The history of the Arctic Ocean during the Cenozoic era (0-65 million years ago) is largely unknown from direct evidence. Here we present a Cenozoic palaeoceanographic record constructed from >400 m of sediment core from a recent drilling expedition to the Lomonosov ridge in the Arctic Ocean. Our record shows a palaeoenvironmental transition from a warm 'greenhouse' world, during the late Palaeocene and early Eocene epochs, to a colder 'icehouse' world influenced by sea ice and icebergs from the middle Eocene epoch to the present. For the most recent ∼14 Myr, we find sedimentation rates of 1-2 cm per thousand years, in stark contrast to the substantially lower rates proposed in earlier studies; this record of the Neogene reveals cooling of the Arctic that was synchronous with the expansion of Greenland ice (∼3.2 Myr ago) and East Antarctic ice (∼14 Myr ago). We find evidence for the first occurrence of ice-rafted debris in the middle Eocene epoch (∼45 Myr ago), some 35 Myr earlier than previously thought; fresh surface waters were present at ∼49 Myr ago, before the onset of ice-rafted debris. Also, the temperatures of surface waters during the Palaeocene/Eocene thermal maximum (∼55 Myr ago) appear to have been substantially warmer than previously estimated. The revised timing of the earliest Arctic cooling events coincides with those from Antarctica, supporting arguments for bipolar symmetry in climate change. © 2006 Nature Publishing Group

Sixteen deep‐sea cores from the central equatorial Pacific are used to reconstruct a continuous 800,000‐year (800‐kyr) record of bathymetric variations in carbonate preservation as measured by calcium carbonate (CaCO3) content. The depth of the sedimentary lysocline has fluctuated markedly in conjunction with late Pleistocene climate cycles while the carbonate critical depth (CCrD), which is the water depth where the sediments contain 10% CaCO3, has remained relatively constant. As a result, the depth of the lysocline controls the bathymetric position and thickness of the CaCO3 transition zone, defined as the depth from the lysocline to the CCrD. Modern and interglacial‐aged sediments show poor CaCO3 preservation and thick CaCO3 transition zones. Glacial‐aged sediments show good preservation and deep, thin zones due to the deepening of the lysocline. Detailed comparison of the CaCO3 preservation and oxygen isotope records from the central equatorial Pacific confirms the observation that preservation maxima and minima tend to occur during the latter half of glacial and interglacial stages and on climate transitions rather than during the middle of climatic stages. During the nine major glacial stages of the last 800 kyr, the lysocline deepened by at least 400 to 800 m. This deepening indicates an increase in the abyssal carbonate ion concentration ([CO3=]) and a depression of the calcite saturation horizon best explained by the deeper presence of a more carbonate‐saturated water mass. The bottom of the transition zone has remained at a relatively constant depth during the Brunhes Chron, indicating a balance between CaCO3 sedimentation and dissolution in the deepest waters of the central equatorial Pacific.

The assessment of competitive movement demands in team sports has traditionally relied upon global positioning system (GPS) analyses presented as fixed-time epochs (e.g., 5–40 min). More recently, presenting game data as a rolling average has become prevalent due to concerns over a loss of sampling resolution associated with the windowing of data over fixed periods. Accordingly, this study compared rolling average (ROLL) and fixed-time (FIXED) epochs for quantifying the peak movement demands of international rugby union match-play as a function of playing position. Elite players from three different squads (n = 119) were monitored using 10 Hz GPS during 36 matches played in the 2014–2017 seasons. Players categorised broadly as forwards and backs, and then by positional sub-group (FR: front row, SR: second row, BR: back row, HB: half back, MF: midfield, B3: back three) were monitored during match-play for peak values of high-speed running (>5 m·s-1; HSR) and relative distance covered (m·min-1) over 60–300 s using two types of sample-epoch (ROLL, FIXED). Irrespective of the method used, as the epoch length increased, values for the intensity of running actions decreased (e.g., For the backs using the ROLL method, distance covered decreased from 177.4 ± 20.6 m·min-1 in the 60 s epoch to 107.5 ± 13.3 m·min-1 for the 300 s epoch). For the team as a whole, and irrespective of position, estimates of fixed effects indicated significant between-method differences across all time-points for both relative distance covered and HSR. Movement demands were underestimated consistently by FIXED versus ROLL with differences being most pronounced using 60 s epochs (95% CI HSR: -6.05 to -4.70 m·min-1, 95% CI distance: -18.45 to -16.43 m·min-1). For all HSR time epochs except one, all backs groups increased more (p < 0.01) from FIXED to ROLL than the forward groups. Linear mixed modelling of ROLL data highlighted that for HSR (except 60 s epoch), SR was the only group not significantly different to FR. For relative distance covered all other position groups were greater than the FR (p < 0.05). The FIXED method underestimated both relative distance (~11%) and HSR values (up to ~20%) compared to the ROLL method. These differences were exaggerated for the HSR variable in the backs position who covered the greatest HSR distance; highlighting important consideration for those implementing the FIXED method of analysis. The data provides coaches with a worst-case scenario reference on the running demands required for periods of 60–300 s in length. This information offers novel insight into game demands and can be used to inform the design of training games to increase specificity of preparation for the most demanding phases of matches.

In the eastern and central Pacific Ocean the most profound change in Neogene calcium carbonate deposition occurred at the late/middle Miocene boundary (about 10 Ma), when carbonate mass accumulation rates (MARs) abruptly dropped. East of the East Pacific Rise (EPR), carbonate deposition essentially ceased. The carbonate compensation depth (CCD) in the Guatemala Basin, for example, rose by 800 m in less than 0.5 Ma. Even the rise crests suffered carbonate losses-Site 846, at the time less than 300 meters deeper than the EPR axis, experienced intervals between 10 and 9 Ma where no carbonate at all was buried. By about 8 Ma carbonate deposition resumed and was concentrated along an equatorial band, suggestive of high surface water carbonate production. East of the EPR, however, CCDs remained shallow since 10 Ma. This event which we have termed the late Miocene carbonate crash marks a fundamental paleoceanographic change that occurred in the eastern Pacific Ocean. Here, we document the changing pattern of carbonate deposition from 13 Ma to 5 Ma by using maps of carbonate MAR reconstructed from ODP Leg 138 and DSDP data. Comparisons to modern Oceanographic conditions demonstrate that the late Miocene carbonate crash could not have been caused by an abrupt increase in productivity at 10 Ma or by loss of C org from continental shelves. Instead it was probably caused by a relatively small reduction in deep-water exchange between the Atlantic and Pacific Oceans through the Panama Gateway prior to the emergence of the isthmus. A small restriction of deep-water exchange through this gateway is sufficient to radically change carbonate MARs in the eastern Pacific.

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