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Abstract: The Antarctic Peninsula is one of the fastest-warming regions on Earth, but its palaeoenvironmental history south of 63° latitude is relatively poorly documented, relying principally on the marine geological record and short ice cores. In this paper, we present evidence of late-Quaternary environmental change from the Marguerite Bay region combining data from lake sediment records on Horseshoe Island and Pourquoi-Pas Island, and raised beaches at Horseshoe Island, Pourquoi-Pas Island and Calmette Bay. Lake sediments were radiocarbon dated and analysed using a combination of sedimentological, geochemical and microfossil methods. Raised beaches were surveyed and analysed for changes in clast composition, size and roundness. Results suggest a non-erosive glacial regime could have existed on Horseshoe Island from 35,780 (38,650–33,380) or 32,910 (34,630–31,370) cal yr BP onwards. There is radiocarbon and macrofossil evidence for possible local deglaciation events at 28,830 (29,370–28,320) cal yr BP, immediately post-dating Antarctic Isotopic Maximum 4, and 21,110 (21,510–20,730 interpolated) cal yr BP coinciding with, or immediately post-dating, Antarctic Isotopic Maximum 2. The Holocene deglaciation of Horseshoe Island commenced from 10,610 (11,000–10,300) cal yr BP at the same time as the early Holocene temperature maximum recorded in Antarctic ice cores. This was followed by the onset of marine sedimentation in The Narrows, Pourquoi-Pas Island, before 8850 (8480–9260) cal yr BP. Relative sea level high stands of 40.79 m above present at Pourquoi-Pas Island and 40.55 m above present at Calmette Bay occurred sometime after 9000 cal yr BP and suggest that a thicker ice sheet, including grounded ice streams, was present in this region of the Antarctic Peninsula than that recorded at sites further north. Isolation of the Narrows Lake basin on Pourquoi-Pas Island shows relative sea level in this region had fallen rapidly to 19.41 m by 7270 (7385–7155) cal yr BP. Chaetoceros resting spores suggest high productivity and stratified surface waters in The Narrows after 8850 (9260–8480) cal yr BP and beach clasts provide evidence of a period of increased wave energy at approximately 8000 yr BP. Lake sediment and beach data suggest an extended period of regional warming sometime between 6200 and 2030 cal yr BP followed by the onset of Neoglacial conditions from 2630 and 2030 cal yr BP in Narrows Lake and Col Lake 1, respectively. Diatom and δ13C vs C/N and macrofossil evidence suggest a potential increase in the number of birds and seals visiting the Narrows Lake catchment sometime after 2100 (2250–2000) cal yr BP, with enhanced nutrient enrichment evident after 1150 (1230–1080) cal yr BP, and particularly from c. 460 (540–380) cal yr BP. A very recent increase in Gomphonema species and organic carbon in the top centimetre of the Narrows Lake sediment core after c. 410 (490–320) cal yr BP, and increased sedimentation rates in the Col Lake 1 sediment core, after c. 400 (490–310) cal yr BP may be a response to the regional late-Holocene warming of the Antarctic Peninsula. [Copyright &y& Elsevier]

Raised beach ridges on Livingston Island of the South Shetland Islands display variations in both quantity and source of ice rafted detritus (IRD) received over time. Whereas the modem beach exhibits little IRD, all of which is of local origin, the next highest beach (∼250 14C yr BP) has large amounts, some of which comes from as far away as the Antarctic Peninsula. Significant quantities of IRD also were deposited ∼1750 14C yr BP. Both time periods coincide with generally cooler regional conditions and, at least in the case of the ∼250 yr old beach, local glacial advance. We suggest that the increases in ice rafting may reflect periods of greater glacial activity, altered ocean circulation, and/or greater iceberg preservation during the late Holocene. Limited IRD and lack of far-travelled erratics on the modem beach are both consistent with the ongoing warming trend in the Antarctic Peninsula region. [ABSTRACT FROM AUTHOR]

At a global scale, there is no evidence for synchronous multi-decadal warm (‘Medieval Warm Period’, MWP) or cold (‘Little Ice Age’, LIA) periods in the late Holocene. On the other hand, there is good correspondence globally in the timing of MWP or LIA and phases of glacier retreat and advance, respectively, with local exceptions mainly explained by the precipitation regime. Antarctica exhibits contrasting patterns, both regarding the existence of these two historical climatic periods and the glacial responses to climatic forcing. Here, we present evidence for glacial retreat corresponding to the MWP and a subsequent LIA advance at Rothera Point (67°34′S; 68°07′W) in Marguerite Bay, western Antarctic Peninsula. Deglaciation started at ca. 961–800 cal. yr BP or before, reaching a position similar to or even more withdrawn than the current state, with the subsequent period of glacial advance commencing between 671 and 558 cal. yr BP and continuing at least until 490–317 cal. yr BP. Based on new radiocarbon dates, during the MWP, the rate of glacier retreat was 1.6 m yr−1, which is comparable with recently observed rates (~0.6 m yr−1 between 1993 and 2011 and 1.4 m yr−1 between 2005 and 2011). Moreover, despite the recent air warming rate being higher, the glacial retreat rate during the MWP was similar to the present, suggesting that increased snow accumulation in recent decades may have counterbalanced the higher warming rate. [ABSTRACT FROM AUTHOR]

Analyses of a 12 m marine sediment core from Neny Fjord, Marguerite Bay, Antarctic Peninsula (68.2571°S, 66.9617°W), yield a high-resolution record of Holocene climate variability. The sediments preserve signals of past glacial and marine environments and offer a unique insight into atmospheric and oceanic forcings on the western Antarctic Peninsula climate. Dating of basal material reveals that deglaciation of the fjord occurred prior to 9040 cal. yr BP and provides a minimum constraint on the timing of deglaciation close to the southern Antarctic Peninsula ice-divide. Continuous deposition of ice-distal sediments and seasonally open-water diatoms indicates that the site has not been over-ridden by glacier ice during the Holocene. A facies of sand-rich material offers the only evidence of a localized glacier advance, during the mid Holocene. Statistical analysis of diatom assemblage data reveals several climatic episodes of varying magnitude and duration. These include an early-Holocene warm period (∼9000 and ∼7000 cal. yr BP), potentially associated with influx of Circumpolar Deep Water onto the continental shelf and coinciding with widespread glacial retreat and Holocene collapse of the George VI Ice Shelf. The mid-Holocene (∼7000 to ∼2800 cal. yr BP) sediments are characterized by diatom assemblages indicative of less pervasive sea-ice cover and prolonged growing seasons with evidence of increased meltwater discharge from ∼4000 cal. yr BP. The youngest sediments (∼2800 cal. yr BP to present) contain a record that is consistent with the widely documented 'neoglacial' period followed by an abrupt reversal and climate amelioration from sometime after ∼200 cal. yr BP. [ABSTRACT FROM AUTHOR]

The Antarctic Peninsula is one of the three fastest warming regions on Earth. Here we review Holocene proxy records of marine and terrestrial palaeoclimate in the region, and discuss possible forcing mechanisms underlying past change, with a specific focus on past warm periods. Our aim is to critically evaluate the mechanisms by which palaeoclimate changes might have occurred, in order to provide a longer-term context for assessing the drivers of recent warming. Two warm events are well recorded in the Holocene palaeoclimate record, namely the early Holocene warm period, and the 'Mid Holocene Hypsithermal' (MHH), whereas there are fewer proxy data for the 'Mediaeval Warm Period' (MWP) and the 'Recent Rapid Regional' (RRR) warming. We show that the early Holocene warm period and MHH might be explained by relatively abrupt shifts in position of the Southern Westerlies, superimposed on slower solar insolation changes. A key finding of our synthesis is that the marine and terrestrial records in the AP appear to show markedly different behaviour during the MHH. This might be partly explained by contrasts in the seasonal insolation forcing between these records. Circumpolar Deep Water (CDW) has been implicated in several of the prominent changes through the Holocene but there are still differences in interpretation of the proxy record that make its influence difficult to assess. Further work is required to investigate contrasts between marine and terrestrial proxy records, east-west contrasts in palaeoclimate, the history of CDW, to retrieve a long onshore high resolution record of the Holocene, and determine the role of sea ice in driving or modulating palaeoclimate change, along with further efforts to study the proxy record of the RRR and the MWP. [ABSTRACT FROM AUTHOR]

Palmer Deep sediment cores are used to produce the first high-resolution, continuous late Pleistocene to Holocene time-series from the Antarctic marine system. The sedimentary record is dated using accelerator mass spectrometer radiocarbon methods on acid insoluble organic matter and foraminiferal calcite. Fifty-four radiocarbon analyses are utilized in the dating which provides a calibrated timescale back to 13 ka BP. Reliability of resultant ages on organic matter is assured because duplicates produce a standard deviation from the surface age of less than laboratory error (i.e., ±50 years). In addition, surface organic matter ages at the site are in excellent agreement with living calcite ages at the accepted reservoir age of |1260 years for the Antarctic Peninsula. Spectral analyses of the magnetic susceptibility record against the age model reveal unusually strong periodicity in the 400, |200 and 50–70 year frequency bands, similar to other high-resolution records from the Holocene but, so far, unique for the circum-Antarctic. Here we show that comparison to ice-core records of specific climatic events (e.g., the ‘Little Ice Age’, Neoglacial, Hypsithermal, and the Bølling/Allerød to Younger Dryas transition) provides improved focus upon the relative timing of atmosphere/ocean changes between the northern and southern high latitudes. [ABSTRACT FROM AUTHOR]