Signal and noise in four ice-core records from the Agassiz Ice Cap,Ellesmere Island,Canada: details of the last millennium for stable isotopes,melt and solid conductivity

Abstract

Four ice cores and two deep pit/auger sequences from the top of the Agassiz Ice Cap have been variously analysed for δ(O¹⁸), ECM (solid conductivity) and ice melt-layer stratigraphy. The high- resolution data are presented on time scales covering about the last 1000 years. The 8 time series are compared and the noise examined in terms of snow-drifting and wind-scouring of winter snow from the higher exposed parts of flow lines. The highly scoured 8 records reflect a mixture of summer-biased conditions and the amount of winter-scoured snow. Sites away from the ridges and domes are not scoured. The signal part of the scoured and unscoured sites is obtained by stacking (averaging normalized series). The stacked unscoured series of 8 and accumulation are compared to similar stacked series from central Greenland for the last century of annual averages. The comparison is surprisingly good suggesting that at these resolutions low-noise 8 series have some coherence over fairly large distances. The percentage melt series are presented and compared to those from the Devon Island Ice Cap.

Keywords

Ice core stable isotopes 18O ice melt solid conductivity ECM volcanic acid Agassiz Ice Cap Ellesmere Island Canada

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References

Barrie, L.A. , Fisher, D.A. and Koerner, R.M. 1985: Twentieth century trends in Arctic air pollution revealed in conductivity and acidity observations in snow and ice in the Canadian high Arctic. Atmospheric Environment 19, 2055-63.

Briffa, K.R. and Jones, P.D. 1993: Global surface air temperature variations during the twentieth century: part 2, implications for large-scale high-frequency palaeoclimatic studies. The Holocene 3(1), 77-88.

Clausen, H.B. , Gundestrup, N. , Johnsen, J.S. , Bindschadler, R. and Zwally, J. 1988: Glaciological investigations in the Crete area central Greenland: a search for a new deep-drilling site. Annals of Glaciology 10, 10-15.

Dansgård, W. , Johnsen, SJ , Clausen, H.B. and Gundestrup, N. 1973: Stable isotope glaciology. Meddelelser om Grønland 197(2), 1-53.

Fisher, D.A. 1977: Melt feature stratigraphy, oxygen isotope ratio and climate over 800 years, from the Devon ice cap cores. Internal Report of Polar Continental Shelf Project, Energy Mines and Resources, Canada.

— 1991: A zonally-averaged stable-isotope model coupled to a regional variable elevation stable isotope model. Annals of Glaciology 14, 65-71.

— 1992a: Stable isotope simulations using a regional stable isotope model coupled to a zonally averaged global model. Cold Regions Science and Technology 21, 61∼77.

— 1992b: Possible ice-core evidence for a fresh melt water cap over the Atlantic Ocean in the early Holocene. In Bard, E. and Broecker, W.S. , editors, The last deglaciation: absolute and radiocarbon chronologies , Berlin: Springer-Verlag. Nato ASI series, Volume 12, 267-93.

Fisher, D.A. and Koerner, R.M. 1983: Ice-core study: a climatic link between the past, present and future. Syllogeus 49, 50—69.

10.

— 1988: The effects of wind on δ(18O) and accumulation give an inferred record of seasonal 8 amplitude from the Agassiz ice cap, Ellesmere Island, Canada. Annals of Glaciology 10, 34-37.

11.

Fisher, D.A. , Koerner, R.M. , Patersen, W.S.B. , Dansgård, W. , Gundestrup, N. and Reeh, N. 1983: Effect of wind scouring on climatic records from ice-core oxygen-isotope profiles. Nature 301(5897), 205-209.

12.

Fisher, D.A. , Reeh, N. and Clausen, H.B. 1985: Stratigraphic noise in time series derived from ice cores . Annals of Glaciology 7, 76-83.

13.

Hammer, C.U. 1984: Traces of Icelandic eruptions in the Greenland ice sheet . Jökull 34, 51-65.

14.

Hammer, C.U. , Clausen, H.B. , Dansgård, W. , Gundestrup, N. , Johnsen, SJ and Reeh, N. 1978: Dating of Greenland ice cores by flow models, isotopes volcanic debris and continental dust. Journal of Glaciology 20(82), 3-26.

15.

Hammer, C.U. , Clausen, H.B. and Dansgård, W. 1980: Greenland ice sheet evidence of post glacial volcanism and its climatic impact. Nature 288(5788), 230-35.

16.

Joussaume, S. , Jouzel, J. and Sadourny, R. 1984: A general circulation model of water isotope cycles in the atmosphere. Nature 311 (5981 ), 24-29.

17.

Jouzel, J. , Russell, G.L. , Souzzo, RJ , Koster, R.D. , White, J.W.C. and Broecker, W.S. 1987: Simulations of the HDO and H2 (18O) atmospheric cycles using the NASA GISS general circulation model

18.

the seasonal cycle for present day conditions. Journal of Geophysical Research 92(D12) 14739-60.

19.

Koerner, R.M. 1977: Devon Island ice cap; core stratigraphy and palioclimate . Science 196, 15-18.

20.

Koerner, R.M. and Fisher, D.A. 1990: A record of Holocene summer climate from a Canadian high-Arctic ice core. Nature 343(6259), 630-31.

21.

Langway, C.C. Jr., Clausen, H.B. and Hammer, C.U. 1988: An interhemispheric volcanic time-marker in ice cores from Greenland and Antarctica. Annals of Glaciology 10, 1-7.

22.

Wwd 1990: World weather disc version 2.0. Seattle: WeatherDisc Associates Inc., standard CDROM.