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The Late Neogene to Quaternary periods include several climate and tectonic events that brought the surface ocean circulation system into its modern configuration. Characterizing how surface conditions, namely temperature and salinity gradients, behaved in response to cooling and warming events has implications for understanding past atmospheric and biotic processes and how the Earth system may respond to increased anthropogenic warming. One region that lacks long-term geochemical records is the Tasman Sea, southwest Pacific Ocean. This region is characterized by a major western boundary current and its extensional flow, which creates large temperature gradients within the basin. Prior geochemical analyses indicate this region warmed and cooled in response to tectonic gateway closures. To build on these geochemical data sets and create a transect across the northern Tasman Sea, we use δ18O and δ13C measurements from the mixed-layer planktic foraminifera species Trilobatus sacculifer to reconstruct surface ocean conditions from the Middle Miocene to early Pleistocene (12–2.3 Ma) at International Ocean Discovery Program Site U1506. We find that surface ocean conditions at the site oscillated through time, with some major stepped changes in the isotopic values through the Miocene. Additional geochemical time series developed in the future from more central and southern Tasman Sea sites will aid in understanding the development and behavior of such frontal boundary systems through the Neogene. 

The high-energy radiative output, from the X-ray to the ultraviolet, of exoplanet host stars drives photochemical reactions and mass loss in the upper regions of planetary atmospheres. In order to place constraints on the atmospheric properties of the three closest terrestrial exoplanets transiting M dwarfs, we observe the high-energy spectra of the host stars LTT 1445A and GJ 486 in the X-ray withXMM-NewtonandChandraand in the ultraviolet with HST/COS and STIS. We combine these observations with estimates of extreme-ultraviolet flux, reconstructions of the Lyαlines, and stellar models at optical and infrared wavelengths to produce panchromatic spectra from 1 Å to 20 µm for each star. While LTT 1445Ab, LTT 1445Ac, and GJ 486b do not possess primordial hydrogen-dominated atmospheres, we calculate that they are able to retain pure CO₂atmospheres if starting with 10, 15, and 50% of Earth’s total CO₂budget, respectively, in the presence of their host stars’ stellar wind. We use age-activity relationships to place lower limits of 2.2 and 6.6 Gyr on the ages of the host stars LTT 1445A and GJ 486. Despite both LTT 1445A and GJ 486 appearing inactive at optical wavelengths, we detect flares at ultraviolet and X-ray wavelengths for both stars. In particular, GJ 486 exhibits two far-ultraviolet flares with absolute energies of 10^29.5and 10^30.1erg (equivalent durations of 4357 ± 96 and 19 724 ± 169 s) occurring 3 h apart. Based on the timing of the observations, we suggest that these high-energy flares are related and indicative of heightened flaring activity that lasts for a period of days, but our interpretations are limited by sparse time-sampling. Consistent high-energy monitoring is needed to determine the duration and extent of high-energy activity on individual M dwarfs and the population as a whole.