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Publication and Communication

*Changes in sediment provenance and oceanography across the Denmark Strait over the last 2000 cal yr BP: An ongoing study

Authors

Andrews, John T 1 ; Alonso-García, Montserrat 2 ; Belt, Simon 3 ; Cabedo Sanz, Patricia 4 ; Darby, Dennis 5 ; Jaeger, John 6 ; Jennings, Anne E 7 ; Olafsdottir, Saedis 8


Author Affiliation

1 University of Colorado
2
University of South Florida
3
Plymouth University
4
Plymouth University
5
Old Dominion University
6
University of Florida
7
University of Colorado
8
University of Icelan

 

Event

42nd International Arctic Workshop

7-9 March 2012

Winter Park, Colorado


Abstract

The area of the Denmark Strait is a “type area” for the generally accepted climatic intervals of the last 2000 cal yr BP, including the Medieval Warm Interval (MWI) and the Little Ice Age (LIA). On the N Iceland shelf, the 2000 cal yr BP interval marks a dramatic change in benthic foraminifera, with the arctic species Elphidium clavata forma clavata, making a dramatic re-appearance. Paleoceanographic proxy data from 5 cores, resampled at 100-yr intervals, from SW, NW, and N Iceland showed a coherent response between a variety of proxies, including ice-rafted minerals, the sea ice biomarker IP25, carbonate weight%, and foraminiferal light stable isotopes (Axford et al., 2011) (Fig. 1). The 1st PCA explains 68% of the variance in the data, and is positively associated with quartz wt% and IP25, and is negatively loaded with carbonate values. Here we extend this analysis across the Denmark Strait to the more polar environment of East Greenland between Scoresby Sund and Kangerlussuaq Trough (~66°-70°N) (Fig. 2) with a multi-proxy approach including 210Pb and 137Cs dating (Jaeger), foraminifera and their light isotopes (Jennings and Olafsdottir), Fe-iron oxide provenance fingerprinting (Darby), lithic counts (Alonso-García), sea-ice biomarkers and total organic carbon content (Cabedo Sanz and Belt), and X-ray diffraction and sediment magnetic mineral composition (Andrews). Data analysis is still ongoing on several of the proxies.
Along the NW and N Iceland shelf, drift-ice is a frequent but not pervasive element in the environment, whereas in contrast, the East Greenland shelf is characterized by an extensive and pervasive cover of sea ice (~October to July ±), including landfast sea-ice, and with numerous tidewater glacier margins contributing icebergs. Kangerlussuaq Trough and Fjord, a focus of the research, is directly influenced by modified Atlantic Water, which forms an Intermediate Water mass linked to the Irminger Current (Jennings et al., 2011). We have extended our research onto the East Greenland and Iceland shelf using a number of high-resolution cores from the PO175, HU93030, JM96-, B997- and MD99- cruises. On the NW/N Iceland shelf we also present data on a series (4) of small 20-cm gravity cores collected in 1997. Chronological control is being based on AMS 14C dates, 210Pb and 137Cs (Smith et al., 2002). Three short giant gravity cores (~20 cm in length) (PO175GKC#7, -8, and –9) in the middle reaches of Kangerlussuag Trough extend back into the middle of the Little Ice Age, whereas on the inner shelf HU93030-019B and MD99-2322 can be combined to present a detailed record of environmental change over the last 2000 cal yr (Fig. 3), which can then be directly compared with data from the MD99-2263 box core (Andrews et al., 2009). Rates of sediment accumulation vary by a factor of 10 between the East Greenland (~0.2cm/yr) versus Iceland (0.02cm/yr) margins across the strait. These rates allow multi-decadal to century-scale resolution of sediment archives. The data for the last ~190 yrs in the PO175GKC cores can be compared with the historical (Schmith and Hanssen, 2003) compilation of the Storis records (ice transported around the southern tip of Greenland and north along the SW/W Greenland margin). The wealth of data that are accumulating for this cross-strait transect will be assessed to answer the following critical questions: 1) are the climate events (based on our proxies) on either side of Denmark Strait strongly correlated? 2) Can these events be strongly linked to the “standard” LIA, MWI, Dark Ages, and Roman Warm Period intervals? 3) Can we detect significant temporal variations in our proxies that deal with sediment provenance? 4) What are the associations, if any, between sediment and biological proxies?


Andrews, Darby and Jennings supported by NSF-ARC 1107761; Belt and Cabedo Sanz supported by EU FP7 2007/2013 Marie-Curie Actions Grant Agreement No. 238111; Alonso-García supported by NSF (OCE-0961670) and the Comer Science and Education Foundation (CP75).

 

 

Andrews, J.T., Belt, S.T., Olafsdottir, S., Masse, G., Vare, L., 2009, Sea ice and marine climate variability for NW Iceland/Denmark Strait over the last 2000 cal. yr BP. The Holocene, v. 19, p. 775-784.

Axford, Y., Andresen, C., Andrews, J.T., Belt, S.T., Geirsdottir, A., Masse, G., Miller, G.H., Olafsdottir, S., Vare, L.L., 2011, Do paleoclimate proxies agree? Statistical comparison of climate and sea-ice reconstructions from Icelandic marine and lake sediments, 300-1900 AD. Journal of Quaternary Science, v. 26, p. 645-656.

Jennings, A.E., Andrews, J.T., Wilson, L., 2011, Holocene environmental evolution of th SE Greenland Shelt north and south of the Denmark Strait: Irminger and East Greenland current interactions. Quaternary Science Reviews, v. 30, p. 980-998.

Schmith, T., Hanssen, C., 2003, Fram Strait ice export during the nineteenth and twentieth centuries reconstructed from a multiyear sea ice index from Southwestern Greenland. Journal of Climate, v. 16, p. 2782-2791.

Smith, L.M., Alexander, C., Jennings, A.E., 2002, Accumulation in East Greenland Fjords and on the continental shelves adjacent to the Denmark Strait over the last century based on 210Pb geochronology. Arctic, v. 55, p. 109-12

 

tl_files/music_academy/campus/Dissemination/marineproxyData_JAndrews.png

Fig 1. Principal component scores on marine climate proxies from NW/N Iceland (Axford et al., 2011) and standard climatic units.

 

Fig 2. Map of the Denmark Strait area and the location of cores

 

Fig 3. Calcite wt% from a combined HU93030-019B and MD99-2322---there is a short gap between the two records---compared with the 1st axis PC scores from the N Iceland proxies (Fig. 1).

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