High-resolution Holocene climate record from Maxwell Bay, South Shetland Islands, Antarctica

Abstract

The highest resolution Holocene sediment core from the Antarctic Peninsula to date was collected during the fi rst SHALDRIL cruise (NBP0502). Drilling yielded a 108.2-m-long core (87% recovery; site NBP0502-1B) from Maxwell Bay, South Shetland Islands. This high-resolution sediment record comes from a region that is currently experiencing dramatic climate change and associated glacial retreat. Such records can help to constrain the nature of past climate change and causal mechanisms, and to provide a context for evaluating current climate change and its impacts.The base of the drill site sampled till and/or proximal glacimarine sediments resting directly on bedrock. Glacimarine suspension deposits composed of dark greenish gray silty mud with variable diatom abundance and scattered very fi ne sand laminations make up the majority of the sedimentary section. Detailed sedimentological and geochemical analyses, including magnetic susceptibility, total organic carbon (TOC) content, carbon and nitrogen isotopic composition, pebble content, and biogenic silica content, allow subdivision of the glacimarine section into nine units, and seismic facies analyses resulted in the identifi cation of six distinct seismic units. We used 29 radiocarbon ages to construct an age model and calculate sedimentation rates that vary by two orders of magnitude, from 0.7 mm/a to ~30 mm/a. Radiocarbon ages from glacimarine sediments just above the till date back to between 14.1 and 14.8 ka. Thus, ice was grounded in the fjord during the Last Glacial Maximum and eroded older sediments from the fjord. Following initial retreat of grounded ice from Maxwell Bay, the fjord was covered by a permanent fl oating ice canopy, probably an ice tongue. The highest sedimentation rate corresponds to an interval that contains abundant sand laminations and gravelly mud inter vals and likely represents a melt-out phase or period of rapid glacial retreat from 10.1 ka to 8.2 ka. There is no evidence for an early Holocene climatic reversal, as recorded farther south at the Palmer Deep drill site. Minimum sea-ice cover and warm water conditions occurred between 8.2 and 5.9 ka. From 5.9 to 2.6 ka, there was a gradual cooling and more extensive sea-ice cover in the bay. After 2.6 ka, the climate varied slightly, causing only subtle variation in glacier grounding lines. There is no compelling evidence for a Little Ice Age readvance in Maxwell Bay. The current warming and associated glacial response in the northern Antarctic Peninsula appears to be unprecedented in its synchroneity and widespread impact. Modern Climate, Glacial, and Oceanographic ConditionsAtmospheric temperatures for Maxwell Bay average -3 °C, but during the summer months, temperatures commonly rise above freezing For permission to copy, contact editing@geosociety.org

Geomorphology and landforms distribution in selected ice-free areas in the South Shetland Islands, Antarctic Northern Peninsula region

“…On Fildes Peninsula the deglaciation begun between 11 and 9 ka ago (Watcham et al, 2011), and on King George Island (Potter Peninsula) between 11.9 and 5.9 ka while on Byers Peninsula an age of 8.3-5.9 ka has been determined (Toro et al, 2013, Oliva et al, 2016. A regional advance between 6 and 4.5 ka BP (Hall, 2010;Michalchuck et al, 2009) has been detected after a period with less cold conditions between 8.2 and 5.9 ka (Milliken et al 2009). Both periods involve the development of periglacial and permafrost environments on the ice-free areas.…”

Glacial discharge along the west Antarctic Peninsula during the Holocene

“…1a). This peak glacial discharge to the coastal margin was co-incident with ice sheet retreat across the outer 10 and inner 11 Anvers Shelf, the break-up of the Marguerite Bay ice shelf to the south 12 and the transition from perennial to seasonal sea ice in Maxwell Bay to the north 13 (Fig. S1).…”

“…1a) during a time of widespread warmth along the WAP exemplified by ice sheet retreat and thinning 2 , high SSTs 3 and thin sea ice cover with warm winters 4 in Palmer Deep, the collapse of the George VI Ice Shelf (Fig. S1) at 9.6 ka 16 and increased influence of glacial melt and precipitation in Maxwell Bay 13 . This warmth was concomitant with the last influence of orbitally-forced deglaciation 5,15 and ENSO-sensitive proxy records from the Peru margin and Ecuador 5,17 that indicate a persistent warm, mean La Niña-like state (relative to mean El Niño-like conditions).…”

La deglaciación de las áreas libres de hielo de las islas Shetland del Sur (Antártida). Ejemplos de Byers (Livingston) y Barton (King George)

“…Estas áreas corresponderían a nunataks que sobresaldrían notoriamente sobre el relieve circundante. A su vez, la datación de sedimentos marinos en la bahía Maxwell sugiere su deglaciación en torno a 14,1 ka cal BP (Milliken et al, 2009). En el margen nororiental de la PA, las masas glaciares también experimentan un acelerado retroceso a partir de 12.9 ± 1.2 ka (Nývlt et al, 2014).…”

“…Éste es el caso de la Península Fildes (NO de la isla King George), cuyos márgenes fueron deglaciados entre 11 y 9 ka cal BP (Watcham et al, 2011). El retroceso gradual de los glaciares se intensifica en torno a 8 ka cal BP, momento en el que se registran las condiciones más cáli-das del Holoceno en la PA (Bentley et al, 2009;Milliken et al, 2009). Así, en la Península Byers la datación de la base sedimentaria del lago Limnopolar sugiere que este lago apareció en torno a 8,3 ka cal BP.…”