Holocene productivity changes off Adélie Land (East Antarctica)

Abstract

[1] This study presents the first high-resolution multiproxy investigation of primary productivity (PP) during the Holocene from the Antarctic continental margins. Micropaleontological and geochemical data from the sediment core MD03-2601, associated to sea ice model outputs, give unprecedented insights into the biological pump of the Antarctic coastal area off Adélie Land in response to climatic changes. Plurimillennial and millennial changes of PP are observed in the study area in response to changes in nutrient availability, stratification, and growing season duration, which are linked to sea ice, upwelling, wind, and glacier dynamics. The precessional cycle seems to be responsible in the PP long-term variations, while forcing factors involved at the millennial timescale remain more enigmatic. Our results emphasize enhanced biological pump during warmer and windier Holocene phases because of a longer growing season and greater nutrient input. Antarctic coastal and continental shelf zones may therefore represent a more intense carbon sink in the future.

Penguin tissue as a proxy for relative krill abundance in East Antarctica during the Holocene

“…Variation of the inferred relative krill abundance (represented by the inverse of δ 15 N values in penguin tissues) was found to be in accordance with previously reconstructed episodes of climate change during the Holocene in East Antarctic323334. That is, periods with high krill abundance (lower δ 15 N values) correspond to cold climates3233, whereas periods with low krill abundance (higher δ 15 N values) correspond to warm climates3234.…”

“…Here, we determined the episodic warm periods (7500–6300 yr BP and 4800–2200 yr BP) and cold periods (8500–7600 yr BP and 6300–5700 yr BP) according to previously reconstructed climate change during the Holocene in East Antarctic based on ice cores32 and marine sediment cores3334. Using information of warm/cold periods provided in Table 1, we were able to compare δ 15 N values in cold periods against those in warm periods.…”

“…That is, periods with high krill abundance (lower δ 15 N values) correspond to cold climates3233, whereas periods with low krill abundance (higher δ 15 N values) correspond to warm climates3234. Krill is a stenothermal, cold-water planktonic species, and is very sensitive to natural climate changes.…”

Sea ice diatom contributions to Holocene nutrient utilization in East Antarctica

“…[] and Denis et al . [], based on high‐resolution changes in dominant diatom assemblages and geochemical proxies over the course of the Holocene: the early Holocene (circa 11,000 to 7800 cal years B.P. ), the mid‐Holocene Hypsithermal (circa 7800 to circa 3500 cal years B.P.…”

“…The data presented in this paper add to published work on sea‐surface temperature, sea ice cover, and productivity changes [ Crosta et al ., , ; Denis et al ., , , , ]. The main driver for the addition of δ 30 Si diat and δ 13 C diat analyses is to quantify specific nutrient utilization by diatoms (which dominate productivity in this region) over the Holocene.…”