ALBERT

Description: Between 1733 and 1895, a total of 35 additional volcanic eruptions were detected in the new high-resolution measurements (D4i dataset: "Greenland ice-core non-sea-salt sulfur concentrations and calculated volcanic sulfate deposition (1733-1900 CE)" (PANGAEA, doi:10.1594/PANGAEA.960977) of the D4 ice core (McConnel et al., 2007). For the same time period only 25 volcanic eruptions had previously been detected using an ice-core array from Greenland (including NEEM-2011-S1 and NGRIP) and Antarctica, making up the eVolv2k database [Toohey and Sigl, 2017]. 21 volcanic events in D4i are found to match events in the eVolv2k database, 8 tropical events and 13 Northern Hemisphere extratropical (NHET) events. Based on linear fits of eVolv2k volcanic stratospheric sulfur injections (VSSI) to the cumulative D4i sulfate deposition rates, we derive scaling factors to convert D4i volcanic sulfate depositions to VSSI. Fits are of high quality with R2 values of 0.91 and 0.99 for tropical and extratropical events, respectively. Of the remaining events identified in D4i but not included in eVolv2k, we find 11 that are tentatively attributable to VEI=4 events listed in the Volcanoes of the World [Global Volcanism Program, 2013] (GVP) database (e.g, Soufriere St. Vincent, and Awu in 1812; Suwanosejima in 1813; Mayon 1814; Raung 1817; Colima 1818). Although attribution is not completely certain, for these events we assume the attribution is correct and use the historically dated eruption date and location from Volcanoes of the World (Global Volcanism Program, 2013). Eruptions found in D4i which do not have a corresponding event in the GVP database could result from a number of scenarios. To avoid a potential bias by attributing these signals to either tropical latitudes (0°) or to NHET latitudes (i.e. 45°N), we represent the forcing by these unidentified events as the probability-weighted superposition of tropical and extratropical eruptions based on the measured sulfate flux. For each event we calculate the VSSI associated with the sulfate deposition assuming on the one hand the event was tropical, and on the other hand assuming it was extratropical. These VSSI values are then multiplied by the probability that the event was either tropical or extratropical, based on the proportion of NHET and tropical events in the Greenland records used in eVolv2k. Each unidentified sulfate deposition is then represented in the VSSI file as two injections, with the same eruption time taken from the ice ice-core dating, and different VSSI amounts for default tropical and extratropical regions. The resulting list of "additional" eruptions not included in eVolv2k is merged with eVolv2k, and the resulting eruption list named eVolv2k plus D4i used as input to the EVA forcing generator [Toohey et al., 2016] to generate time series of stratospheric aerosol optical depth (SAOD).

Description: The West Antarctic Ice Sheet (WAIS) Divide deep ice core WD2014 chronology, consisting of ice age, gas age, delta-age and uncertainties therein. The West Antarctic Ice Sheet Divide (WAIS Divide, WD) ice core is a newly drilled, high-accumulation deep ice core that provides Antarctic climate records of the past ~68 ka at unprecedented temporal resolution. The upper 2850 m (back to 31.2 ka BP; Sigl et al., 2015, Sigl et al., 2016) have been dated using annual-layer counting based on counting of annual layers observed in the chemical, dust and electrical conductivity records. The measurements were interpreted manually and with the aid of two automated methods. We validated the chronology by comparing of the cosmogenic isotope records of 10Be from WAIS Divide and 14C for IntCal13. We demonstrated that over the Holocene WD2014 was consistently accurate to better than 0.5% of the age. The chronology for the deep part of the core (below 2850m; 67.8-31.2 ka BP; Buizert et al., 2015) is based on stratigraphic matching to annual-layer-counted Greenland ice cores using globally well-mixed atmospheric methane. We calculate the WD gas age-ice age difference (Delta age) using a combination of firn densification modeling, ice-flow modeling, and a data set of d15N-N2, a proxy for past firn column thickness. The largest Delta age at WD occurs during the Last Glacial Maximum, and is 525 +/- 120 years. We synchronized the WD chronology to a linearly scaled version of the layer-counted Greenland Ice Core Chronology (GICC05), which brings the age of Dansgaard-Oeschger (DO) events into agreement with the U/Th absolutely dated Hulu Cave speleothem record.

Description: The core depths for GISP2 and the NEEM(2011S1) ice cores for 92 common volcanic deposition events derived from volcanic synchronization of the GISP2 sulphate record against the NEEM(2011-S1) sulphur ice-core record on the NS1-2011 timescale. See Figs. S1-S3, https://doi.org/10.5194/essd-9-809-2017-supplement.

Description: A continuous ice core analytical system was used to analyze the ~410 m NEEM-2011-S1 ice core collected in summer 2011 near the NEEM deep drilling site in NW Greenland. The core was analyzed for a broad range of elements and chemical species using a coupled continuous flow analysis system with two inductively coupled plasma mass spectrometers and single-particle soot photometer. The aerosol records are provided at 2 cm depth resolution to account for signal dispersion in the online analytical system. All records are on the NS1-2011 ice-core chronology: Between 1258 and 1997 CE, this chronology is based on mannual annual-layer counting based on multi-parameter aerosol records constrained by historic volcanic age markers (i.e. Krakatao 1883; Tambora 1815; Laki 1783; Mount Parker 1641; Huaynaputina 1600; Veidivötn 1477; Samalas 1257). Between 86 CE and 1258 CE, this chronology is based on automated annual-layer counting using the StratiCounter program, an automated, objective, annual-layer detection method based on Hidden Markov Model algorithms based on multi-parameter aerosol records and constrained by a solar proton events in 775 and 993 CE, and documentary evidence of volcanic dust veils in 536, 626 and 939 CE.

Description: We present sub-annually resolved concentration records of refractory black carbon (rBC; using soot photometry) as well as distinctive tracers for mineral dust (calcium, sulfate, sodium), biomass burning (ammonium) and industrial pollution (lead, bismuth, ammonium, nitrate) from the Colle Gnifetti (4450 m asl; 45.932°N, 7.876°E) ice core in the Alps from 1741-2015 AD. The data is a composite of two ice cores: CG03B drilled in 2003; CG15 drilled in 2015 at the same site.

Description: Annual-resolved sulfur and non-sea-salt sulfur concentrations and inferred volcanic sulfate depoistion rates from the six ice cores NEEM-2011-S1 (Sigl et al., 2013), NGRIP1 (Plummer et al., 2012), NGRIP2 (McConnell et al., 2018), TUNU2013 (Sigl et al., 2015) and B19 between 699 and 1001 CE and annual-resolved non-sea-salt sulfur concentrations from a four ice-core stack (NEEM-2011-S1, NGRIP1, TUNU2013, B19) between 1731 and 1996 CE including volcanic samples and with volcanic samples replaced by a 11-year running median. Volcanic event detection is based a 91-year running median (RM) was used on the annually averaged nssS records on periods unaffected by strong changes in volcanic background emissions to estimate the natural background sulfate levels; a Median of Absolute Deviation (MAD), calculated from the RM, was used for volcanic peak detection over the background period. Between 700 and 1000 CE sulfur peaks were considered volcanic if they passed an upper threshold (K=3, estimated as RM plus 3* MAD). The duration of the event was determined when it passed the lower threshold (K=1, estimated as the RM plus 1 * MAD). These upper and lower thresholds were selected by validation on well-known historic eruptions; volcanic peaks were then removed to calculate the non-volcanic background (S RRMi). To further calculate the amount of sulfate deposited, S RRMi was subtracted from the average annual nss-S and then multiplied by the accumulation rate of the drill site; finally, volcanic flux was calculated for each event by summing the sulfate deposited across the total duration of the event. All ice cores are presented on the NS1-2011 chronology (Sigl et al., 2015) except for NGRIP2 which was on the NGRIP2-DRI chronology (McConnell et al., 2018).

Description: Sulfate concentration and triple sulfur isotope (32S, 33S, 34S) data measured in TUNU2013 ice-core samples and calculated background-corrected isotope composition (Gabriel et al., in review). S-isotope analyses were made on 65 discrete samples (cross-sections of 6 cm2) cut from archived ice-core sections from TUNU2013, including prior background and full acid deposition lasting over 12 years. The sample resolution over the entire acid deposition event is 3 cm corresponding to a nominal 3-to-4-month age resolution. Sulfate concentration was measured by ion chromatography on the discrete samples, and the sulfate was purified from the melted ice using anion exchange columns. Triple sulfur isotopes (32S, 33S, and 34S) were measured on the samples using a Neptune Plus multi-collector inductively-coupled mass spectrometer (MC-ICP-MS) at the St Andrews Isotope Geochemistry Lab (STAiG lab) (Burke et al., 2019; Burke et al., 2023) and are reported as δ34S and D33S relative to Vienna-Canyon Diablo Troilite (V-CDT), where δxS =(xS/32S)sample/(xS/32S)V-CDT−1. A sample is considered to have a mass-independent fractionation signature if it has a nonzero value of D33S = δ33S -((δ34S + 1)^0.515 − 1), outside of 2σ uncertainty. Full procedural blanks and an in-house secondary standard (Switzer Falls) were processed alongside samples. All data was blank corrected for the process blanks, and uncertainties were propagated with Monte Carlo simulations. The isotopic composition of the volcanic sulfate (δ34Svolc and D33Svolc) was calculated using isotope mass balance and the concentration and isotopic composition of background ice from TUNU2013 taken prior and after the volcanic peaks in sulfate. Data is shown on the NS1-2011 chronology (Sigl et al., 2015). Isotopic composition of the volcanic sulfate is only provided for samples with more than 65% volcanic sulfate following Burke et al. (2019).

Description: We present continuous records of 1 cm resolved sodium, sulfur, non-sea-salt sulfur, size-resolved insoluble particle concentrations and liquid conductivity using a Continuous Flow Analysis (CFA) system (McConnell et al., 2017) from the Greenland Ice Sheet Project Two (GISP2; 72.97°N, 38.80°W) ice core and estimated volcanic sulfate mass depositions for the depth interval 2635-2638 m (equivalent to an age of c. 80 ka BP on GICC05modelext (Seierstad et al., 2014) and 79.5 ka BP on AICC2012 (Veres et al., 2013). The reconstruction is based on sulfur measurements employing high-resolution continuous flow analysis coupled to inductively coupled plasma mass spectrometry performed at the Desert Research Institute (Reno, NV, USA) under (class 100) cleanroom conditions. Volcanic eruptions are detected when annual sulfur concentrations exceeded the background concentrations + 4 times the median of the absolute deviation. Background concentrations are estimated using a 101-point running median. Volcanic sulfate deposition rates are calculated by subtracting the background concentrations from total sulfate equivalent (i.e. sulfur x 3) concentrations using thinning corrected estimates of mean ice accumulation rates at the ice-core site.