were ~10 – 15°C warmer than present day, but available tropical temperature records are limited. Importantly, to be able to use Miocene paleoclimate records to quantify key climate parameters like the polar amplification of climate change, accurate reconstructions of tropical surface oceans are required.</p><p>We present high resolution Early to Middle Miocene (~15 – 18 Ma) records of tropical sea surface temperature (SST) variability based on the lipid biomarker paleothermometer TEX<sub>86</sub> at Ocean Drilling Program (ODP) Site 959 in the eastern equatorial Atlantic Ocean and at ODP Site 1007 at Bahama Bank in the western tropical Atlantic Ocean. The age model for both sites is based on chemo- and biostratigraphy. Moreover, analyses of bulk carbonate oxygen- (δ<sup>1</sup><sup>8</sup>O) and stable carbon (δ<sup>13</sup>C) isotope ratios at ~2 – 4 kyr resolution at Site 959 facilitated orbital tuning to eccentricity, obliquity and precession. Bulk elemental composition records, total organic carbon concentrations and dinoflagellate cyst assemblages were also generated to assess paleoenvironmental change.</p><p>At both sites, warming associated with the onset of the MCO (~17 Ma) was identified as an average SST increase of ~2°C (using the TEX<sub>86</sub>-H calibration). At ~16.8 Ma, bulk carbonate δ<sup>13</sup>C gradually increased by ~1‰ at both sites, indicating the onset of the Monterey carbon isotope excursion. Combined with available temperature information from the high latitudes and deep ocean, we assess meridional temperature gradients across the MCO.</p><p>At ODP Site 959, sediments are characterized by alternations of biogenic silica, carbonates, and terrigenous material (i.e., clays). Following the onset of the MCO (~17 – 16.5 Ma), high variability in the oceanographical setting is reflected in striking Ba<sub>bio</sub> peaks, indicating productivity changes. These peaks coincide with lowest SSTs (~28°C) and increased dust supply (increased Fe and Ti) on precession and obliquity timescales. In the same interval, (inner-) neritic dinoflagellate species indicate increased water column stratification. Heterotrophic dinocyst groups vary on timescales coherent with the other geochemical records, relative to comparably stable background abundances of oceanic genera throughout the MCO. Combined, this suggests that a highly dynamic monsoon-driven upwelling regime was present at Site 959 during the MCO. Combined, these patterns imply a highly dynamic African monsoon-driven upwelling regime that intensified at the onset of the MCO.</p>

<p>The linearised DC loadflow is a fast way to calculate the load flow. However, until now changes in topology due to busbar splitting cannot be dealt with in an efficient way. In this study, we introduce the Bus Split Distribution Factors (BSDF) which enable an efficient way to compute the effects of busbar splitting on the DC load flow. The derivation of the BSDF formulas is based on modelling the busbar coupler as a branch with vanishing reactance and by using transformed LODF formulas. In times of the energy transition the BSDF approch might be especially helpful since optimal grid topology control is still a largely unexploited form of flexibility for system operators due to the complex combinatorial nature of grid topology reconfiguration. With the BSDF approach much faster screening of topological remedial actions (including substation reconfigurations) in congestion management applications is possible. </p>

<p>The linearised DC loadflow is a fast way to calculate the load flow. However, until now changes in topology due to busbar splitting cannot be dealt with in an efficient way. In this study, we introduce the Bus Split Distribution Factors (BSDF) which enable an efficient way to compute the effects of busbar splitting on the DC load flow. The derivation of the BSDF formulas is based on modelling the busbar coupler as a branch with vanishing reactance and by using transformed LODF formulas. In times of the energy transition the BSDF approch might be especially helpful since optimal grid topology control is still a largely unexploited form of flexibility for system operators due to the complex combinatorial nature of grid topology reconfiguration. With the BSDF approach much faster screening of topological remedial actions (including substation reconfigurations) in congestion management applications is possible. </p>