Reconstructing Sea Ice Conditions in the Arctic and Sub-Arctic Prior to Human Observations - Arctic Sea Ice Decline: Observations, Projections, Mechanisms, and Implications - page 34

Figure 6. Examples of sea ice cover reconstruction for the last hundreds of years based on cores from the Chukchi Sea
and northern Baffin Bay having exceptionally high sedimentation rates (for core location, see sites A and B in Figure 10
and Table 1). The sedimentation rates in both cores have been evaluated from 210 Pb measurements. The data from core
92-B5 in the Chukchi Sea are from this study, and the data from core 99-76F in the northern Baffin Bay are reported by
Hamel et al . [2002]. The thin lines correspond to the most probable values from sets of five analogues, and the thick lines
correspond to a three-point running mean.

tributed to dilution with fresh water and lowering of salinity
because of ecological characteristics of N. pachyderma that
include minimum salinity requirements (≥34.5 [ Hilbrecht ,
1996]). It is, rather, attributed to brine extrusion occurring

2001; Simstich et al. , 2003; Hillaire-Marcel et al. , 2004].
The offset in δ 18 O values ranges from near −1‰ in the north-
ern Greenland Sea to about −3‰ in the western Arctic Ocean
[e.g., Bauch et al. , 1997; Fisher et al. , 2006]. It cannot be at-

Figure 7. Historical record of sea ice occurrence off the Icelandic coasts (modified from Lamb [1977, Figure 17.13,
p. 452]). Past records of sea ice extent in northwest North Atlantic are available from the accounts of voyages by Irish
monk-explorers and by Vikings who established settlements in Iceland and in southwest Greenland at the end of the
first millennium. Until 1200 A.D., sea ice was reported to occur exceptionally. All historical data suggest minimum sea
ice extent around Iceland and off Greenland during the medieval warm episode and conditions favorable for navigation
across the North Atlantic. Navigation reports and other historical archives show that the spreading of seasonal sea ice
became more and more extensive in the northern North Atlantic after 1250 A.D. During the decade from 1340 to 1350
A.D., the increasing spread of Arctic sea ice around Greenland even forced the old sailing routes along the 65°N parallel
to be abandoned, which caused the decline of the Viking settlements in southern Greenland.