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: 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: Based on a set of continuous sulfate records from a suite of ice cores from Greenland and Antarctica, the HolVol v.1.0 database includes estimates of the magnitudes and approximate source latitudes of major volcanic stratospheric sulfur injection (VSSI) events for the Holocene (from 9500 BCE or 11500 year BP to 1900 CE), constituting an extension of the previous record by 7000 years. The database incorporates new-generation ice-core aerosol records with sub-annual temporal resolution and demonstrated sub-decadal dating accuracy and precision. By tightly aligning and stacking the ice-core records on the WD2014 chronology from Antarctica we resolve long-standing previous inconsistencies in the dating of ancient volcanic eruptions that arise from biased (i.e. dated too old) ice-core chronologies over the Holocene for Greenland. A long-term latitudinally and monthly resolved stratospheric aerosol optical depth (SAOD) time series is reconstructed from the HolVol VSSI estimates, representing the first such reconstruction Holocene-scale reconstruction constrained by Greenland and Antarctica ice cores. These new long-term reconstructions of past VSSI and SAOD variability confirm evidence from regional volcanic eruption chronologies (e.g., from Iceland) in showing that the early Holocene (9500-7000 BCE) experienced a higher number of volcanic eruptions (+16%) and cumulative VSSI (+86%) compared to the past 2,500 years. This increase is coinciding with then rapidly retreating ice sheets during deglaciation, providing context for potential future increases of volcanic activity in regions under projected glacier melting in the 21st century.

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 continuous records of 1 cm resolved sulfate concentrations, insoluble particle number and mass concentration, and liquid conductivity using a Continuous Flow Analysis (CFA) system (Bigler et al., 2002; Bigler et al., 2011; Erhardt et al., 2022) from the North Greenland Ice Core Project (NGRIP; 75.10°N, 42.33°W; 2941 m a.s.l.) and estimated volcanic sulfate mass depositions for the time period 79.14 and 80.48 ka BP on the GICC05modelext chronology, transferred to the AICC2012 chronology (Veres et al., 2013; Seierstad et al., 2014) using a common volcanic marker in EPICA Dome C ice core dated 79.51 ka BP. The reconstruction is based on sulfate measurements employing high-resolution continuous flow analysis. Volcanic eruptions are detected when annual sulfate concentrations exceeded the background concentrations + 4 times the median of the absolute deviation. Background concentrations are estimated using a 181-point running median. Volcanic sulfate deposition rates are calculated by subtracting the background concentrations from total sulfate concentrations using thinning corrected estimates of mean ice accumulation rates at the ice-core site.

Description: The D4 ice core was recovered in 2003 from a high elevation, cold site in the dry snow region of the Greenland ice sheet (71.4°N, 43.9°W, 2730 m asl, 41 cm water equivalent per year annual accumulation rate). Initial collection and previous analyses of the core have been reported earlier (e.g., McConnell et al., 2007). New longitudinal samples of ~32 by ~32 mm were cut (D4i) from contiguous sections of the remaining D4 core archived in a commercial storage facility in Reno. The samples from near and below the pore close-off depth (66-145 m depth; dating 1733-1900 CE) were analyzed continuously using a state-of-the-art ice core analytical system. https://icecores.org/inventory/d4 . Mean monthly D4i non-sea-salt sulfur concentrations corrected for sea-salt sulfur contribution based on [Na], assuming a S/Na mass ratio of seawater of 0.084 [Bowen, 1979]. Estimated mean monthly D4i median pre-industrial (1733-1875 CE) sulfur background concentrations after excluding volcanic events identified as monthly values exceeding the median concentrations plus two times the interquartile range (Q3 minus Q1). D4i Excess-sulfur concentrations defined as non-sea-salt sulfur concentrations minus sulfur background concentrations; negative values set to 0; using monthly resolved excess-sulfur, we estimated long-term trends with a 61-yr running median (RM); we attributed a volcanic origin to values exceeding a threshold of the RM + 4 x MAD (median of absolute deviation); we multiplied each monthly excess-sulfur concentration value exceeding the detection treshold with 0.41 water equivalent per year / 12 (i.e., assuming constant snowfall rate throughout the year) to derive monthly volcanic sulfate deposition at the D4 site.