@inproceedings{fdi:010064308,
  title = {{S}ea ice, biological production and nutrient cycling reconstructed at an unprecedented time resolution in the {A}d{\'e}lie {B}asin, {E}ast {A}ntarctica, for the last 2,000 years : poster},
  author = {{E}tourneau, {J}. and {C}ampagne, {P}. and {J}imenez, {F}. and {D}jouraev, {I}rina and {O}gawa, {N}. and {E}scutia, {C}. and {D}unbar, {R}. and {O}hkouchi, {N}. and {C}rosta, {X}. and {M}ass{\'e}, {G}.},
  editor = {},
  language = {{ENG}},
  abstract = {{A}ntarctic sea ice impacts on the ocean-atmosphere heat and gas fluxes, the formation of deep and intermediate waters, the nutrient distribution and primary productivity, the so-called ‘biological carbon pump’, one of the most active in the global ocean. {I}n this study, we explore the link between sea ice dynamic, biological production and nutrient cycling during the late {H}olocene (the last 2,000 yrs) in the {A}d{\'e}lie {B}asin, {E}ast {A}ntarctica, from the well-dated sediments of the {O}cean {D}rilling {P}rogram ({ODP}) {S}ite {U}1357. {T}his archive, composed from ~32 meters of seasonal to annual laminated diatomaceous sequences, allows reconstructions at an unprecedented time resolution (5-10 yrs). {O}ur study combines records of diatom census counts and diatom-specific biomarkers (a ratio ({D}/{T}) of di- and tri-unsaturated {H}ighly {B}ranched {I}soprenoid lipids ({HBI})) as indicators of sea ice and biological production changes, {XRF} data as markers for terrigenous inputs and bulk nitrogen isotopes (d15{N}) and d15{N} on chlorins as proxies for reconstructing nitrogen cycle. {T}he diatom and {HBI} records reveal five distinct periods. {F}rom 0 to 350 yrs {AD}, decreasing occurrences of sea ice-related diatom species (e.g. {F}ragilariopsis curta + {F}. cylindrus) together with low {D}/{T} values and increasing open ocean diatom species (large centrics, {C}haetoceros {R}esting {S}pores ({CRS})) document a progressive decline of sea ice presence during the year (>9 months per year) with spring melting occurring earlier in the year and autumn sea ice formation appearing later. {I}n contrast, between 350 and 750 yrs {AD}, high production of open ocean diatom species and low low {D}/{T} values and sea ice related species indicate a short duration of sea ice cover (<~8 months per year). {F}rom 750 to 1400 yrs {AD}, a prolonged seasonal sea ice (>~10 months per year) is illustrated by a pronounced increase of sea ice-associated diatom species and high {D}/{T} values. {B}etween ~1400 and 1850 yrs {AD}, seasonal sea ice strongly declines (<~7 months per year) as a result of early spring melting (increasing {CRS} production) and late autumn waxing (high occurrences of {T}halassiosira antarctica). {L}onger growing seasons promoted a substantial development of phytoplankton communities (especially large centric diatoms) that conducted to lower {D}/{T} values. {C}onsistent with diatom and {HBI} reconstructions, {XRF} data show higher {F}e/{A}l and {Z}r/{A}l ratios values during inferred warmer periods and lower ratio values during inferred cooler and icier periods, thus supporting a strong impact of the sea ice seasonal cycle on glacial runoffs. {T}he link between sea ice conditions, biological production and nutrient cycling is still being explored and we will discuss its relationship by combining all the cited records cited above with the d15{N} records that we are currently generated. {B}ased on our results, we find that sea ice dynamic and associated diatom production in the {A}d{\'e}lie {B}asin revealed an opposite climatic trend than that identified in the {N}orthern {H}emisphere for the last 2000 years. {T}he '{L}ittle {I}ce {A}ge' (1400-1850 yrs {AD}) or the '{D}ark {A}ges' (400-750 yrs {AD}) corresponded to warmer climate conditions in the {A}d{\'e}lie {B}asin, while the '{R}oman {W}arm {P}eriod' (0-350 yrs {AD}) or the '{M}edieval {W}arm {P}eriod' (900-1200 yrs {AD}) were associated to colder conditions. {W}e therefore emphasize that {N}orthern and {S}outhern {H}emisphere climate evolved in anti-phase seesaw pattern during the late {H}olocene.},
  keywords = {{MILIEU} {GLACIAIRE} ; {INTERACTION} {OCEAN} {ATMOSPHERE} ; {PALEOCLIMAT} ; {HOLOCENE} ; {PRODUCTION} {PRIMAIRE} ; {SUBSTANCE} {NUTRITIVE} ; {CYCLE} {BIOGEOCHIMIQUE} ; {AZOTE} ; {DIATOMEE} ; {VARIATION} {SECULAIRE} ; {VARIATION} {SAISONNIERE} ; {CALOTTE} {GLACIAIRE} ; {PETIT} {AGE} {GLACIAIRE} ; {OCEAN} {ANTARCTIQUE} ; {TERRE} {ADELIE}},
  numero = {},
  pages = {58},
  booktitle = {{T}he past : a compass for future earth},
  year = {2013},
  URL = {https://www.documentation.ird.fr/hor/fdi:010064308},
}