posted on 2021-08-23, 05:04authored byJu Hyeon Lee, Sae Yun Kwon, Hoin Lee, Seung-Il Nam, Jung-Hyun Kim, Young Ji Joo, Kwangchul Jang, Haryun Kim, Runsheng Yin
Despite the large climatic fluctuations
in the Arctic over the
Holocene, the dominant mercury (Hg) sources and the potential changes
in Hg sources associated with the climate remain unclear. Here, we
use Hg isotopes to reconstruct changes in Hg sources and processes
in two Svalbard fjord sediment cores spanning the Holocene. The Hg
isotope ratios of the fjord sediment cores are similar to bedrock
and Hg bound to terrestrial total organic carbon (TOC) but different
from other sediment cores influenced by atmospheric Hg drawdowns via
the sinking of marine particulate organic matter. The absence of significant
Hg and TOC relationships indicates that bedrock erosion caused by
glacier dynamics is the major Hg source to the fjord sediment rather
than those bound to marine and terrestrial TOC. Measurable shifts
in Hg sources are observed at regional cooling (4.3 ka) and during
the Medieval Warm Period in the late Holocene. The negative shift
in δ202Hg (by −0.5‰) at 4.3 ka from
baseline (∼10 ka) is consistent with the rapid increase in
glacier-mediated physical and chemical erosions of bedrock. The significant
positive shifts in δ202Hg (by 0.5‰) in the
late Holocene are explained by enhanced input of atmospheric Hg and
its drawdown via the sinking of marine particulate organic matter
and some anthropogenic influence, which suppressed the positive Δ199Hg and Δ200Hg shifts. This study suggests
that Hg isotope ratios measured in sedimentary archives can be used
to decipher climate and other local to global changes modifying Hg
sources in the Arctic.