The mid-late Miocene is an important interval in the evolution of global climate through the Cenozoic, representing a key period in the transition out of the warm, dynamic climate state of the Miocene Climatic Optimum (MCO) into a more stable unipolar icehouse world (Badger et al., 2013; Foster et al., 2012; Greenop et al., 2014; Sosdian et al., 2018). Despite being characterized by similar to modern day atmospheric CO 2 concentrations (Foster et al., 2012; Sosdian et al., 2018; Super et al., 2018), middle Miocene mean global temperatures were likely significantly warmer than the modern day (Pound et al., 2011; Rousselle et al., 2013). This has been used to suggest a decoupling of global temperature and atmospheric CO 2 forcing (LaRiviere et al., 2012; Pagani et al., 1999), a characteristic which general circulation models struggle to simulate (Knorr et al., 2011; von der Heydt & Dijkstra, 2006). It has also been suggested that the late Miocene was an additional important key step in the transition to our modern climate state, as high latitudes cooled more than low latitudes, leading to a marked steepening of latitudinal temperature gradients (Herbert et al., 2016). The late Miocene Cooling (LMC) between ∼ 7.5 and 5.5 Ma was a global phenomenon (Herbert et al., 2016) perhaps associated with decreasing atmospheric pCO 2 (Stoll et al., 2019). The increase in the equator to pole surface temperature gradients was not associated with an increase in the benthic foraminiferal oxygen isotope record, implying that it occurred in the absence of a large increase in continental ice volume (Herbert et al., 2016). Polar amplification in the LMC is consistent with estimates for other time intervals (e.g., Cramwinckel et al., 2018). However, the LMC was also preceded by a significant cooling of mid to high southern and northern latitudes, a heterogenous cooling at high northern latitudes, and a muted, limited cooling in the tropics (Herbert et al., 2016). This heterogenous cooling perhaps suggests an unusually high polar amplification factor for the interval immediately preceding the LMC. Potential changes in the Earth System that could impact the magnitude of polar amplification include sea ice extent, vegetation induced changes in albedo, cloud cover, or ocean-atmosphere heat transport. Constraining the magnitude and timing of the

The Arctic Ocean region is currently undergoing dramatic changes, which will likely alter the nutrient cycles that underpin Arctic marine ecosystems. Phosphate is a key limiting nutrient for marine life but gaps in our understanding of the Arctic phosphorus (P) cycle persist. In this study, we investigate the benthic burial and recycling of phosphorus using sediments and pore waters from the Eurasian Arctic margin, including the Barents Sea slope and the Yermak Plateau. Our results highlight that P is generally lost from sediments with depth during organic matter respiration. On the Yermak Plateau, remobilization of P results in a diffusive flux of P to the seafloor of between 96 and 261 µmol m −2  yr −1 . On the Barents Sea slope, diffusive fluxes of P are much larger (1736–2449 µmol m −2  yr −1 ), but these fluxes are into near-surface sediments rather than to the bottom waters. The difference in cycling on the Barents Sea slope is controlled by higher fluxes of fresh organic matter and active iron cycling. As changes in primary productivity, ocean circulation and glacial melt continue, benthic P cycling is likely to be altered with implications for P imported into the Arctic Ocean Basin. This article is part of the theme issue ‘The changing Arctic Ocean: consequences for biological communities, biogeochemical processes and ecosystem functioning’.

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The mid-late Miocene is an important interval in the evolution of global climate through the Cenozoic, representing a key period in the transition out of the warm, dynamic climate state of the Miocene Climatic Optimum (MCO) into a more stable unipolar icehouse world (Badger et al., 2013;Foster et al., 2012;Greenop et al., 2014;Sosdian et al., 2018). Despite being characterized by similar to modern day atmospheric CO 2 concentrations (Foster et al., 2012;Sosdian et al., 2018;Super et al., 2018), middle Miocene mean global temperatures were likely significantly warmer than the modern day (Pound et al., 2011;Rousselle et al., 2013). This has been used to suggest a decoupling of global temperature and atmospheric CO 2 forcing (LaRiviere et al., 2012;Pagani et al., 1999), a characteristic which general circulation models struggle to simulate (Knorr et al., 2011;von der Heydt & Dijkstra, 2006). It has also been suggested that the late Miocene was an additional important key step in the transition to our modern climate state, as high latitudes cooled more than low latitudes, leading to a marked steepening of latitudinal temperature gradients (Herbert et al., 2016).The late Miocene Cooling (LMC) between ∼ 7.5 and 5.5 Ma was a global phenomenon (Herbert et al., 2016) perhaps associated with decreasing atmospheric pCO 2 (Stoll et al., 2019). The increase in the equator to pole surface temperature gradients was not associated with an increase in the benthic foraminiferal oxygen isotope record, implying that it occurred in the absence of a large increase in continental ice volume (Herbert et al., 2016). Polar amplification in the LMC is consistent with estimates for other time intervals (e.g., Cramwinckel et al., 2018). However, the LMC was also preceded by a significant cooling of mid to high southern and northern latitudes, a heterogenous cooling at high northern latitudes, and a muted, limited cooling in the tropics (Herbert et al., 2016). This heterogenous cooling perhaps suggests an unusually high polar amplification factor for the interval immediately preceding the LMC. Potential changes in the Earth System that could impact the magnitude of polar amplification include sea ice extent, vegetation induced changes in albedo, cloud cover, or ocean-atmosphere heat transport. Constraining the magnitude and timing of the