The Northern Hemisphere experienced dramatic changes during the last glacial, featuring vast ice sheets and abrupt climate events, while high northern latitudes during the last interglacial (Eemian) were warmer than today. Here we use high-resolution aerosol records from the Greenland NEEM ice core to reconstruct the environmental alterations in aerosol source regions accompanying these changes. Separating source and transport effects, we find strongly reduced terrestrial biogenic emissions during glacial times reflecting net loss of vegetated area in North America. Rapid climate changes during the glacial have little effect on terrestrial biogenic aerosol emissions. A strong increase in terrestrial dust emissions during the coldest intervals indicates higher aridity and dust storm activity in East Asian deserts. Glacial sea salt aerosol emissions in the North Atlantic region increase only moderately (50%), likely due to sea ice expansion. Lower aerosol concentrations in Eemian ice compared to the Holocene are mainly due to shortened atmospheric residence time, while emissions changed little.

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The continuous growth of atmospheric nitrous oxide (N 2 O) is of concern for its potential role in global warming and future stratospheric ozone destruction. Climate feedbacks that enhance N 2 O emissions in response to global warming are not well understood, and past records of N 2 O from ice cores are not sufficiently well resolved to examine the underlying climate-N 2 O feedbacks on societally relevant time scales. Here, we present a new high-resolution and high-precision N 2 O reconstruction obtained from the Greenland NEEM (North Greenland Eemian Ice Drilling) and the Antarctic Styx Glacier ice cores. Covering the N 2 O history of the past two millennia, our reconstruction shows a centennial-scale variability of~10 ppb. A pronounced minimum at~600 CE coincides with the reorganizations of tropical hydroclimate and ocean productivity changes. Comparisons with proxy records suggest association of centennial-to millennial-scale variations in N 2 O with changes in tropical and subtropical land hydrology and marine productivity. Plain Language Summary Nitrous oxide (N 2 O) is a greenhouse and ozone-depleting gas. The growing level of N 2 O in the atmosphere is of global concern, and records of past N 2 O variations can provide an important context for understanding the links between N 2 O and climate change. In this study, we report new, high-quality N 2 O records covering the last two millennia using ice cores obtained from Greenland and Antarctica. Our N 2 O records show rapid centennial-scale changes in atmospheric N 2 O and confirm a pronounced minimum near 600 CE. Comparison with climate records suggests that hydroclimate change on land and changes in marine productivity contribute to centennial-to millennial-scale N 2 O variations.

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The melting system installed in a freezer under a clean booth (class 100) and the ratios of signal intensity (SIR) of elements in blank artificial ice core to the elements in system blank from three zones of melting head during melting procedures. The ratio with one standard deviation is represented (n = 3).