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

Abstract

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.

Sea Ice Control on Winter Subsurface Temperatures of the North Iceland Shelf During the Little Ice Age: A TEX86 Calibration Case Study

“…Percent quartz ranges from 1.4% to 2.7%, whereas calcite ranges from 5.4% to 8.3% (Figures a and b). Recent analyses using mineral mixtures with known quartz wt % of 3.5 and 1.5 (Andrews et al, ) confirm that these small amounts of quartz can be correctly measured. Prior to ~1250 CE, quartz is relatively low, and calcite is the highest of the record, suggesting a dominance of warmer Atlantic waters at this time.…”

Ocean surface and bottom water conditions, iceberg drift and sediment transport on the North Iceland margin during MIS 3 and MIS 2

“…The Holocene record mimics that from many sites on the North Icelandic Shelf (NIS) in showing an increase in quartz toward the present-day (Andrews et al, 2019).…”

“…1C). Thirty years of observations on the presence of icebergs (Andrews et al, 2019), their Fig. 7A) indicate that icebergs from E/NE Greenland drift across the site.…”

“…There is no general theory about the association of sea ice and icebergs and there is no observational census of the icebergs being transported in the EGC as there is for the Labrador Shelf off Newfoundland, apart from a 30-yr count of icebergs on the Iceland shelves (Jónsdóttir in Andrews et al, 2019). However, Cabedo-Sanz et al ( 2016) and Darby et al (2017) showed that Holocene variations in the wt% of quartz and the sea ice biomarker IP25 co-varied in cores to the west and south of #2274, yet this was not the case at #2274 during MIS 2 and MIS 3 (Figs.…”

Cold season warming in the North Atlantic during the last 2000 years: Evidence from Southwest Iceland

“…Water isotope records from ice cores from Svalbard and a stalagmite from the Central Alps are sensitive to winter air temperatures during the instrumental period, but changes in the moisture source and seasonality of precipitation over time can alter long-term temperature interpretations (Isaksson et al, 2005;Mangini et al, 2005;Divine et al, 2011a, b). In Iceland, records of increasing drift ice along the North Icelandic shelf are sensitive to cold season temperature but are also strongly influenced by different ocean currents and are in direct contrast to records from Western Iceland (Ogilvie et al, 1984;Hopkins, 1991;Moros et al, 2006;Andrews et al, 2019). Although our record lacks a local calibration, we argue that the U 37 K record from VGHV provides a robust, albeit qualitative, record of cold season temperature given the unique seasonal growth ecology of Group I haptophytes in NH lakes.…”