Antarctic Peninsula
Beneath the ice sheet that covers it, the Antarctic Peninsula consists of a string of bedrock islands; these are separated by deep channels whose bottoms lie at depths considerably below current sea level.
[2] The marine ecosystem around the western continental shelf of the Antarctic Peninsula (WAP) has been subjected to rapid climate change.
This regional warming has caused multi-level responses in the marine ecosystem such as increased heat transport, decreased sea ice extent and duration, local declines in ice-dependent Adélie penguins, increase in ice-tolerant gentoo and chinstrap penguins, accelerated greening due to the spread of moss, alterations in phytoplankton and zooplankton community composition as well as changes in krill recruitment, abundance and availability to predators.
[3][4][5][6] The Antarctic Peninsula is currently dotted with numerous research stations, and nations have made multiple claims of sovereignty.
Three days later, on 30 January 1820, Edward Bransfield and William Smith, with a British expedition, were the first to chart part of the Antarctic Peninsula.
The next confirmed sighting was in 1832 by John Biscoe, a British explorer, who named the northern part of the Antarctic Peninsula as Graham Land.
[1] Other portions of the peninsula are named by and after the various expeditions that discovered them, including the Bowman, Black, Danco, Davis, English, Fallières, Nordenskjöld, Loubet, and Wilkins Coasts.
The Antarctic Peninsula and Cape Horn create a funneling effect, which channels the winds into the relatively narrow Drake Passage.
[21][22] Because of issues concerning global climate change, the Antarctic Peninsula and adjacent parts of the Weddell Sea and its Pacific continental shelf have been the subject of intensive geologic, paleontologic, and paleoclimatic research by interdisciplinary and multinational groups over the last several decades.
This research shows the dramatic changes in climate, which have occurred within this region after it reached its approximate position within the Antarctic Circle during the Cretaceous Period.
Plant fossils found within the Late Cretaceous (Coniacian and Santonian-early Campanian) strata of the Hidden Lake and Santa Maria formations, which outcrop within James Ross, Seymour, and adjacent islands, indicate that this emergent volcanic island arc enjoyed warm temperate or subtropical climates with adequate moisture for growth and without extended periods of below freezing winter temperatures.
[25][29] After the peak warmth of the Cretaceous thermal maximum the climate, both regionally and globally, appears to have cooled as seen in the Antarctic fossil wood record.
Later, warm high-latitude climates returned to the Antarctic Peninsula region during the Paleocene and early Eocene as reflected in fossil plants.
At this time, the Antarctic Peninsula formed as the bedrock islands underlying it were overridden and joined by an ice sheet in the early Pliocene about 5.3–3.6 Ma.
[23][24][25] During the Last Glacial Maximum, about 20,000 to 18,000 years ago, the ice sheet covering the Antarctic Peninsula was significantly thicker than it is now.
[32] Research by the United States Geological Survey has revealed that every ice front on the southern half of the peninsula experienced a retreat between 1947 and 2009.
[38] The Intergovernmental Panel on Climate Change has been unable to determine the greatest potential effect on sea level rise that glaciers in the region may cause.
[37] The coasts of the peninsula have the mildest climate in Antarctica and moss and lichen-covered rocks are free of snow during the summer months, although the weather is still intensely cold and the growing season very short.
[19][20][39] Seabirds of the Southern Ocean and West Antarctica found on the peninsula include: southern fulmar (Fulmarus glacialoides), the scavenging southern giant petrel (Macronectes giganteus), Cape petrel (Daption capense), snow petrel (Pagodroma nivea), the small Wilson's storm-petrel (Oceanites oceanicus), imperial shag (Phalacrocorax atriceps), snowy sheathbill (Chionis alba), the large south polar skua (Catharacta maccormicki), brown skua (Catharacta lönnbergi), kelp gull (Larus dominicanus), and Antarctic tern (Sterna vittata).
[40] Although this very remote part of the world has never been inhabited and is protected by the Antarctic Treaty System, which bans industrial development, waste disposal and nuclear testing, there is still a threat to these fragile ecosystems from increasing tourism, primarily on cruises across the Southern Ocean from the port of Ushuaia, Argentina.
The analysis of fossil leaves and flowers indicates that semitropical woodlands, which were composed of ancestors of plants that live in the tropics today, thrived within this region during a global thermal maximum with summer temperatures that averaged 20 °C (68 °F).
The paleosols, in which trees are rooted, have physical characteristics indicative of modern soils that form under seasonally dry climates with periodic high rainfall.
[29] These fossil plants are indicative of tropical and subtropical forest at high paleolatitudes during the Middle and Late Cretaceous, which grew in climates without extended periods of below freezing winter temperatures and with adequate moisture for growth.
These Seymour Island region fossils date to about 51.5–49.5 Ma and are dominated by leaves, cone scales, and leafy branches of Araucarian conifers, very similar in all respects to living Araucaria araucana (monkey puzzle) from Chile.
They suggest that the adjacent parts of the prehistoric Antarctic Peninsula were covered by forests that grew in a cool and moist, high-latitude environment during the early Eocene.
[25] During the Cenozoic climatic cooling, the Antarctic Peninsula was the last region of Antarctica to have been fully glaciated according to current research.
Analysis of paleontologic, stratigraphic, and sedimentologic data acquired from the study of drill core and seismic acquired during the Shallow Drilling on the Antarctic Continental Shelf (SHALDRIL) and other projects and from fossil collections from and rock outcrops within Alexander, James Ross, King George, Seymour, and South Shetland Islands has yielded a record of the changes in terrestrial vegetation that occurred within the Antarctic Peninsula over the course of the past 37 million years.
[24][25] This research found that vegetation within the Antarctic Peninsula changed in response to a progressive climatic cooling that started with the initiation of mountain glaciation in the latest Eocene, about 37–34 Ma.
Initially, during the Eocene, this climate cooling resulted in a decrease in diversity of the angiosperm-dominated vegetation that inhabited the northern Antarctic Peninsula.
Eventually, the Antarctic Peninsula was overridden by an ice sheet, which has persisted without any interruption to this day, in the early Pliocene, about 5.3–3.6 Ma.
