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A palaeoenvironmental study of a peat sequence from Iles Kerguelen (49°S, Indian Ocean) for the Last Deglaciation based on pollen analysis

Henao, Victor LU (2015) In Dissertations in Geology at Lund University GEOR02 20151
Department of Geology
Abstract
In recent years, the Southern Hemisphere (SH) and the vast Southern Ocean (SO) have gained awareness and importance within the scientific community in relation to global climate change and the global CO2 cycle, par-ticularly since the Last Glacial Maximum (LGM) and into the Holocene. It is believed that the Southern Hemi-sphere Westerlies (SHW) play a key role in regulating climate change in the mid-to-high latitudes of the SH, thus reconstructing the SHW latitudinal positioning since the LGM has been crucial. However, terrestrial records of the mid-to-high latitudes are sparse. Most of the evidence is generally constrained to southern South America and New Zealand, and at times reveals contradictory results. Scientists have been trying to... (More)
In recent years, the Southern Hemisphere (SH) and the vast Southern Ocean (SO) have gained awareness and importance within the scientific community in relation to global climate change and the global CO2 cycle, par-ticularly since the Last Glacial Maximum (LGM) and into the Holocene. It is believed that the Southern Hemi-sphere Westerlies (SHW) play a key role in regulating climate change in the mid-to-high latitudes of the SH, thus reconstructing the SHW latitudinal positioning since the LGM has been crucial. However, terrestrial records of the mid-to-high latitudes are sparse. Most of the evidence is generally constrained to southern South America and New Zealand, and at times reveals contradictory results. Scientists have been trying to obtain a clearer picture of shifts in the SHW in the mid-to-high latitudes through analyzing terrestrial records from the island groups that make up the sub-Antarctic region. Here, a c.14000 cal yr BP terrestrial record from Port Douzieme (P12) at Iles Kerguelen (49°S) is analyzed using a multi-proxy approach (lithostratigraphy, magnetic susceptibility, loss on ignition, and pollen). The P12 record reveals clear changes since c.14000 cal yr BP, at which time a sparsely vegetated environ-ment existed, dominated by grasses (Poaceae). Then, the wind tolerant, cushion plant Azorella selago became a much more influential species by c.13600, coinciding with the presence of lacustrine-type-sediments, suggesting windier and wetter conditions. By c.12900 cal yr BP the lowland species Acaena magellanica suddenly expanded, becoming the dominant species and coinciding with the end of the Antarctic Cold Reversal (ACR). Finally, at c.11200 cal yr BP the species Uncinia compacta and Blechnum penna-marina appear in the pollen record, suggest-ing much warmer conditions on the Kerguelen archipelago. The record from P12 was compared with a previous study done by Van der Putten et al. (submitted) at the Estacade site in the Kerguelen archipelago, approximately 50 km northeast of the P12 site. The pollen record from the Estacade site shows a similar vegetation history as the rec-ord from P12 for the Kerguelen archipelago. At the Estacade site, Poaceae is prominent between c.16000-13650 cal yr BP, followed by a period of dominance by the wind tolerant species Azorella selago and Lyallia kerguelensis at 13650 cal yr BP. At around 11200 cal yr BP the lowland species Acaena magellanica and Uncinia compacta ex-panded. Additionally, the pollen record from P12 reveals a higher influence of the SHW at about 13600 cal yr BP, when a great diversity in long distance pollen grains is recorded, coinciding with the expansion of the wind tolerant species Azorella selago, as well as the presence of lacustrine-type-sediments at both the Estacade site and P12. (Less)
Abstract (Swedish)
Under de senaste åren har södra halvklotet och den vidsträckta Södra oceanen fått ökad upp-märksamhet och betydelse inom det vetenskapliga samfundet med avseende på globala klimatförändringar och den globala CO2-cykeln, särskilt vad gäller förhållandena under senaste istidsmaximum (Last Glacial Maximum, LGM) och holocen. Man menar att Västvindbältet på södra halvklotet (Southern Hemisphere Westerlies, SHW) spelar en viktig roll i regleringen av klimatförändringar på mellan- och höga breddgrader på SH. Därmed har det varit av avgörande betydelse att rekonstruera det latitudinella läget av SHW sedan LGM, men kontinentala klimatarkiv från mellan- och höga breddgrader är sällsynta. Merparten av data begränsas till södra Sydamerika och Nya... (More)
Under de senaste åren har södra halvklotet och den vidsträckta Södra oceanen fått ökad upp-märksamhet och betydelse inom det vetenskapliga samfundet med avseende på globala klimatförändringar och den globala CO2-cykeln, särskilt vad gäller förhållandena under senaste istidsmaximum (Last Glacial Maximum, LGM) och holocen. Man menar att Västvindbältet på södra halvklotet (Southern Hemisphere Westerlies, SHW) spelar en viktig roll i regleringen av klimatförändringar på mellan- och höga breddgrader på SH. Därmed har det varit av avgörande betydelse att rekonstruera det latitudinella läget av SHW sedan LGM, men kontinentala klimatarkiv från mellan- och höga breddgrader är sällsynta. Merparten av data begränsas till södra Sydamerika och Nya Zeeland, och dessa ger ibland motsägelsefulla resultat. Forskare har försökt att få en tydligare bild av förändringarna av SHW på mellan- och höga breddgrader genom att analysera kontinentala arkiv från de ögrupper som utgör den Subantarktiska regionen. Här presenteras resultaten från en multi-proxy-undersökning (litostratigrafi, magnetisk susceptibilitet, glödförlust, och pollen) av en ca 14000 år gammal kontinental lagerföljd från Port Douzieme (P12) på Kerguelen-öarna (49 °S). Dessa visar på tydliga förändringar sedan ca 14000 cal yr BP, då området känneteck-nades av ett glest vegetationstäcke dominerat av gräs (Poaceae). Betydelsen av den vindtoleranta, kuddformiga väx-ten Azorella selago ökade för ca 13600 år sedan samtidigt som vattenavsatta sediment börjar uppträda, vilket tyder på blåsigare och blötare förhållanden. Omkring 12900 cal yr BP expanderade plötsligt Acaena magellanica som idag förekommer i öns låglandsområden, och denna art blev därefter dominerande. Förändringen sammanfaller med slutet av Antarctic Cold Reversal (ACR). Slutligen, vid ca 11200 cal yr BP uppträder arterna Uncinia compacta och Blechnum penna-marina för första gången i pollendata, vilket tyder på betydligt varmare förhållanden i Kerguelen-arkipelagen. Resultaten från P12 jämfördes med en tidigare studie utförd av Van der Putten (submitted) på lokalen Estacade i Kerguelen-arkipelagen, ca 50 km nordost om P12. Den vegetationshistoria som pollenanalysen från Estacade visar för Kerguelen-arkipelagen liknar den som ses i data från P12. På Estacade-lokalen är Poaceae fram-trädande mellan ca 16000 och 13650 cal yr BP, följt av en period med dominans av de vindtoleranta arterna Azo-rella selago och Lyallia kerguelensis ca 13650 cal yr BP. Omkring 11200 cal yr BP expanderade låglandsarterna Acaena magellanica och Uncinia compacta. Pollenanalysen av P12 visar därutöver en ökad påverkan av SHW från ca 13600 cal yr BP, då ett stort antal pollentyper transporterade över stora avstånd påträffas, vilket sammanfaller med expansionen av den vindtoleranta arten Azorella selago samt förekomsten av vattenavsatta sediment både vid Estacade och P12. (Less)
Please use this url to cite or link to this publication:
author
Henao, Victor LU
supervisor
organization
course
GEOR02 20151
year
type
H2 - Master's Degree (Two Years)
subject
publication/series
Dissertations in Geology at Lund University
report number
430
language
English
additional info
External supervisor: Cyriel Verbruggen, Gent University, Belgium
id
5364988
date added to LUP
2015-05-04 14:42:09
date last changed
2015-05-04 14:42:09
@misc{5364988,
  abstract     = {In recent years, the Southern Hemisphere (SH) and the vast Southern Ocean (SO) have gained awareness and importance within the scientific community in relation to global climate change and the global CO2 cycle, par-ticularly since the Last Glacial Maximum (LGM) and into the Holocene. It is believed that the Southern Hemi-sphere Westerlies (SHW) play a key role in regulating climate change in the mid-to-high latitudes of the SH, thus reconstructing the SHW latitudinal positioning since the LGM has been crucial. However, terrestrial records of the mid-to-high latitudes are sparse. Most of the evidence is generally constrained to southern South America and New Zealand, and at times reveals contradictory results. Scientists have been trying to obtain a clearer picture of shifts in the SHW in the mid-to-high latitudes through analyzing terrestrial records from the island groups that make up the sub-Antarctic region. Here, a c.14000 cal yr BP terrestrial record from Port Douzieme (P12) at Iles Kerguelen (49°S) is analyzed using a multi-proxy approach (lithostratigraphy, magnetic susceptibility, loss on ignition, and pollen). The P12 record reveals clear changes since c.14000 cal yr BP, at which time a sparsely vegetated environ-ment existed, dominated by grasses (Poaceae). Then, the wind tolerant, cushion plant Azorella selago became a much more influential species by c.13600, coinciding with the presence of lacustrine-type-sediments, suggesting windier and wetter conditions. By c.12900 cal yr BP the lowland species Acaena magellanica suddenly expanded, becoming the dominant species and coinciding with the end of the Antarctic Cold Reversal (ACR). Finally, at c.11200 cal yr BP the species Uncinia compacta and Blechnum penna-marina appear in the pollen record, suggest-ing much warmer conditions on the Kerguelen archipelago. The record from P12 was compared with a previous study done by Van der Putten et al. (submitted) at the Estacade site in the Kerguelen archipelago, approximately 50 km northeast of the P12 site. The pollen record from the Estacade site shows a similar vegetation history as the rec-ord from P12 for the Kerguelen archipelago. At the Estacade site, Poaceae is prominent between c.16000-13650 cal yr BP, followed by a period of dominance by the wind tolerant species Azorella selago and Lyallia kerguelensis at 13650 cal yr BP. At around 11200 cal yr BP the lowland species Acaena magellanica and Uncinia compacta ex-panded. Additionally, the pollen record from P12 reveals a higher influence of the SHW at about 13600 cal yr BP, when a great diversity in long distance pollen grains is recorded, coinciding with the expansion of the wind tolerant species Azorella selago, as well as the presence of lacustrine-type-sediments at both the Estacade site and P12.},
  author       = {Henao, Victor},
  language     = {eng},
  note         = {Student Paper},
  series       = {Dissertations in Geology at Lund University},
  title        = {A palaeoenvironmental study of a peat sequence from Iles Kerguelen (49°S, Indian Ocean) for the Last Deglaciation based on pollen analysis},
  year         = {2015},
}