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Offshore Antarctic polynyas—large openings in the winter sea ice cover—are thought to be maintained by a rapid ventilation of deep-ocean heat through convective mixing. These rare phenomena may alter abyssal properties and circulation, yet their formation mechanisms are not well understood. Here we demonstrate that concurrent upper-ocean preconditioning and meteorological perturbations are responsible for the appearance of polynyas in the Weddell Sea region of the Southern Ocean. Autonomous profiling float observations—collected in 2016 and 2017 during the largest polynyas to form near the Maud Rise seamount since 1976—reveal that the polynyas were initiated and modulated by the passage of severe storms, and that intense heat loss drove deep overturning within them. Wind-driven upwelling of record strength weakened haline stratification in the upper ocean, thus favouring destabilization in 2016 and 2017. We show that previous Weddell polynyas probably developed under similarly anomalous conditions, which are associated with a mode of Southern Hemisphere climate variability that is predicted to strengthen as a result of anthropogenic climate change. Measurements collected during recent polynya events in the Southern Ocean reveal that these sea ice openings formed as a result of weakened stratification and severe storms and were sustained by deep overturning.

Melt rates of West Antarctic ice shelves in the Amundsen Sea track large decadal variations in the volume of warm water at their outlets. This variability is generally attributed to wind‐driven variations in warm water transport toward ice shelves. Inspired by conceptual representations of the global overturning circulation, we introduce a simple model for the evolution of the thermocline, which caps the warm water layer at the ice‐shelf front. This model demonstrates that interannual variations in coastal polynya buoyancy forcing can generate large decadal‐scale thermocline depth variations, even when the supply of warm water from the shelf‐break is fixed. The modeled variability involves transitions between bistable high and low melt regimes, enabled by feedbacks between basal melt rates and ice front stratification strength. Our simple model captures observed variations in near‐coast thermocline depth and stratification strength, and poses an alternative mechanism for warm water volume changes to wind‐driven theories. Ice loss from the West Antarctic Ice Sheet contributes significantly to current and projected rates of global sea‐level rise. The ice sheet is primarily losing mass via glaciers that flow from the Antarctic continent into the Amundsen Sea, where floating ice shelves are exposed to much warmer ocean waters than elsewhere around Antarctica. In this work we present a simplified mathematical model for the volume of warm water at Amundsen Sea ice shelf fronts that reproduces observed patterns of warm water variability. The modeled variability relies on interactions between ice shelf melt and coastal polynyas, regions where enhanced wintertime sea‐ice production can trigger mixing that diverts heat carried by warm waters away from the ice shelf and into the atmosphere. Higher melt rates inhibit polynya convection, allowing more warm water into the ice shelf cavity and reinforcing a high melt state, whilst lower melt rates facilitate polynya convection, diverting heat away from the ice shelf and reinforcing a low melt state. Interannual variations in polynya sea‐ice production trigger shifts between these reinforcing states. Our results promote the importance of coastal processes in explaining observed variations in Amundsen Sea ice shelf melt, which have previously been attributed to remote wind patterns. Rates of ocean‐driven Amundsen Sea ice shelf melt respond to variations in warm water transport to the coast and modification at the coastA simple Amundsen Sea continental shelf overturning model, based on water mass transformation, reveals bistable high and low melt regimesFeedbacks between glacial melt and polynya convection are central to the bistability and produce variability consistent with observations Rates of ocean‐driven Amundsen Sea ice shelf melt respond to variations in warm water transport to the coast and modification at the coast A simple Amundsen Sea continental shelf overturning model, based on water mass transformation, reveals bistable high and low melt regimes Feedbacks between glacial melt and polynya convection are central to the bistability and produce variability consistent with observations

Southern Ocean sea ice plays a central role in the oceanic meridional overturning circulation, transforming globally prevalent watermasses through surface buoyancy loss and gain. Buoyancy loss due to surface cooling and sea ice growth promotes the formation of bottom water that flows into the Atlantic, Indian, and Pacific basins, while buoyancy gain due to sea ice melt helps transform the returning deep flow into intermediate and mode waters. Because northward expansion of Southern Ocean sea ice during the Last Glacial Maximum (LGM; 19–23 kyr BP) may have enhanced deep ocean stratification and contributed to lower atmospheric CO2levels, reconstructions of sea ice extent are critical to understanding the LGM climate state. Here, we present a new sea ice proxy based on the 18O/16O ratio of foraminifera (δ18Oc). In the seasonal sea ice zone, sea ice formation during austral winter creates a cold surface mixed layer that persists in the sub‐surface during spring and summer. The cold sub‐surface layer, known as winter water, sits above relatively warm deep water, creating an inverted temperature profile. The unique surface‐to‐deep temperature contrast is reflected in estimates of equilibrium δ18Oc, implying that paired analysis of planktonic and benthic foraminifera can be used to infer sea ice extent. To demonstrate the feasibility of the δ18Ocmethod, we present a compilation of N. pachydermaand Cibicidoidesspp. results from the Atlantic sector that yields an estimate of winter sea ice extent consistent with modern observations. Sea ice coverage in the Southern Ocean plays a critical role in Earth’s climate system by influencing ocean‐atmosphere gas exchange and the global ocean circulation. While satellite observations provide detailed information on sea ice cover in the modern era, the satellite record is only a few decades in duration, limiting our long‐term perspective. An improved understanding of sea ice requires reconstructions in the geologic past under climate conditions different than today. Here, we propose a new technique for reconstructing sea ice extent in the Southern Ocean based on the 18O/16O ratio (δ18Oc) of foraminifera. The δ18Ocof foraminifera is sensitive to temperature and it can therefore be used to infer areas of surface cooling where sea ice tends to form and warmer areas where sea ice melts. We present an initial compilation of data showing that the δ18Ocmethod yields an estimate of modern sea ice extent consistent with satellite observations, highlighting the potential of the δ;18Ocmethod for paleoclimate studies. Southern Ocean winter water and sea ice extent can be reconstructed using the oxygen isotopic composition of planktonic and benthic foraminiferaSummertime calcification of the planktonic foraminifer N. pachydermalikely occurs in sub‐surface winter waterPreliminary sea ice reconstruction for the late Holocene is consistent with satellite‐base estimates in the Atlantic sector of the Southern Ocean Southern Ocean winter water and sea ice extent can be reconstructed using the oxygen isotopic composition of planktonic and benthic foraminifera Summertime calcification of the planktonic foraminifer N. pachydermalikely occurs in sub‐surface winter water Preliminary sea ice reconstruction for the late Holocene is consistent with satellite‐base estimates in the Atlantic sector of the Southern Ocean

A study of some biochemical properties of alkaline phosphatase derived from human endometrium has been undertaken. The endometrial enzyme has been shown to be different from alkaline phosphatases obtained from placenta and small intestine. Endometrial alkaline phosphatase is inhibited by sodium deoxycholate but not by l-phenylalanine; it is completely inhibited by 3M urea. Magnesium ions have no significant effect on the endometrial enzyme. No differences in biochemical properties were observed when alkaline phosphatase from follicular phase endometrium was compared with that from luteal phase tissue. Acrylamide gel electrophoresis showed a single, constant band of enzyme at all stages of the cycle. It is concluded that, despite the cyclic appearance of alkaline phosphatase in endometrial glands and the constant presence of the enzyme in blood vessels, there is but one variety of alkaline phosphatase in human endometrium.

When the umbilical cord is clamped immediately after birth, over 100 cc. of blood can usually be obtained from the placental end of the cord.1 This blood normally flows into the infant if clamping is delayed until the placenta begins to descend into the vagina.2 During the neonatal period the infant's total blood volume is about 10 per cent of the body weight,3 and the average weight at birth is about 3.2 Kg.; therefore it is possible that the blood contained in the placenta and its surface vessels is equivalent to a third of the blood volume of the newborn infant. We have shown previously that depriving the infant of the placental blood results in a significant decrease in the erythrocyte count and the hemoglobin content of the blood and an increase in the reticulocytes during the first week of life.2c Further observations have indicated that

In cold polar waters, temperatures sometimes drop below the freezing point, a process referred to as supercooling. However, observational challenges in polar regions limit our understanding of the spatial and temporal extent of this phenomenon. We here provide observational evidence that supercooled waters are much more widespread in the seasonally ice‐covered Southern Ocean than previously reported. In 5.8% of all analyzed hydrographic profiles south of 55°S, we find temperatures below the surface freezing point (“potential” supercooling), and half of these have temperatures below the local freezing point (“in situ” supercooling). Their occurrence doubles when neglecting measurement uncertainties. We attribute deep coastal‐ocean supercooling to melting of Antarctic ice shelves and surface‐induced supercooling in the seasonal sea‐ice region to wintertime sea‐ice formation. The latter supercooling type can extend down to the permanent pycnocline due to convective sinking plumes—an important mechanism for vertical tracer transport and water‐mass structure in the polar ocean. Ocean water, which contains about 34 grams of salt per kilogram of seawater, generally freezes around −1.85°C. However, seawater can be cooled to even lower temperatures without turning into ice. This phenomenon is called supercooling. Supercooled water is found in the polar oceans, typically in regions where the ocean is in contact with ice, as is the case for the enormous seasonal sea‐ice region around Antarctica. But collecting measurements in this region under the thick ice cover during the dark and cold Antarctic winter is challenging. Here, we supplement rather sparse traditional ship‐based observations with data collected by autonomous floats and instrumented marine mammals to detect and analyze where, when, and how supercooled seawater forms in the Southern Ocean. We find widespread supercooling related to melting floating glaciers (ice shelves) along the Antarctic coast and sea‐ice formation. Our analysis enables us to detect sinking supercooled plumes from sea‐ice formation, which may be important for cooling the deep ocean and transporting constituents such as carbon, nutrients, or oxygen from the ocean's surface to deeper layers. Potential and in situ supercooling occurs in large parts of the Southern Ocean seasonal sea‐ice zoneDeep coastal supercooling from below 100 m to the ocean bottom is associated with melting ice shelves and dense shelf water formationShallow supercooling is associated with sea‐ice formation and can penetrate as deep as the permanent pycnocline

HISTOCHEMICAL and biochemical investigations of the human endometrium have revealed variations in the activity of a number of enzymes throughout the normal menstrual cycle1–3. Marked differences in the concentration and localization of enzymes have been found between endometrial gland cells and stromal cells. It is commonly assumed that these variations in enzyme activity are mediated by oestrogens and progesterone. I thought that a more detailed knowledge of hormone action at a cellular level might be obtained by combining organ culture of human endometrium with quantitative histochemical methods. Maurer has, for example, recently demonstrated the value of organ culture techniques for the study of the effects of steroid sex hormones on target tissues in animals4. By the combined techniques I have now detected an increase in malate dehydrogenase activity in the human endometrium stimulated in vitroby oestradiol-17β. The increase in enzyme activity occurs mainly in the cells of the endometrial glands and is suppressed by actinomycin Dand I think that it is due to the formation of new enzyme.

This article presents comments of editors of the May 2004 issue of the periodical "Field & Stream." One of the editors says that in the article "Freedom to Overfish" of the issue, the author asserts that conservation-minded saltwater anglers and groups like the Recreational Fishing Alliance are aiding overfishing and habitat destruction, when nothing could be further from the truth. The Freedom to Fish Act is being promoted to protect recreational fishermen from unwarranted and scientifically unjustified no-take reserves.