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Abstract: Recent studies have correlated dinoflagellate resting cyst morphology to salinity and density variations in the water column, suggesting that morphology can be used for paleoceanographic reconstructions. However, the univariate statistics used by these studies are appropriate only where morphology is related to a single variable. Density is a function of salinity and temperature, so more advanced statistical methods are needed to understand which parameters affect morphology. In this study based on surface (coretop) sediments, a set of environmental variables (sea-surface salinity, temperature, nitrate, and phosphate) was simultaneously correlated to morphological variations seen in resting cysts produced by the dinoflagellate Protoceratium reticulatum (= Operculodinium centrocarpum sensu Wall and Dale). Approximately 3200 measurements were obtained from the North Atlantic Ocean and used to generate a working model based on the Akaike information criterion. Hierarchical partitioning was then applied to establish the independent and joint effects for each predictor variable. Results from these analyses showed that while salinity constitutes the dominant variable affecting process length in the cysts of P. reticulatum in the North Atlantic, it is not the sole explanatory variable and that multicollinearity exists. Temperature and nutrients also showed a significant relationship to the morphology, requiring multiple regression to construct a representative model. The applicability of the North Atlantic working model was finally evaluated by comparing the results to data from the Mediterranean, Marmara, and Black seas, and Baltic–Kattegat–Skagerrak estuarine system. This comparison showed regional differences in morphological–environmental correlation. While salinity constitutes the most important explanatory factor in both the North Atlantic and Baltic–Skagerrak system, this is not so for the Mediterranean–Black Sea region where temperature is the dominant variable. It is concluded that a predictive salinity model based on P. reticulatum cyst morphology has at best a regional application. [Copyright &y& Elsevier]

Abstract: North Atlantic sediment drifts are valuable archives for paleoceanographic reconstructions spanning various timescales. However, the short-term dynamics of such systems are poorly known, and this impinges on our ability to quantitatively reconstruct past change. Here we describe a high-resolution 319-day time-series of hydrodynamics and near-bottom (4m) particulate matter flux variability at a 2600m deep site with an extremely high sediment accumulation rate on the southern Gardar Drift in the North Atlantic. We compare our findings with the actual deposits at the site. The total annual particle flux amounted to ∼360gm−2 yr−1, varied from ∼0.15 to >5.0gm−2 day−1 and displayed strong seasonal compositional changes, with the highest proportion of fresh biogenic matter arriving after the spring bloom in June and July. Flux variability also depended on the changing input of lithogenic matter that had been (re)suspended for a longer time (decades). Active focussing of material from both sources is required to account for the composition and the magnitude of the total flux, which exceed observations elsewhere by an order of magnitude. The enhanced focussing or increased delivery appeared to be positively related to current velocity. The intercepted annual particle flux accounted for only 60% of the sediment accumulation rate of 600±20gm−2 yr−1 (0.20±0.07cmyr−1), indicating higher intra- and inter-annual variability of both the biogenic and lithogenic fluxes and/or advection of additional sediment closer to the seafloor (i.e. <4m). This temporal variability in the composition and amount of material deposited highlights intra-annual changes in the flux of lithogenic material, but also underscores the importance of (reworked) sediment focussing and seasonality of the biogenic flux. All should be taken into account in the interpretation of the paleorecord from such depositional settings. [Copyright &y& Elsevier]

The article discusses the origin of thermostat in the North Atlantic Ocean. The paleoceanographers assumed that thermostat switch which began to melt the world over the last ice age lay somewhere in the North Atlantic Ocean. However, new evidence from the tropical places that it lay in the waters around Antarctica. According to a paleoceanographer Lowell Stott, studying the origin of it comes down to timing, and determining the timing of climate events can be tough as warming in the tropics is recorded in marine sediments, whereas warming in Antarctica is recorded in glacial ice.