Tracking Holocene drift-ice limits on the northwest–southwest Iceland shelf: Comparing proxy data with observation and historical evidence

Publisher's version (útgefin grein)We detail variations in the weight percent (wt%) of quartz, a proxy for drift ice, in fifteen marine sediment cores from the northwest, west, and southwest Iceland shelf throughout the past 10 cal ka BP. We present the first map of iceberg distributions in Iceland waters between 1983 and 2011 and a new compilation of sea-ice records in the century from 850 to 1950 CE. The wt% of quartz, determined by quantitative X-ray diffraction (qXRD) analysis, is used to evaluate changes in the importation of drift ice. Small wt% of quartz were added to milled basalt (0% quartz), and to a mixture of non-clay and clay minerals; the qXRD method replicated 0 percent quartz, while measured 1–3 percent quartz always resulted in a “presence” estimate. The outer sites in the northwest sector lie close to the average position of the sea-ice margin between 1870 and 1920 CE; the southwest shelf sites lie south of this limit. Transects of cores along the Húnaflói and Djúpáll troughs indicate that the traces of drift ice decrease rapidly landward from the outer sites. The cores from the west/southwest of Iceland have limited amounts of quartz, generally possibly limited incursions of drift ice.JTA acknowledges the support of the National Science Foundation for much of the qXRD data reported here. Wendy Roth is acknowledged for her assistance in the XRD Laboratory and several undergraduate research assistants have throughout the years been extremely helpful in running samples from the cores used in this study. Cruise B997 was supported by the Iceland Marine Institute and NSF grant ATM-9531397 and the MD99 Marion Dufresne cruise was in part supported by NSF-OCE and by The Icelandic Research Center (RANNIS). RANNIS supported the Icelandic research on MD99-2264 and MD99-2269. We thank the editor Dr. Anne E. Jennings, Dr. John Jaeger, and two other reviewers for the time and effort in making substantive recommendations for the improvement of the article.Peer Reviewe