East Antarctic ice core record reveals a dramatic rise in anthropogenic copper emissions since ~ 1985

Abstract

Antarctic ice cores provide past atmospheric composition beyond the timeframe of the instrumental records. Here, we examine the record of copper (Cu), a trace metal contaminant, from an ice core record spanning the past ~ 200 years (1809–2012 CE) from the coastal Dronning Maud Land (cDML), East Antarctica (71.5° S, 10.25° E). We observed two-phase variability in Cu flux, first with no discernible trend (slope =  − 0.0001, p = 0.27), and marked by a few high flux periods related to El Niño Southern Oscillations (ENSO) events during 1809–1942 (average = 0.05 µg cm−² a−¹), and second phase with an exponentially increasing trend that started around 1943 (R² = 0.424, average = 0.09 µg cm−² a−¹), resulting in the doubling of Cu deposition after 1985 (average = 0.14 µg cm−² a−¹). Our study reveals that the dramatic increase of Cu deposition since ~ 1985 can be attributed to the combined role of 42-fold increase in Cu production from Chilean Cu mines and favorable atmospheric transport by a deepened low-pressure anomaly and stronger westerlies associated with the positive phase of the Southern Annular Mode (SAM). A comparable trend was observed for antimony (Sb), a trace element often associated with primary copper minerals, further supporting the attribution of elevated Cu deposition at the core site to historical mining activities. Our investigation on the Cu flux record revealed strong linkages with climate modes such as SAM and ENSO in controlling the variability of the Cu deposition flux. Further, examining the specific peaks and dips in the Cu flux record during 1985–2012, peak years showed an average wind intensification of 0.45–1.05 ms−¹ compared to dip years, which contributed to the doubling of Cu deposition over the region. Considering this increasing trend in Cu deposition in this region, elevated copper levels may pose a long-term risk to phytoplankton growth and primary productivity in the Southern Ocean due to potential Cu toxicity.