Magnitude, frequency and climate forcing of global volcanism during the last glacial period as seen in Greenland and Antarctic ice cores (60–9 ka)

Abstract

Abstract. Large volcanic eruptions occurring in the last glacial period can be detected by their accompanying sulfuric acid deposition in continuous ice cores. Here we employ continuous sulfate and sulfur records from three Greenland and three Antarctic ice cores to estimate the emission strength, the frequency and the climatic forcing of large volcanic eruptions that occurred during the second half of the last glacial period and the early Holocene, 60–9 kyr before 2000 CE (b2k). Over most of the investigated interval the ice cores are synchronized, making it possible to distinguish large eruptions with a global sulfate distribution from eruptions detectable in one hemisphere only. Due to limited data resolution and large variability in the sulfate background signal, particularly in the Greenland glacial climate, we only list Greenland sulfate depositions larger than 20 kg km−2 and Antarctic sulfate depositions larger than 10 kg km−2. With those restrictions, we identify 1113 volcanic eruptions in Greenland and 737 eruptions in Antarctica within the 51 kyr period – for which the sulfate deposition of 85 eruptions is found at both poles (bipolar eruptions). Based on the ratio of Greenland and Antarctic sulfate deposition, we estimate the latitudinal band of the bipolar eruptions and assess their approximate climatic forcing based on established methods. A total of 25 of the identified bipolar eruptions are larger than any volcanic eruption occurring in the last 2500 years, and 69 eruptions are estimated to have larger sulfur emission strengths than the Tambora, Indonesia, eruption (1815 CE). Throughout the investigated period, the frequency of volcanic eruptions is rather constant and comparable to that of recent times. During the deglacial period (16–9 ka b2k), however, there is a notable increase in the frequency of volcanic events recorded in Greenland and an obvious increase in the fraction of very large eruptions. For Antarctica, the deglacial period cannot be distinguished from other periods. This confirms the suggestion that the isostatic unloading of the Northern Hemisphere (NH) ice sheets may be related to the enhanced NH volcanic activity. Our ice-core-based volcanic sulfate records provide the atmospheric sulfate burden and estimates of climate forcing for further research on climate impact and understanding the mechanism of the Earth system.

Frequency of large volcanic eruptions over the past 200,000 years

“…4); this gives an average of 3.4 per millennium. Although our method is identical in concept, we calculate rather more peaks greater than 20 mg m -2 (2.87/ka vs 2.21/kyr) for the period 9-60 ka than that estimated for EDC by previous work (Lin et al, 2022). This difference seems to arise because our method calculates higher integrals for smaller peaks, suggesting that the difference is related to the way that the background is calculated and/or the way that we deal with the width of each peak.…”

“…For Antarctica, using methods similar to those we describe later, the authors (Lin et al, 2022) found no significant change in eruption rate across the 60 kyr period.…”

“…While this provides no direct information on the location and magnitude of each eruption, it can be used to log eruptions relevant for climate forcing (Gao et al, 2008;Sigl et al, 2015). There have been only limited investigations (Castellano et al, 2005;Castellano et al, 2004;Cole-Dai et al, 2021;Lin et al, 2022) to estimate volcanic eruption occurrence from ice core data beyond the last 2500 years.…”

“…Despite these problems two recent papers (Cole-Dai et al, 2021;Lin et al, 2022) have attempted to assess eruption frequency.…”

“…One (Cole-Dai et al, 2021) examined the number of eruptions recorded in the WAIS Divide core over the last 11 kyr, observing variability but no trend in eruption rate. A second (Lin et al, 2022) assessed eruption frequencies recorded in both Greenland and Antarctica over the period from 9-60 kyr ago, and compared them with the rates in the last 2 kyr. For Greenland they found relatively constant rates of eruption through time, but with a small increase in frequency of recorded eruptions across the deglaciation (21-9 ka).…”