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Between 1992 and 2018, the breeding population of Adélie penguins around Anvers Island, Antarctica declined by 98%. In this region, natural climate variability drives five‐year cycling in marine phytoplankton productivity, leading to phase‐offset five‐year cycling in the size of the krill population. We demonstrate that the rate of change of the Adélie breeding population also shows five‐year cycling. We link this population response to cyclical krill scarcity, a phenomenon which appears to have arisen from the interaction between climate variability and climate change trends. Modeling suggests that, since at least 1980, natural climate variability has driven cycling in this marine system. However, anthropogenic climate change has shifted conditions so that fewer years in each cycle now prompt strong krill recruitment, triggering intervals of krill scarcity that result in drastic declines in Adélie penguins. Our results imply that climate change can amplify the impacts of natural climate oscillations across trophic levels, driving cycling across species and disrupting food webs. The findings indicate that climate variability plays an integral role in driving ecosystem dynamics under climate change.

Textural and compositional attributes of dolomite and calcite within Lower Cretaceous Peterson Limestone micrite indicate that these phases coprecipitated during stabilization of precursor magnesian calcite in a largely closed diagenetic system. Uniform difference in the isotopic compositions of contained carbonate phases over a range of whole rock compositions reflect equilibrium partitioning of18O and13C between dolomite and calcite. Diagenetic dolomite is enriched in18O by 4.4 o/oo and in13C by 1.8 o/oo relative to co-existing calcite, values which are discemibly different from expected open system mixing trends, and which are in general agreement with high temperature fractionation data extrapolated to sedimentary temperatures as well as with calculated δ18O dolomite-calcite from Holocene dolomites.

δ 18O measurements of benthic ostracodes are used to reconstruct the δ 18O history of Lake Huron and Georgian Bay water between 10,600 and 7600 14C yr B.P. This δ 18O record was calibrated using a comparison of the δ 18O values of modern ostracodes and Lake Huron water, where a fractionation of 1.0358 was measured between the oxygen isotope ratios of the most isotopically positive ostracode Candona subtriangulataand lake water. The most positive shell δ 18O value was used because it is precipitated in the cold (0° to 2°C) water common to both deep and shallow environments. The δ 18O of Lake Huron water reflects a large glacial meltwater component for much of its history before 7600 14C yr B.P. Times of low lake level correlate with the highest ratio of glacial meltwater to local precipitation in the basin (most negative δ 18O values). Georgian Bay water was more negative in δ 18O than Lake Huron water of the same age; this reflects a higher proportion of glacial meltwater in Georgian Bay and its separation from Lake Huron during times of low lake level.

Detailed investigations of high latitude sequences recently collected by the Ocean Drilling Program (ODP) indicate that periods of rapid climate change often culminated in brief transient climates, with more extreme conditions than subsequent long term climates. Two examples of such events have been identified in the Paleogene; the first in latest Paleocene time in the middle of a warming trend that began several million years earlier: the second in earliest Oligocene time near the end of a Middle Eocene to Late Oligocene global cooling trend. Superimposed on the earlier event was a sudden and extreme warming of both high latitude sea surface and deep ocean waters. Imbedded in the latter transition was an abrupt decline in high latitude temperatures and the brief appearance of a full size continental ice-sheet on Antarctica. In both cases the climate extremes were not stable, lasting for less than a few hundred thousand years, indicating a temporary or transient climate state. Geochemical and sedimentological evidence suggest that both Paleogene climate events were accompanied by reorganizations in ocean circulation, and major perturbations in marine productivity and the global carbon cycle. The Paleocene-Eocene thermal maximum was marked by reduced oceanic turnover and decreases in global $$\delta^{13}C $$and in marine productivity, while the Early Oligocene glacial maximum was accompanied by intensification of deep ocean circulation and elevated $$\delta^{13}C $$and productivity. It has been suggested that sudden changes in climate and/or ocean circulation might occur as a result of gradual forcing as certain physical thresholds are exceeded. We investigate the possibility that sudden reorganizations in ocean and/or atmosphere circulation during these abrupt transitions generated short-term positive feedbacks that briefly sustained these transient climatic states.

Paleomagnetic study of subsurface samples of the Upper Ordovician Trenton and Black River Limestones collected from six industrial wells in the southern part of the Michigan Basin yields a well-clustered characteristic direction (mean Dec/Inc of 170.6°/ - 10.9°, $$\alpha_{95} = 7.6^\circ$$) after rotation of random declinations by aligning a present day field overprint with geographic north. The corresponding paleomagnetic pole at 52.4°N 111.0°E is similar to those of the remagnetized carbonates in Ontario and New York State, suggesting that the Michigan formations were also remagnetized in the late Paleozoic. Rock magnetic characterizations suggest that the characteristic magnetization is carried by single and pseudosingle domain magnetite grains. Very fine rounded single crystal magnetite grains, believed to be products of chemical precipitation, observed by scanning and scanning transmission electron microscope (SEM/STEM) are inferred to be the carrier of the remagnetization. Paired carbon isotope analyses of bulk carbonate and anhysteretic susceptibility ($$X_{arm}$$) of cuttings from two wells were examined to test the hypothesis that oxidation of hydrocarbons may lead to formation of authigenic magnetite. Oil saturated horizons and overlying strata in a producing well exhibit lower $$X_{arm}$$intensities than the equivalent horizons in an adjacent non-producing well. Little correlation between $$X_{arm}$$and $$\delta^{13}C$$is observed in carbonate-rich lithologies due to the masking of the hydrocarbon related cement compositions by the host carbonate. In contrast, carbonate-poor shale horizons overlying hydrocarbon-rich strata in the producing well exhibit strong correlative peaks in $$X_{arm}$$and $$\delta^{13}C$$. The overall lower $$X_{arm}$$intensities in the hydrocarbon-producing well suggest that it is not merely the presence of hydrocarbons which promotes authigenic magnetite formation. Rather, the magnetite/hydrocarbon relationship more likely records processes associated with hydrocarbon migration and interaction with oxidizing subsurface fluids in areas peripheral to sites of accumulation.

Minor element and isotopic compositions of marine bivalve calcite are frequently used as proxy records of seawater temperature and salinity. Although molluscan calcite is secreted at or near oxygen isotope equilibrium, the influence of metabolic activity (i.e., vital effects) on skeletal SrCaratios and δ 13C values is not well known. We present measurements of skeletal chemistry from (a) consecutive samples milled in chronological order from the organism's final year of growth and (b) adjacent samples within three separate growth bands of the marine mussel Mytilus trossulusto investigate chemical disequilibrium effects among different parts of the shell.

Coagulation tests were performed before and after institution of conventional therapy, and after clinical remissions, in 35 nonazotemic patients with nephrotic syndrome. Pretreatment studies revealed elevated levels of plasma fibrinogen, factors V, combined VII and X, and VIII, mild thrombocytosis, and accelerated thromboplastin generation. Several thromboembolic complications occurred in these patients and anticoagulant therapy was given to two of them. The abnormal results of tests tended to normalize with clinical remission. It is concluded that the nephrotic syndrome is often associated with blood hypercoagulability and a risk of thromboembolism, and that this may be enhanced by corticosteroid therapy. When renal vein thrombosis occurs it is probably another manifestation of the hypercoagulable state more often than a de novo cause of nephrotic syndrome. Long-term anticoagulant therapy may have a place in the management of nephrotic patients.

Faunal analog reconstructions suggest that Last Interglacial (MIS 5e) sea surface temperatures were cooler around Bermuda and in the Caribbean than modern climate. Here we describe new and revised clumped isotope measurements of Cittarium picafossil shells supporting previous findings of cooler than modern temperatures in Bermuda during the Last Interglacial. We resolve temperature and δ18Owdifferences between two closely located and apparently coeval sites described in Winkelstern et al. (2017), https://doi.org/10.1002/2016pa003014through reprocessing raw isotopic data with the updated Brand/IUPAC parameters. New subannual‐resolution clumped isotope data reveal large variations in δ18Owout of phase with seasonal temperature changes (i.e., lower δ18Owvalues in winter). Supported by modern δ18Owmeasurements identifying similar processes occurring today, we suggest past variations in coastal δ18Owwere driven by seasonally variable freshwater discharge from a subterranean aquifer beneath the island. Taken together, our results emphasize the importance of δ18Owin controlling carbonate δ18O, and suggest that typical assumptions of constant δ18Owshould be made cautiously in nearshore settings and can contribute to less accurate reconstructions of paleotemperature. Bermudan climate during the Last Interglacial period (MIS 5e) was colder than todaySubannual clumped isotope analyses capture seasonal‐scale changes in temperature and water compositionVariable discharge from an underground aquifer affects oxygen isotopic composition of coastal water during MIS 5e and today Bermudan climate during the Last Interglacial period (MIS 5e) was colder than today Subannual clumped isotope analyses capture seasonal‐scale changes in temperature and water composition Variable discharge from an underground aquifer affects oxygen isotopic composition of coastal water during MIS 5e and today

The oxygen isotopic compositions of tests of Foraminifera are quantitatively related to global ice volume1,2and local temperature and salinity conditions in which the Foraminifera grew3–8. Thus, a well-preserved sample of deep-sea core contains information about sea-surface temperature (shallow-dwelling planktonic Foraminifera), structure of the thermocline (deeper-dwelling planktonic Foraminifera), and bottom water temperature (benthic Foraminifera), and the global ice volume effect is also superimposed. The progress which has been made in calibration of core–top isotopic data to modern oceanographic data5,7,8, has led us to test state-of-the-art core–top methodology and calibration on a late Miocene time slice (6.0 ± 0.5 Myr BP) of the Atlantic Ocean. Samples studied can be related to either uppermost Zone NN11 or lowermost NN12 of Martini9and uppermost Zone N17 of Blow10.