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Edited by Eugene Domack, Hamilton College, Clinton, NY, and accepted by the Editorial Board September 21, 2011 (received for review April 20, 2011)
Article Figures & SI
Figures
- Fig. 1.
The ice shelves of northern Ellesmere Island in 2008 (A and B) and changes in the margin of the WHIS during the 20th century. The data from 1962 (C) and 1906 (D) are from refs. 51 and 52, respectively. The hatched white areas represent ice rises, the plus sign in Disraeli Fiord is the coring location, and the thin lines on the WHIS in B indicate fractures present after summer 2008. S, Serson Ice Shelf; P, Petersen Ice Shelf; Mi, Milne Ice Shelf; A, Ayles Ice Shelf; Ma, Markham Ice Shelf; AIC, the northern margin of the Agassiz Ice Cap; ML, Murray Lake.
- Fig. 2.
Age–depth model and correlation of Disraeli Fiord to regional paleomagnetic records. (A) Geomagnetic field model output (46) and smoothed curve (○). (B) Relative paleointensity (RPI) from Murray Lake, Ellesmere Island (45) and smoothed curve (⋄). (C) RPI of overlapping Disraeli Fiord core sections (□). Symbols along the y axis represent 14C dates (⋄) and paleomagnetic tie points (i.e., inflection points in paleomagnetic data where our records were tied to published curves; ○) used in age–depth model construction. (Inset) Bayesian age–depth model.
- Fig. 3.
Holocene profiles of sediment indicators in Disraeli Fiord. (A) Mn:Fe (XRF ratios: curves, upper x axis) and Mn concentration (ICP-AES: □, lower x axis). (B) Ti (XRF counts⋅s−1 divided by total kilocounts⋅s−1: curves, upper x axis) and ICP-AES concentrations (□, lower x axis). XRF data: blue lines represent the upper core section taken at 55-m depth, and purple lines indicate the lower section from 69-m depth. The thin lines represent the raw data measured at 200-μm intervals and the thicker, darker lines are locally weighted scatterplot smoothing (LOESS)-smoothed curves. (C) Percentage TOC. (D) δ13CORG (vs. Vienna Pee Dee Belemnite). (E) Percentage TIC. (F) Total pigment concentration, where the shaded area represents a 30× exaggeration to show trends in low concentration samples. (G) The 2σ-calibrated 14C age ranges for driftwood samples from Disraeli Fiord (ref. 16 and refs. therein). (H) Ellesmere Island/Greenland composite Holocene ice-core temperature record (53). Symbols along the left y axis represent 14C dates (⋄) and paleomagnetic tie points (○) used in age–depth model construction (Materials and Methods). Comp. depth, composite core depth (in cm) below sea floor.
- Fig. 4.
Indicators of epishelf conditions from 5.7 cal ka BP to present. (A) Magnetic susceptibility from two overlapping core sections. (B) Chl-b:a calculated as the ratio of the sum of chl-b and degradation products to total chl-a and degradation products. (C) IP25 sea-ice biomarker record from the central Canadian Arctic Archipelago (33). (D) Forams: sediment foraminiferal abundances. (E) Sr:Ca ratios (Itrax). Light blue line, raw data; blue line, locally weighted scatterplot smoothing (LOESS)-smoothed data. (F) Greenland Ice Core Project (GRIP) ice-core winter δ18O temperature proxy (32). Magnetic susceptibility records are from both core sections, Sr:Ca ratio is taken from the upper core section alone, and other records are composites from the overlapping core sections (SI Materials and Methods). The shading represents deviations from the median for the last 5.0 cal ka BP, except for chl-b:a (B), whose value (0.4) represents the transition between ratios indicative of Arctic freshwater and marine phytoplankton communities. Symbols along the left y axis represent 14C dates (⋄) and paleomagnetic tie points (○) used in age–depth model construction.
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Holocene dynamics of the Arctic's largest ice shelf
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