English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The 17O excess(Δ17O = δ17O−0.52 × δ18O) ofsulfate and nitrate reflects the relative importance of their differentproduction pathways in the atmosphere. A new record of sulfate and nitrateΔ17O spanning the last 2400 years from the West Antarctic Ice SheetDivide ice core project shows significant changes in both sulfate and nitrateΔ17O in the most recent 200 years, indicating changes in theirformation pathways. The sulfate Δ17O record exhibits a1.1 ‰ increase in the early 19th century from(2.4 ± 0.2) ‰ to (3.5 ± 0.2) ‰, which suggests thatan additional 12–18% of sulfate formation occurs via aqueous-phaseproduction by O3, relative to that in the gas phase. NitrateΔ17O gradually decreases over the whole record, with a more rapiddecrease between the mid-19th century and the present day of 5.6 ‰,indicating an increasing importance of RO2 in NOx cyclingbetween the mid-19th century and the present day in the mid- to high-latitudeSouthern Hemisphere. The former has implications for the climate impacts ofsulfate aerosol, while the latter has implications for the tropospheric O3production rate in remote low-NOx environments. Using other icecore observations, we rule out drivers for these changes other thanvariability in extratropical oxidant (OH, O3, RO2, H2O2, andreactive halogens) concentrations. However, assuming OH, H2O2, andO3 are the main oxidants contributing to sulfate formation, Monte Carlobox model simulations require a large (≥ 260%) increase in theO3 / OH mole fraction ratio over the Southern Ocean in the early 19thcentury to match the sulfate Δ17O record. This unlikely scenariopoints to a~deficiency in our understanding of sulfur chemistry and suggestsother oxidants may play an important role in sulfate formation in the mid- tohigh-latitude marine boundary layer. The observed decrease in nitrateΔ17O since the mid-19th century is most likely due to an increasedimportance of RO2 over O3 in NOx cycling and can beexplained by a 60–90% decrease in the O3 / RO2 mole fractionratio in the extratropical Southern Hemisphere NOx-sourceregions

atmospheric chemistry and physics

WAIS Divide ice core suggests sustained changes in the atmospheric formation pathways of sulfate and nitrate since the 19th century in the extratropical Southern Hemisphere