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

John T Andrews,Ingibjörg Jónsdóttir,Áslaug Geirsdóttir

doi:10.1080/15230430.2019.1592648

John T Andrews, Ingibjörg Jónsdóttir + Show 1 more

Open Access

https://doi.org/10.1080/15230430.2019.1592648

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Abstract

ABSTRACTWe 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.

Highlights

The presence of sea ice and icebergs around Iceland (Figure 1; Koch 1945; Wallevik and Sigurjónsson 1998) is an important climatic indicator (Lamb 1979; Ogilvie and Jónsdóttir 2000; Ogilvie and Jónsson 2001)
It is not known whether these limits applied during the mid-to-late Holocene and whether extensive drift ice reached southwest Iceland during the Little Ice Age
At B997-330 close to the coast (Figures 1, 8, and 9), the calcite wt% is a close match to the MD99-2269 data but the quartz wt% are less than 1 percent with rather surprising, if real, “high” peaks of approximately 1 percent in the mid-Holocene between 5.5 and 4 cal ka BP

Summary

Introduction

The presence of sea ice and icebergs (together termed drift ice) around Iceland (Figure 1; Koch 1945; Wallevik and Sigurjónsson 1998) is an important climatic indicator (Lamb 1979; Ogilvie and Jónsdóttir 2000; Ogilvie and Jónsson 2001). Modern satellite and historical observations of the southern and eastern limits of drift ice on the Iceland shelf indicate a limited penetration of drift ice south of Vestfirðir (the northwest peninsula of Iceland; Figure 1). It is not known whether these limits applied during the mid-to-late Holocene (the past ca 5 cal ka) and whether extensive drift ice reached southwest Iceland during the Little Ice Age Fresher, drift ice bearing Arctic and Polar surface waters flow toward Iceland from the Arctic Ocean in the East Greenland and East Iceland Currents (Figure 2). A coastal current (Figure 2A) runs clockwise around Iceland and this can transport glacial meltwater, fluvial runoff, and occasionally sea ice to southwest Iceland

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