Recent Antarctic Peninsula warming relative to Holocene climate and ice-shelf history

Abstract

The Antarctic Peninsula is a region that has experienced very rapid warming over the last 50 years, and this has been attributed with the collapse of a number of ice shelves and accelerating glacier mass loss [1][2][3][4][5][6][7] . In contrast, warming has been comparatively modest over West Antarctica and significant changes have not been observed over most of East Antarctica 8-9 , suggesting that the ice core palaeoclimate records available from these areas may not be representative of the climate history of the Antarctic Peninsula. Here we present an ice core record from James Ross Island that provides the first complete Holocene temperature history for the Antarctic Peninsula. The Antarctic Peninsula experienced an early Holocene temperature optimum followed by a long interval from ~9,200 -2,500 years before present (yrBP; 1950AD) of stable temperatures similar to modern day levels. We find that the late Holocene development of ice shelves on the northeastern Antarctic Peninsula was coincident with pronounced cooling from 2,500 to 550 yrBP, which was part of a millennial-scale climate excursion with opposing anomalies on the east and west Antarctic Peninsula. Whilst warming of the northeastern Antarctic Peninsula began around 600 years ago, the rapid rate of warming over the last century is unusual in the context of natural climate variability over the last two millennia. The connection shown here between past temperature and ice shelf stability suggests that warming for several centuries had left ice shelves on the northeastern Antarctic Peninsula poised for collapse, and that continued warming to temperatures that now exceed the stable conditions that persisted here for most of the Holocene is likely to see ice shelf instability encroach further southward along the Antarctic Peninsula.The Antarctic Peninsula is currently one of the most rapidly warming regions on Earth (Fig. 1a) 1 .Historical observations since 1958 at Esperanza Station (Fig. 1b) 2), which plays a role in driving present day variability of the Antarctic Dipole 21 . Antarctic Dipole-like cooling of the Weddell Sea in the late Holocene, and the propagation of these ocean temperature and sea ice anomalies along the eastern Antarctic Peninsula by the Weddell Gyre, may have also aided the rapid establishment of ice shelves in this region during the late Holocene.Sustained warming at James Ross Island began approximately 600 years ago (Fig. 4a). Lake sediments from Beak Island in Prince Gustav Channel also indicate warming beginning at ~1410 AD 18 ,and together these records demonstrate the absence of a widespread Little Ice Age signal on the Antarctic Peninsula that was comparable to northern hemisphere climate 22 (Fig. 4a). The overall rate of pre-anthropogenic temperature rise at JRI from 1400 AD to 1850 AD equates to 0.22 ± 0.06 °C per century. However, there are times in this interval when warming occurred at a much faster rate.Using annual-resolution data, trends were calculated for the JRI temperature record since 2,000 yrBP over moving ...

When did the Anthropocene begin? A mid-twentieth century boundary level is stratigraphically optimal

“…This might well be effective regionally, but we consider that it would not be as widely traceable as a boundary placed at the youngest of the three main candidate levels, that we discuss below. Besides, the Little Ice Age itself is not identifiable globally e it is most prominent in the Northern Hemisphere, and absent from the Antarctic Peninsula (Mulvaney et al, 2012).…”

Acceleration of snow melt in an Antarctic Peninsula ice core during the twentieth century

“…The deuterium-isotope (δD) composition of the JRI ice core is used as a proxy for mean annual temperature at the ice-core site 18,19 . Previous assessments against meteorological reanalysis data since 1979 show that the isotope signal contains summer and winter temperature information and is not biased on seasonal or interannual timescales by snow accumulation 18 .…”

“…This first ice-core reconstruction of melt history for the Antarctic Peninsula is particularly valuable as it is derived from the region (Fig. 1a) where recent rapid atmospheric warming 19,20 is believed to have increased ice melt, leading to widespread ice-shelf thinning and collapse [3][4][5][21][22][23] and accelerated glacier mass loss 24,25 .…”

“…In this study, we measure the annual melt intensity preserved in the James Ross Island (JRI) ice core 18,19 and examine this alongside the ice-core isotope record of mean temperature change over the past 1,000 years. This first ice-core reconstruction of melt history for the Antarctic Peninsula is particularly valuable as it is derived from the region (Fig.…”

Borehole temperatures reveal a changed energy budget at Mill Island, East Antarctica, over recent decades

“…3). Further, these results can be set in the context of wider Antarctic warming, with comparable Antarctic Peninsula warming (Mulvancy et al, 2012), a reconstructed recent temperature trend of up to 0.8 K decade −1 for the West Antarctic Ice Sheet divide (Orsi et al, 2012) and large but spatially variable temperature trends in inland Dronning Maud Land, East Antarctica (Muto et al, 2011).…”