Antarctic Intermediate Water Variability and the Bi-polar Seesaw

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Title
Antarctic Intermediate Water Variability and the Bi-polar Seesaw

CoPED ID
4214e3dd-bcd5-43e3-9823-0b4e336a48e8

Status
Closed

Funders

Value
£106,594

Start Date
March 31, 2011

End Date
Sept. 19, 2013

Description

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Climate change during glacial and deglacial periods was dominated by rapid variations on a millennial time-scale. A central, but as yet poorly understood element of this millennial-scale climate change behavior is an asynchronous phasing of climate between the poles [Blunier et al., 1998], known as the 'bi-polar seesaw'. It is likely that the variability in intensity of intermediate flow from high to low latitudes is closely linked to these climate changes in the polar regions (sensu [Stott et al., 2007]). Computer simulations also suggest that variations in intermediate water circulation are intricately coupled to climate change in the polar regions' [Broecker, 1998; Stocker and Johnsen, 2003; Sijp and England, 2006]. Whilst there is growing recognition of the importance of intermediate water circulation for the bi-polar seesaw, millennial-scale variations in intermediate water circulation in crucial parts of the world ocean are not known. We are interested in the history of southern sourced intermediate waters (Antarctic Intermediate Water - AAIW) in the Indian Ocean. The role of GAAIW in the bi-polar seesaw is of global relevance due to its large volume and associated energy storage capacity. In the Indian Ocean, results of a New Investigators project (by the PI) provided insights into the short-term surface- and intermediate water variability recorded in the Arabian Sea. Surface ocean records from core NIOP 905 from the Arabian Sea imply a direct in-phase relation of monsoonal change with the well-known Dansgaard-Oeschger events in the N-Atlantic [Ivanochko et al., 2005] in line with previous results [Altabet et al., 2002; Schulz et al., 1998]. Striking new results are that 1) surface ocean and intermediate depth changes occur out-of-phase and 2) the intermediate water variability shows a close relation with Antarctic climate history, hence hosting evidence for a bi-polar seesaw pattern. Whilst the surface ocean change reflects Northern Hemisphere climate change, the intermediate water record seems to be tied to that in the south. This implies a climate connection between the high and low latitudes most likely mediated by variations in glacial AAIW (GAAIW) strength, with GAAIW enhancements occurring during the HE's, opposite to the N-Atlantic record of overturning circulation (figure 1). A locally derived signal for core NIOP 905, however, cannot be ruled out at this stage and additional research in a more southern position is required. Here we propose to utilize high-quality sediment core 64PE304-80 from the Mozambique Channel. This core is particularly suited for paleoceanographic work because it combines a very high sedimentation rate (~25 cm/ka), excellent carbonate preservation and a crucial location, allowing to trace surface and intermediate water changes at the millennial-scale. We aim to find evidence of increased GAAIW in the Channel to verify the wider significance of the Arabian Sea results, and the surface ocean data will help unravel the Indo-Atlantic surface water exchange (passing through the Channel) via the Agulhas system, which is a crucial component of Earth's climate [Peeters et al., 2004].

Simon Jung PI_PER
Dick Kroon COI_PER

Subjects by relevance
  1. Climate changes
  2. Climate
  3. Polar regions
  4. Water
  5. Deglaciation
  6. Atmosphere (earth)
  7. Change

Extracted key phrases
  1. Antarctic Intermediate Water Variability
  2. Intermediate water change
  3. Antarctic climate history
  4. Scale climate change behavior
  5. Intermediate water circulation
  6. Intermediate water record
  7. Intermediate water variability
  8. Intermediate depth change
  9. Northern Hemisphere climate change
  10. Surface ocean change
  11. Atlantic surface water exchange
  12. Polar seesaw pattern
  13. Climate change
  14. Polar Seesaw
  15. Polar region

Related Pages

UKRI project entry

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