Introduction | Oceanography and climate | Modern Glaciology | Geological history | References | Comments |
Introduction
This section largely taken from Davies et al., 2012 (Quaternary Science Reviews)[1].
The Antarctic Peninsula Ice Sheet (sometimes written as APIS) is widely regarded as sensitive to climate change due to its small size and northerly location, and because this region is one of the most rapidly warming places in the world[2-5].
This sensitivity has been manifest through the collapse of numerous ice shelves, increased ice velocities, and the retreat and thinning of glaciers and ice caps[6-10].
The Antarctic Peninsula is a relatively long, thin spine Alpine-style mountain chain[1]. These mountains extend north towards the Drake Passage, reaching 63°S. The Antarctic Peninsula is 70 km wide, with an average height of ~1500 m[11]. It is 522,000 km2 in area and 80% ice-covered[12].
You can explore the Antarctic Peninsula Ice Sheet through the Google Map below. Note the flat ice shelves, the islands on the western and eastern Peninsula, and the flowline structures of the glaciers as they flow into the sea. You can also see the rifts in the Larsen Ice Shelf and the few mountain summits that poke through the ice.
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Oceanography and climate
These mountains form a significant barrier to the persistent westerly, moisture-laden winds. The climatic regime either side of the Antarctic Peninsula is therefore quite different.
In the Bellingshausen Sea, there is a polar maritime climate, and in the Weddell Sea, a cold, dry, polar continental climate[1, 3, 11, 13, 14].
The Weddell Sea is further cooled by the Weddell Sea Gyre, which circulates sea ice, icebergs and cold water clockwise towards the northern Antarctic Peninsula[15]. Sea ice also modulates sea surface temperatures in the Weddell Sea[3, 16].
Modern Glaciology
The modern Antarctic Peninsula Ice Sheet is approximately 500 m thick, with outlet glaciers flowing out east and west[17]. Summer air temperatures are greater than 0°C at sea level, and the mass balance of Antarctic Peninsula glaciers is largely controlled by surface melting and glacier calving.
Many of these tidewater glaciers are grounded, particularly on the north-western Peninsula[18]. However , there are large ice shelves fringing the Antarctic Peninsula south of 68°S in the east and 70°S in the west[1, 8].
The Antarctic Peninsula Ice Sheet contains enough water to raise sea level by 0.24m on full melting[9], and currently contributes 0.22 ± 0.16 mm per year to sea level rise[19].
The Antarctic Peninsula is particularly important because several large ice free areas, for example, on James Ross Island, Alexander Island and South Shetland Islands preserve important palaeoenvironmental archives [e.g., 20, 21-29].
In addition to these, the Bransfield Strait (and its topographic expression, Bransfield Basin) is an 1800 m deep marginal basin separating the South Shetland Islands from the Antarctic Peninsula. It is infilled with thick sequences of marine and glaciomarine sediments, which provide detailed information on Antarctic Peninsula Ice Sheet fluctuations throughout the Quaternary [30-35].
The Palmer Deep, south of Anvers Island, is 1000 m deep and 200 km2 in area, and also contains a long record of glacial activity and Holocene environmental variability [36, 37].
Geological history
The Antarctic Peninsula was once part of the now fragmented Gondwana continent, that extended from South America through the Antarctic Peninsula and New Zealand until the Late Cretaceous[38].
Arc magnetism (resulting in volcanoes around the Antarctic Peninsula) was active throughout the Cenozoic, formed in response to subduction of the proto-Pacific ocean floor along the western margin of the Antarctic Peninsula. The Antarctic Peninsula basement rocks are the Trinity Peninsula Group; these intermediate grade rocks were metamorphosed during this subduction.
The Antarctic Peninsula is bordered to the east (for example, James Ross Island) by a back-arc basin stratigraphy of thick Jurassic and Cretaceous marine shales and siltstone[39]. Deposits began to accumulate in James Ross Basin, providing evidence of the earliest glaciation.
The Drake Passage between South America and the Antarctic Peninsula began to open following fragmentation and brittle response of the crust from compressive to extensional forces[39]. During this time (Palaeogene and Neogene; cf. Table 1), the Mesozoic rocks that now form the Antarctic Peninsula mountains were uplifted.
This uplift aided the accumulation of ice masses across the Peninsula and resulted in glacial and glacially-related erosion and deposition on the continental shelf. During this period, the Antarctic landmass also moved southwards, towards its present position. See Past Behaviour for information on the earliest glacierisation of the Antarctic Peninsula.
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Further reading
- Antarctic Peninsula photographs
- Evolution of the Antarctic Peninsula Ice Sheet
- West Antarctic Ice Sheet
- East Antarctic Ice Sheet
- Antarctic Peninsula glacier recession
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A few pages of my book deal with the Scotia Basin, the Palmer Peninsula and the curve of Souh America. If you would like a copy I would appreciate your comment’s.since I am currently checking the draft of the updated edition.