Description: Sea-level rise due to ice loss in the Northern Hemisphere in response to insolation and greenhouse gas forcing is thought to have caused grounding-line retreat of marine-based sectors of the Antarctic Ice Sheet (AIS). Such interhemispheric sea-level forcing may explain the synchronous evolution of global ice sheets over ice-age cycles. Recent studies that indicate that the AIS experienced substantial millennial-scale variability during and after the last deglaciation (roughly 20,000 to 9,000 years ago) provide further evidence of this sea-level forcing. However, global sea-level change as a result of mass loss from ice sheets is strongly nonuniform, owing to gravitational, deformational and Earth rotational effects, suggesting that the response of AIS grounding lines to Northern Hemisphere sea-level forcing is more complicated than previously modelled. Here, using an ice-sheet model coupled to a global sea-level model, we show that AIS dynamics are amplified by Northern Hemisphere sea-level forcing. As a result of this interhemispheric interaction, a large or rapid Northern Hemisphere sea-level forcing enhances grounding-line advance and associated mass gain of the AIS during glaciation, and grounding-line retreat and mass loss during deglaciation. Relative to models without these interactions, the inclusion of Northern Hemisphere sea-level forcing in our model increases the volume of the AIS during the Last Glacial Maximum (about 26,000 to 20,000 years ago), triggers an earlier retreat of the grounding line and leads to millennial-scale variability throughout the last deglaciation. These findings are consistent with geologic reconstructions of the extent of the AIS during the Last Glacial Maximum and subsequent ice-sheet retreat, and with relative sea-level change in Antarctica.

Description: Here we present zircon petrochronological data, tephra whole-rock/glass compositions, and amphibole thermobarometry comprising the last four explosive eruptions of Ilopango Caldera in El Salvador (Tierra Blanca eruptive suite, TB). Our datasets include 238U-230Th disequilibrium geochronology, trace-elements, and oxygen isotope compositions from polished and unpolished zircon crystals analyzed using a CAMECA IMS 1280-HR secondary ion mass spectrometer (SIMS) at Heidelberg University, Germany. Additionally, pumice clasts whole-rock chemical analyses from the TB suite were performed at the German Research Centre for Geosciences (GFZ) using a PANalytical AXIOS Advanced wavelength-dispersive spectrometer, whereas major and trace-elements, glass shard, and mineral compositions were collected using an electron microprobe analysis (EMPA) at GEOMAR - Helmholtz-Centre for Ocean Research Kiel and by Laser Ablation Inductively Coupled Plasma - Mass Spectrometry (LA-ICP-MS) at Institute of Earth Sciences, Academia Sinica in Taipei. Whole-rock Sr-Nd isotope determinations were carried out at Departamento de Geología, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE; Mexico) with a Nu-Instruments thermal ionization mass spectrometer (Nu-TIMS), whereas whole-rock U-series were determined using a ThermoFisher Neptune inductively-coupled mass-spectrometer multi-collector (ICP-MS-MC) at the University of Wyoming (UWYO, USA).

Description: Aquatic eddy covariance oxygen flux was determined over two seagrass (Posidonia oceanica) meadows at Elba, Italy. The first meadow (open-water) was located 300 m from the southwest corner of the island, and was studied over two continuous days from 15 to 18 May 2016. The second meadow (nearshore) was located 60 m from the north shore of the island, and was studied over two discontinuous days on 13 and 25 May 2017. Both meadows were located at 13 m depth. Eddy covaraince instruments were mounted to a lightweight frame and positioned over seagrass meadows such that the measurement volume was approximately 0.3 m above the top of the canopy. Eddy covariance velocity data were collected at 16 Hz with an acoustic Doppler velocimeter (Vector, Nortek-AS, Norway). Measurements of turbulent fluctuations in oxygen concentration were made 2 cm outside the measuring volume of the Vector using an optode minisensor (O2 Minisensor, Pyroscience GmbH, Germany). The 90% response time of the minisensor was less than 0.3 s. Stable oxygen measurements above and within the canopy were determined with galvanic oxygen sensors (OxyGuard, RBR Ltd., Canada). Eddy covariance fluxes were calculated from the product of turbulent fluctuations in vertical water velocity and oxygen concentration according to standard techniques (see Berg et al., 2003 for details on the aquatic eddy covariance technique, doi:10.3354/meps261075). Further details on calculations of flux, and their correction for the nighttime depletion of oxygen within the seagrass canopy, are presented in the linked manuscript (Koopmans et al., 2020, doi:10.3389/fmars.2020.00118).

Description: This dataset includes results from oxygen isotope compositions from zircon crystal interiors (polished sections) of the Tierra Blanca Joven (TBJ) eruption from Ilopango caldera in El Salvador. Zircon crystals were analyzed employing Secondary Ion Mass Spectrometry at Heidelberg University.

Description: This dataset includes results from U-Pb dating from zircon crystal interiors (polished sections) of the Tierra Blanca Joven eruption (TBJ) from Ilopango caldera in El Salvador. Zircon crystals were analyzed employing Secondary Ion Mass Spectrometry at Heidelberg University.

Description: This dataset includes results from U-Th disequilibria dating from zircon rims (outermost crystal face) and crystal interiors (polished crystals) of the last four explosive silicic eruptions from Ilopango caldera in El Salvador (TBJ, TB2, TB3, and TB4). Zircon crystals were analyzed employing Secondary Ion Mass Spectrometry at Heidelberg University.

Description: This dataset includes results from trace element concentrations from zircon rims (outermost crystal face) and crystal interiors (polished sections) of the last four explosive silicic eruptions from Ilopango caldera (TBJ, TB2, TB3, and TB4) in El Salvador. Zircon crystals were analyzed employing Secondary Ion Mass Spectrometry at Heidelberg University.

Description: This dataset includes results from U-series and Sr-Nd whole-rock isotope compositions of the last four explosive silicic eruptions from Ilopango caldera in El Salvador (TBJ, TB2, TB3, and TB4). Sr and Nd isotope ratios were measured with a Nu Instruments thermal ionization mass spectrometer (Nu-TIMS) at Departamento de Geología, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE) in the state of Baja California (Mexico), whereas U and Th concentrations and isotopes were measured at University of Wyoming (UWYO) were measured by isotope dilution using a ThermoFisher Neptune ICP-MS multicollector.

Description: This dataset includes results from amphibole geothermobarometry of explosive silicic eruptions from Ilopango caldera in El Salvador (TBJ, TB2, TB3, and TB4). Amphibole compositions were analyzed employing a JEOL JXA 8200 wavelength dispersive microprobe at the GEOMAR - Helmholtz-Centre for Ocean Research Kiel.