A community-based geological reconstruction of Antarctic Ice Sheet deglaciation since the Last Glacial Maximum

A robust understanding of Antarctic Ice Sheet deglacial history since the Last Glacial Maximum is important in order to constrain ice sheet and glacial-isostatic adjustment models, and to explore the forcing mechanisms responsible for ice sheet retreat. Such understanding can be derived from a broad range of geological and glaciological datasets and recent decades have seen an upsurge in such data gathering around the continent and Sub-Antarctic islands. Here, we report a new synthesis of those datasets, based on an accompanying series of reviews of the geological data, organised by sector. We present a series of timeslice maps for 20ka, 15ka, 10ka and 5ka, including grounding line position and ice sheet thickness changes, along with a clear assessment of levels of confidence. The reconstruction shows that the Antarctic Ice sheet did not everywhere reach the continental shelf edge at its maximum, that initial retreat was asynchronous, and that the spatial pattern of deglaciation was highly variable, particularly on the inner shelf. The deglacial reconstruction is consistent with a moderate overall excess ice volume and with a relatively small Antarctic contribution to meltwater pulse 1a. We discuss key areas of uncertainty both around the continent and by time interval, and we highlight potential priorit. © 2014 The Authors

Correlation of the dust index with insolation maxima and monsoon index.

<p>The dust index of the influx pulses D1, D3, D4, D5 and D6 in core M40/4_SL71 is correlated with (A), the insolation maximum [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0170989#pone.0170989.ref062" target="_blank">62</a>] and (B), the monsoon index of the preceding pluvial phase [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0170989#pone.0170989.ref001" target="_blank">1</a>]. The calculated dust index for phase D1 is a minimum value, because this phase is still active.</p

Data used for constructing the age model for the investigated sediment core M40/4_SL71.

<p>Data used for constructing the age model for the investigated sediment core M40/4_SL71.</p

Correlation of M40/4_SL71 dust record with other proxy climate data.

<p>(A) June insolation at 30°N [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0170989#pone.0170989.ref062" target="_blank">62</a>]. (B) Speleothem δ¹⁸O record of Soreq Cave, Israel [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0170989#pone.0170989.ref063" target="_blank">63</a>]. (C) Saharan dust record from core M51/3_SL143 in the Aegean Sea documented by the kaolinite/chlorite ratio [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0170989#pone.0170989.ref016" target="_blank">16</a>]. (D) Saharan dust record from core M40/4_SL71 in the Ionian Sea documented by the kaolinite/chlorite ratio, with dust pulses D1 to D6 (for high resolution see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0170989#pone.0170989.g002" target="_blank">Fig 2</a>). Grey bars indicate sapropel layers (S). Younger Dryas (YD), Heinrich Events (H) and other cold events (o–t) are labelled [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0170989#pone.0170989.ref019" target="_blank">19</a>]. MIS = Marine Isotope Stage.</p

Location and North African vegetation and drainage changes between humid and arid phases.

<p>(A) Simulated biome distribution (simplified after [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0170989#pone.0170989.ref004" target="_blank">4</a>]) and North African drainage pattern (simplified after [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0170989#pone.0170989.ref011" target="_blank">11</a>]; no data for the southwest part of the map) during the early Holocene humid phase. (B) Biome distribution at present-day (simplified after [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0170989#pone.0170989.ref004" target="_blank">4</a>]). 1: hot desert; 2: warm grass/shrub; 3: temperate woods/shrub; 4: tropical bush/savannah; 5: tropical dry forest/savannah; 6: tropical forest. Stippled areas: alluvial fans. Red dot: position of the investigated sediment core M40/4_SL71 in the EMS; asterisks: positions of marine sediment core M51/3_SL143 and speleothem Soreq Cave mentioned in the text.</p

Saharan dust record of core M40/4_SL71 from the Ionian Sea.

<p>The dust record is expressed as kaolinite/chlorite ratio, and the dust index (framed numbers) of the dust pulses D1 to D6 is calculated from the kaolinite/chlorite peak areas. Sapropels S1, S3, S4, S5 and S6 are indicated by grey bars, and oxidised sapropels by light grey bars. Tephra layers are shown as green lines. Younger Dryas (YD), Heinrich Events (H) and other cold events of the North Atlantic and Arctic regions (o–t) are labelled [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0170989#pone.0170989.ref019" target="_blank">19</a>]. MIS = Marine Isotope Stage.</p

Additional data for sediment core M40/4_SL71.

<p>(A) Oxygen isotope record (data from [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0170989#pone.0170989.ref050" target="_blank">50</a>]). (B) Concentration of palygorskite within the clay mineral assemblage, including 5-point running average. (C) Concentration of kaolinite within the clay mineral assemblage. Grey bars indicate sapropel layers. (D) Ratios of kaolinite/standard (red) and chlorite/standard (green).</p

Conceptual model of dust dynamics.

<p>(A) Changes in the quantity of fine-grained dust influx to the EMS with time. 1: Background level; 2: Pluvial phase with sapropel formation; 3: Dust phase, 4: Glacial drought. The dotted area was used to calculate the dust index. (B) Sketches for the individual phases labelled in panel (A). 1: Arid periods with restricted deflation of kaolinite from kaolinite-bearing sedimentary rocks. 2: Cessation of aeolian transport of kaolinite during humid periods due to vegetation and reduced wind activity. Clay-rich erosion products accumulate in lake basins. 3: With the return of arid conditions, the kaolinite-rich lake sediments are blown out from the desiccated basins leading to maximum kaolinite influx to the Eastern Mediterranean Sea. 4: Intensified aeolian activity during glacial droughts (Heinrich Events) causes minor kaolinite maxima.</p

Composition and grain sizes of the end members in core M40/4_SL71.

<p>A: grain size end members, B: clay mineral end members, C: XRF end members.</p

Variation patterns of the clay mineral end-member loadings in core M40/4_SL71 through time.

<p>Grey shaded areas mark the sapropels, and the ash layers are indicated by the red lines.</p