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With the onset of anthropogenic climate change, it is vital that we understand climate sensitivity and rates of change during periods of warming in the Earth's past to properly inform climate forecasts. To best inform modeling of ongoing and future changes, environmental conditions during past periods of extreme warmth are ideally developed from multiproxy approaches, including the development of novel proxies where traditional approaches fail. This study builds on a proposed sea surface temperature (SST) proxy for the high-latitude Southern Ocean, based on the morphometrics of the ubiquitous Antarctic diatom Fragilariopsis kerguelensis. This species has been shown to display two distinct morphotypes; a low-rectangularity morphotype is interpreted to be more common in warmer waters while a high-rectangularity morphotype is more common in cooler waters. The proportion of the low-rectangularity morphotype (pLR) has been correlated to SST and summer SST (SSST). Here, we examine this proxy by reconstructing SST using sediment samples from the modern seafloor surface in the Amundsen Sea and the Sabrina Coast to test how well two published calibrations of this relationship (Kloster et al., 2018; Glemser et al., 2019) reconstruct SST and SSST in the modern ocean. In the Amundsen Sea surface sediments, we calculate derived SST −1.6 to −1.2 °C and derived SSST 0.6 to 0.7 °C. In the Sabrina Coast surface sediments, we calculate derived SST −0.3 to 0.5 °C and derived SSST 1.4 to 2.5 °C. We discuss the differing population dynamics of F. kerguelensis in our surface samples between the Amundsen Sea and Sabrina Coast because the Amundsen Sea specimens display a lower pLR than Sabrina Coast specimens, although they exist in warmer waters and should display a higher pLR. We also use the two published calibrations to preliminarily reconstruct SST and SSST in the Amundsen Sea over the last interglacial, Marine Isotope Stage 5 (MIS-5). We calculate SSTs that are slightly cooler or within the range of the modern Amundsen Sea for the duration of the last interglacial; we calculate summer SSTs ∼ 1 °C warmer than the modern Amundsen Sea. This suggests MIS-5 SSTs were at most marginally warmer than the modern Amundsen Sea.

Iceberg influence on diatom productivity has been observed for the present and suggested for the past, but direct seeding of the Southern Ocean during times of ice sheet collapse has never been directly demonstrated. Here we demonstrate enhanced diatom production and accumulation in the Amundsen Sea during a Mid-Pliocene interglacial that precisely coincides with pulses of ice-rafted debris (IRD) accumulation, and we infer a causal relation. International Ocean Discovery Program (IODP) Expedition 379 obtained continuous sediment records from the Amundsen Sea continental rise to document West Antarctic Ice Sheet (WAIS) history in an area currently experiencing the largest ice loss in Antarctica. Scanning electron microscopy (SEM) imagery of Mid-Pliocene interglacial sediments of Marine Isotope Stage (MIS) (GI-17, ∼ 3.9 Ma) documents distinct intervals of IRD-rich diatomite, whereas the overall diatom abundance and concentration of bloom species is relatively low in the absence of visible IRD. Sand- and granule-sized IRD grains are documented fully encased within diatomite laminae, with some displaying soft-sediment micro-deformation formed by grains falling into soft diatom ooze. IRD-rich diatomite layers are often characterized by nearly monospecific assemblages of the pelagic diatom Thalassiothrix antarctica, indicating very high primary productivity as IRD grains fell. Diatom-filled fecal pellets with clusters of barite grains are also documented within some of these laminae, further indicating direct mass sinking of diatom mats. Melting icebergs release soluble nutrients along with IRD; thus the coincidence of IRD and bloom species in Amundsen Sea sediments provides compelling evidence that iceberg discharge and melting directly initiates enhanced diatom productivity in the Southern Ocean. These results may contribute to interpreting past WAIS history by providing another proxy for potential collapse events. Furthermore, we suggest that ice sheet collapse may more broadly enhance Southern Ocean diatom production, which in itself can contribute to increased carbon export, potentially attenuating or countering the warming that may have triggered the collapse.

Abstract While basaltic volcanism is dominant during rifting and continental breakup, felsic magmatism may be a significant component of some rift margins. During International Ocean Discovery Program (IODP) Expedition 396 on the continental margin of Norway, a graphite‐garnet‐cordierite bearing dacitic unit (the Mimir dacite) was recovered in two holes within early Eocene sediments on Mimir High (Site U1570), a marginal high on the Vøring Transform Margin. Here, we present a comprehensive textural, petrological, and geochemical study of the Mimir dacite in order to assess its origin and discuss the geodynamic implications. The major mineral phases (garnet, cordierite, quartz, plagioclase, alkali feldspar) are hosted in a fresh rhyolitic, vesicular, glassy matrix that is locally mingled with sediments. The major element chemistry of garnet and cordierite, the presence of zircon inclusions with inherited cores, and thermobarometric calculations all support an upper crustal metapelitic origin. While most magma‐rich margin models favor crustal anatexis in the lower crust, thermobarometric calculations performed here show that the Mimir dacite was produced at upper‐crustal depths (

Knowledge of past ice sheet configurations is useful for informing projections of future ice sheet dynamics and for calibrating ice sheet models. The topology of grounding line retreat in the Ross Sea sector of Antarctica has been much debated, but it has generally been assumed that the modern ice sheet is as small as it has been for more than 100 000 years (Conway et al., 1999; Lee et al., 2017; Lowry et al., 2019; McKay et al., 2016; Scherer et al., 1998). Recent findings suggest that the West Antarctic Ice Sheet (WAIS) grounding line retreated beyond its current location earlier in the Holocene and subsequently readvanced to reach its modern position (Bradley et al., 2015; Kingslake et al., 2018). Here, we further constrain the post-LGM (Last Glacial Maximum) grounding line retreat and readvance in the Ross Sea sector using a two-phase model of radiocarbon input and decay in subglacial sediments from six sub-ice sampling locations. In addition, we reinterpret high basal temperature gradients, measured previously at three sites in this region (Engelhardt, 2004), which we explain as resulting from recent ice shelf re-grounding accompanying grounding line readvance. At one location – Whillans Subglacial Lake (SLW) – for which a sediment porewater chemistry profile is known, we estimate the grounding line readvance by simulating ionic diffusion. Collectively, our analyses indicate that the grounding line retreated over SLW 4300-2500+1500 years ago, and over sites on Whillans Ice Stream (WIS), Kamb Ice Stream (KIS), and Bindschadler Ice Stream (BIS) 4700-2300+1500, 1800-700+2700, and 1700-600+2800 years ago, respectively. The grounding line only recently readvanced back over those sites 1100-100+200, 1500-200+500, 1000-300+200, and 800±100 years ago for SLW, WIS, KIS, and BIS, respectively. The timing of grounding line retreat coincided with a warm period in the mid-Holocene to late Holocene. Conversely, grounding line readvance is coincident with cooling climate in the last 1000–2000 years. Our estimates for the timing of grounding line retreat and readvance are also consistent with relatively low carbon-to-nitrogen ratios measured in our subglacial sediment samples (suggesting a marine source of organic matter) and with the lack of grounding zone wedges in front of modern grounding lines. Based on these results, we propose that the Siple Coast grounding line motions in the mid-Holocene to late Holocene were primarily driven by relatively modest changes in regional climate, rather than by ice sheet dynamics and glacioisostatic rebound, as hypothesized previously (Kingslake et al., 2018).

High-resolution, well-dated climate archives provide an opportunity to investigate the dynamic interactions of climate patterns relevant for future projections. Here, we present data from a new, annually dated ice core record from the eastern Ross Sea, named the Roosevelt Island Climate Evolution (RICE) ice core. Comparison of this record with climate reanalysis data for the 1979–2012 interval shows that RICE reliably captures temperature and snow precipitation variability in the region. Trends over the past 2700 years in RICE are shown to be distinct from those in West Antarctica and the western Ross Sea captured by other ice cores. For most of this interval, the eastern Ross Sea was warming (or showing isotopic enrichment for other reasons), with increased snow accumulation and perhaps decreased sea ice concentration. However, West Antarctica cooled and the western Ross Sea showed no significant isotope temperature trend. This pattern here is referred to as the Ross Sea Dipole. Notably, during the Little Ice Age, West Antarctica and the western Ross Sea experienced colder than average temperatures, while the eastern Ross Sea underwent a period of warming or increased isotopic enrichment. From the 17th century onwards, this dipole relationship changed. All three regions show current warming, with snow accumulation declining in West Antarctica and the eastern Ross Sea but increasing in the western Ross Sea. We interpret this pattern as reflecting an increase in sea ice in the eastern Ross Sea with perhaps the establishment of a modern Roosevelt Island polynya as a local moisture source for RICE.

This study has evaluated the performance of a newly developed vehicle for administration of a drug in a soft gelatin capsule. The absorption of vitamin K2 in dogs after oral administration of the vitamin in a soft gelatin capsule containing the newly developed vehicle was compared with absorption after administration of a control formulation prepared by encapsulating the contents of a commercially available vitamin K2 capsule (Glakay capsules 15 mg) in the same type of soft gelatin. Under non-fasted conditions the profile of the plasma concentration of vitamin K2 against time for the test formulation was comparable with that for the control formulation in non-fasted dogs. Under fasted conditions, however, both the maximum concentration (Cmax) and the area under the plot of concentration against time (AUC) were significantly smaller for the test formulation than for the control formulation. The Cmax and AUC for the test formulation were about 10 times larger for non-fasted dogs than for fasted dogs whereas values for the control formulation were about twice as large. These results suggest that both formulations might require the presence of food or digestive fluid components, or both, for better absorption of vitamin K2. It seems that although the performances of the test and control formulations were comparable in the presence of these components, the control formulation works better in their absence. It should be also noted that, in contrast with the results from the absorption tests, the dispersibility of the test vehicle in water was much better than that of the control vehicle. This suggests that dispersibility does not significantly affect vitamin K2 absorption. In conclusion, although the new vehicle did not perform better than the control vehicle in terms of vitamin K2 absorption, the performance of the control formulation was comparable for non-fasted dogs. Because the new vehicle contains considerably less surfactant than the vehicles currently used in soft gelatin capsules, it could be a safer alternative for use under non-fasted conditions.

Some glacial sediment samples recovered from beneath the West Antarctic ice sheet at ice stream B contain Quaternary diatoms and up to 10(8) atoms of beryllium-10 per gram. Other samples contain no Quaternary diatoms and only background levels of beryllium-10 (less than 10(6) atoms per gram). The occurrence of young diatoms and high concentrations of beryllium-10 beneath grounded ice indicates that the Ross Embayment was an open marine environment after a late Pleistocene collapse of the marine ice sheet.

Screening of surfactants was carried out to develop an oil in water (o/w) emulsion type new vehicle for a soft gelatin capsule (SGC), using polyethyleneglycol 400 (PEG 400) as hydrophilic phase and medium chain triglyceride (Miglyol 810), propyleneglycol dicaprylate (Sefsol 228) or soybean oil as hydrophobic phase (PEG 400: hydrophobic phase: surfactant = 87:10:3) and by means of simple homogenization. Polyoxyethylene (20) cetylether (BC-20TX), which can form homogeneous and viscous white gels using the above hydrophilic and hydrophobic phase combination, was selected as a model surfactant for developing the new vehicle. Using Miglyol 810 as hydrophobic phase, a model new vehicle formulation (PEG 400:water:Miglyol 810: BC-20TX = 77:10:10:3) was prepared, and its physicochemical properties were evaluated. The particle size distribution of the new vehicle, after diluting about 3000 times with water, ranged from about 0.5 to 50 microns. Furthermore, the new vehicle had thixotropic property at room temperature (about 25 degrees C) and temperature-dependent gel-sol transforming property with the transformation temperature of about 37 degrees C. These properties meet the requirement for encapsulation of the new vehicle in SGC and suggest that it can be expected to form the o/w emulsion state in the aqueous environment in the stomach. The rheological properties would also make it advantageous for use in other dosage forms such as suppository, cataplasm or liniment.

A rapid and simple high-performance liquid chromatographic (HPLC) method for the analysis of docusate sodium in soft gelatin capsules was developed with progesterone as the internal standard. The method requires a reversed-phase column and a paired-ion technique to separate docusate sodium from other components. A C22 column was used with a mobile phase of acetonitrile:water (70:30) containing 0.005 M tetrabutylammonium phosphate. The flow rate was 1.8 mL/min, and the effluent was monitored at 214 nm. Docusate sodium and progesterone had retention times of 4.5 and 6.8 min, respectively. The proposed HPLC method is linear, accurate, and precise. A mean assay value of 99.6% was obtained by the proposed method when five samples, each containing a composite of 10 capsules, were analyzed. The results obtained by the proposed HPLC, tetra-n-butylammonium iodide titration, and USP XXII HPLC methods are compared.