Description: Throughout the summer seasons 2017 to 2019 snow profiles were taken repeatedly. The sample positions are aligned along a 300 m wind-parallel transect at the EastGRIP ice core deep drilling site. The snow was collected at 6 positions with a 20 – 50 m spacing. Snow was sampled using carbon fiber tubes of 1-m length that were pushed gently into the snow. A maximum compaction of 1 cm was observed during extraction. The snow cores were carefully removed from the carbon fiber tubes on the cutting table. The core was then cut into slices of 1 cm thickness for the upper 10 cm and 2 cm thickness for the lower 90 cm. The samples were placed into Whirl-Pak® bags and closed airtight. The samples were shipped frozen to the Alfred-Wegener-Institut and stored at -25 °C. Prior to measurements, the samples were melted in the sample bags at room temperature. For the measurement of the isotopic composition, the instrument Picarro L2130-i were used. The measurement set-up followed the Van-Geldern protocol (Van Geldern and Barth, 2012). Each sample was injected 4 times unless otherwise noted in the comment column. As a measure of accuracy, we calculated the combined standard uncertainty (Magnusson, et al., 2017) including the long-term reproducibility and bias of our laboratory by measuring a quality check standard in each measurement run and including the uncertainty of the certified standards. The combined uncertainty for δ18O is 0.11 ‰ and for δ2H is 0.8 ‰. Deuterium excess is calculated as both 1) d = dD - 8*d18O; (Merlivat and Jouzel, 1979) and 2) dln = ln(dD + 1) - 8.47(ln(d18O+1)) - 28.5(ln(d18O+1))2; (Uemura et al., 2012).

Description: The last two abrupt warmings at the onset of our present warm interglacial period, interrupted by the Younger Dryas cooling event, were investigated at high temporal resolution from the North Greenland Ice Core Project ice core. The deuterium excess, a proxy of Greenland precipitation moisture source, switched mode within 1 to 3 years over these transitions and initiated a more gradual change (over 50 years) of the Greenland air temperature, as recorded by stable water isotopes. The onsets of both abrupt Greenland warmings were slightly preceded by decreasing Greenland dust deposition, reflecting the wetting of Asian deserts. A northern shift of the Intertropical Convergence Zone could be the trigger of these abrupt shifts of Northern Hemisphere atmospheric circulation, resulting in changes of 2 to 4 kelvin in Greenland moisture source temperature from one year to the next.

Description: Stable water vapor isotopologues (d18O and dD) and mixing ratio (ppmv) observations from 2.5 m and 50 m levels above sea level surface. The data was collected between 2013-06-20 and 2013-12-30 at the Tudor Hill Marine Atmospheric Observatory (THMAO) tower of Bermuda Institute of Ocean Sciences (32.2647° N 64.8788° W). Water vapor observations were collected to study isotopic fractionation processes during ocean evaporation. The instrument used was a Picarro cavity ring-down spectroscopy analyzer (model L-2120i). The data was corrected for the humidity-isotope response of the instrument and calibrated on the VSMOW-SLAP scale. Observations at the two inlets are synchronised and resampled every 30 minutes using a common UTC timestamp (Zannoni et al., 2022). The estimated precision is 0.14 ‰ for d18O and 1.1‰ for dD following Steen-Larsen et al. (2014).

Description: We present here a high resolution water isotope (18O/16O, 2H/1H) record from the NEEM ice core covering the period 8 - 129 ky b2k. The depth resolution of the record is 0.05 m. The analysis has been performed using Cavity Ring Down Spectroscopy with an average precision for the whole record equal to 0.05 and 0.3 ‰ for δ18O and δD respectively. Measurements are calibrated and reported on the SMOW/SLAP scale using a 2-fixed-point calibration. Results are also reported on the GICC05 and AICC2012 timescale.

Description: Mantle volatiles are transported to Earth’s crust and surface by basaltic volcanism. During subaerial eruptions, vast amounts of carbon, sulfur and halogens can be released to the atmosphere during a short time-interval, with impacts ranging in scale from the local environment to the global climate. By contrast, passive volatile release at the surface originating from magmatic intrusions is characterized by much lower flux, yet may outsize eruptive volatile quantities over long timescales. Volcanic hydrothermal systems (VHSs) act as conduits for such volatile release from degassing intrusions and can be used to gauge the contribution of intrusive magmatism to global volatile cycles. Here, we present new compositional and isotopic (δD and δ18O-H2O, 3He/4He, δ13C-CO2, Δ33S- δ34S-H2S and SO4) data for thermal waters and fumarole gases from the Askja and Kverkfj¨oll volcanoes in central Iceland. We use the data together with magma degassing modelling and mass balance calculations to constrain the sources of volatiles in VHSs and to assess the role of intrusive magmatism to the volcanic volatile emission budgets in Iceland. The CO2/ΣS (10􀀀 30), 3He/4He (8.3–10.5 RA; 3He/4He relative to air), δ13C-CO2 (􀀀 4.1 to 􀀀 0.2 ‰) and Δ33S- δ34S-H2S (􀀀 0.031 to 0.003 ‰ and 􀀀 1.5 to +3.6‰) values in high-gas flux fumaroles (CO2 〉 10 mmol/mol) are consistent with an intrusive magmatic origin for CO2 and S at Askja and Kverkfj¨oll. We demonstrate that deep (0.5–5 kbar, equivalent to ~2–18 km crustal depth) decompression degassing of basaltic intrusions in Iceland results in CO2 and S fluxes of 330–5060 and 6–210 kt/yr, respectively, which is sufficient to account for the estimated CO2 flux of Icelandic VHSs (3365–6730 kt/yr), but not the VHS S flux (220–440 kt/yr). Secondary, crystallization-driven degassing from maturing intrusions and leaching of crustal rocks are suggested as additional sources of S. Only a minor proportion of the mantle flux of Cl is channeled via VHSs whereas the H2O flux remains poorly constrained, because magmatic signals in Icelandic VHSs are masked by a dominant shallow groundwater component of meteoric water origin. These results suggest that the bulk of the mantle CO2 and S flux to the atmosphere in Iceland is supplied by intrusive, not eruptive magmatism, and is largely vented via hydrothermal fields.

Description: Published

Description: 107776

Description: OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametrici

Description: JCR Journal