A change in seasonality in Greenland during a Dansgaard-Oeschger warming

摘要: A new sub-seasonal chemical record is presented from the North Greenland Icecore Project (NorthGRIP) ice core during onset of one longest and strongest interstadials last glacial period, Dansgaard-Oeschger event 8 (approximately 38 000 years ago). This first time that a such resolution has been achieved over several metres deep provides unique opportunity for using additional parameters to carry out accurate dating annual-layer counting. The very high-resolution data were used assess phasing various ions determine changes in seasonal strength deposition shape cycle. study shows change seasonality accompanied dramatic warming transition stadial interstadial conditions Greenland. thickness. Due exceptionally small sample size, cutting method microtome device low-volume ion chromatography was developed. section this outer- most part core; outer surfaces removed bandsaw prevent contamination drilling fluid handling. sledge then cut 2 mm samples (using passes blade succession 40 shavings), with no loss, placed clean Coulter accuvettes melting transferred into ion-chromatography auto-sampler vials analysis. Powder-free gloves protective clothing worn throughout minimize contamination. Ion (IC) five anions, chloride (Cl - ), fluoride (F methanesulphonate (MSA nitrate (NO3 ) sulphate (SO4 2- ). system reagent-free Dionex ICS-2500 column 250 mL loop. potassium hydroxide eluent generator cartridge (EGC-OH) reduce operational errors associated preparation. flow set 0.25 min -1 an isocratic elution 23 KOH. Four cations, calcium (Ca 2+ (K + sodium (Na magnesium (Mg analyzed IC-2000 3 cation equipped MSA followed 0.5 20 . sequential analyze both anions cations same vial, AS50 auto-sampler, thus minimizing volume requirements. anion are passed system. Tests made frozen ultra-pure water show blanks negligible (<5% concentration levels) all (Thomas, 2006).