Canadian forest fires, Icelandic volcanoes and increased local dust observed in six shallow Greenland firn cores

Abstract

Abstract. Greenland ice cores provide information about past climate. Few impurity records covering the past 2 decades exist from Greenland. Here we present results from six firn cores obtained during a 426 km long northern Greenland traverse made in 2015 between the NEEM and the EGRIP deep-drilling stations situated on the western side and eastern side of the Greenland ice sheet, respectively. The cores (9 to 14 m long) are analyzed for chemical impurities and cover time spans of 18 to 53 years (±3 years) depending on local snow accumulation that decreases from west to east. The high temporal resolution allows for annual layers and seasons to be resolved. Insoluble dust, ammonium, and calcium concentrations in the six firn cores overlap, and the seasonal cycles are also similar in timing and magnitude across sites, while peroxide (H2O2) and conductivity both have spatial variations, H2O2 driven by the accumulation pattern, and conductivity likely influenced by sea salt. Overall, we determine a rather constant dust flux over the period, but in the data from recent years (1998–2015) we identify an increase in large dust particles that we ascribe to an activation of local Greenland sources. We observe an expected increase in acidity and conductivity in the mid-1970s as a result of anthropogenic emissions, followed by a decrease due to mitigation. Several volcanic horizons identified in the conductivity and acidity records can be associated with eruptions in Iceland and in the Barents Sea region. From a composite ammonium record we obtain a robust forest fire proxy associated primarily with Canadian forest fires (R=0.49).

Diurnal and seasonal source‐proximal dust concentrations in complex terrain, West Greenland

“…Several studies have recorded the occurrence of dust on the surface of snow and ice on the GrIS and traced it mineralogically or sedimentologically to local Greenland dust sources (e.g. Bøggild et al, 2010; Kjær et al, 2022; Wientjes et al, 2011). In the cryosphere, dust deposits can contribute to the development of cryoconite holes that reduce albedo and can increase ice melt rates (Bøggild et al, 2010).…”

“…Dust derived from ice‐free Greenland provides nutrients and sediments to terrestrial and cryospheric ecosystems (Anderson et al, 2017; McCutcheon et al, 2021) and is estimated to contribute approximately 1 Tg year −1 to the global dust load (Groot Zwaaftink et al, 2016). In addition, recent analyses of lake, firn and ice core records suggest dust emission from Greenland has increased over the past 20 years due to increased sediment availability (Amino et al, 2021; Kjær et al, 2022). Within this paper, we consider first the overall annual environmental conditions during 2018 and 2019 when the data were collected, in order to situate the results in the longer‐term context of a rapidly changing Arctic.…”

An annually resolved chronology for the Mount Brown South ice cores, East Antarctica

“…We undertook sequential inter-laboratory comparisons of discrete and CFA derived isotopes at the three isotope-capable laboratories involved in this study -AAPP/IMAS in Hobart, Australia, the Australian National University in Canberra, Australia 2.4 Continuous flow analysis of trace chemistry, peroxide, dust and water stable isotopes Sample sticks (34 x 34 mm) for continuous flow analysis (CFA) sectioned from the MBS Main core and the Charlie surface core were shipped frozen to Copenhagen to be analysed via CFA at the Niels Bohr Institute (Kaufmann et al, 2008;Bigler et al, 2011). We used a modified version of the Copenhagen CFA system (Bigler et al, 2011;Kjaer et al, 2022) during two campaigns, one which analysed the dry-drilled sections of the Main core (4-94m) and the Charlie core (CFA1: November 2018), and a second which analysed the deeper wet drilled section (95-295m) of the Main core (CFA2: November 2019).…”

“…The debubbled melt stream was split into several analytical systems, including insoluble dust (Abakus), conductivity and several simple fluorescence and absorption methods to analyse ammonium (NH 4 + ), Sodium (Na + ) and calcium (Ca 2+ ) (Bigler et al, 2011), hydrogen peroxide (H 2 O 2 ) and acid (H + ) (Kjaer et al, 2016(Kjaer et al, , 2022. Chemical signals were converted to concentrations using a linear regression produced by a set of two (H 2 O 2 and acid) or three (NH 4 + , Na + and Ca 2+ ) known standards, and the measured flow rate was used to convert the dust concentrations from counts per second to particles ml −1 .…”

Interdecadal Pacific Oscillation in Northern Greenland Dust Concentration Variability During the Last 400 Years

“…The concentration of mineral dust aerosol, a suspension of tiny soil particles in the atmosphere, is highly sensitive to climate and environmental changes. Recent studies report significant interannual to decadal variability in observed and proxy dust concentration records from Greenland (Bullard & Mockford, 2018; Kjaer et al., 2022; Nagatsuka et al., 2021), Europe (Clifford et al., 2019) or Middle‐East (Notaro et al., 2015; Yu et al., 2015) during the observational period. Strong variability in the dust concentration at longer time scales, that is, centennial to millennial, are detected in ice core records from the Arctic region (Fuhrer et al., 1999; Legrand & Mayewski, 1997; Rasmussen et al., 2014).…”