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- Title
Duration of Greenland Stadial 22 and ice-gas Δage from counting of annual layers in Greenland NGRIP ice core.
- Authors
Vallelonga, P.; Bertagna, G.; Blunier, T.; Kjær, H. A.; Popp, T. J.; Rasmussen, S. O.; Steffensen, J. P.; Stowasser, C.; Svensson, A. S.; Warming, E.; Winstrup, M.; Bigler, M.; Kipfstuhl, S.
- Abstract
The NorthGRIP ice core chronology GICC05modelext is composed of the annual-layer counted GICC05 chronology to 60 kyr before 2000 AD (b2k), and an ice flow model dating the deepest part of the ice core to 123 kyr b2k. Determination of annual strata in ice beyond 60 kyr b2k has been challenged by the thinning of annual layers to <1 cm and the appearance of microfolds in some early glacial strata. We report high-resolution measurements of a 50 m section of the NorthGRIP ice core and corresponding annual layer thicknesses, constraining the duration of the Greenland Stadial (GS-22) between Greenland Interstadials (GIs) 21 and 22 which occurred between approximately 89 (end of GI-22) and 83 kyr b2k (onset of GI-21) depending on the chronology used. Multiple analytes (insoluble dust particles, electrolytic conductivity, ammonium and sodium) were determined in annual layers of ice often thinner than 1 cm. From annual layer counting, we find that GS-22 lasted 2894 ± 198 yr and was followed by a GI-21 pre-cursor event lasting 350 ± 19 yr. Our layer-based counting agrees with the duration of GS-22 determined from the NALPS speleothem record (3250 ± 526 yr) but not with that of the GICC05modelext chronology (2620 yr). These results show that GICC05modelext overestimates accumulation and/or underestimates thinning in this early part of the last glacial period. We also revise the NorthGRIP ice depth-gas depth (5.67 ± 0.18 m) and ice age-gas age (550 ± 52 yr) differences at the warming onset of GI-21, observing that δ15N increases before CH4 concentration by no more than a few decades.
- Subjects
GREENLAND; ICE cores; CHRONOLOGY; MATHEMATICAL models; CLIMATE change; ELECTRIC conductivity; SPELEOTHEMS
- Publication
Climate of the Past Discussions, 2012, Vol 8, Issue 4, p2583
- ISSN
1814-9324
- Publication type
Article
- DOI
10.5194/cpd-8-2583-2012