Dear AbruptSLR
All these links are very interesting and somewhat very worrying considering the complacency of our policymakers...
Would it be possible to get a physical explanation of how the teleconnection between a strong El Nino and a stronger pulse of relatively warm water in CDW ? Maybe it is already explained somewhere in the forum, but I, unfortunately, have not been able to find it
Is there any paper quantifying the increase of warm water pulse based on modelled projection of higher frequency and stronger El Nino event? And, sorry maybe it is a very basic question, from which process global warming will increase the frequenwy of El Nino and SAM?
Is there any potential link between the slow down of AMOC and the Antarctica, or is it too far fetched as deep water takes quite some time to go back to the South hemisphere?
Thanks
bluesky,
Basically, the top elevation of the circumpolar deep water, CDW, is typically just below deep troughs in the continental shelf of the Amundsen Sea Embayment, ASE. Further the Amundsen Bellingshausen Sea Low, ABSL (or ASL) & see the first image), is a frequent low pressure atmospheric system that moves east-west along the Amundsen – Bellingshausen Seas coastline, depending on numerous atmospheric conditions, but predominately by the combination of the ENSO & SAM (see the second & third images), due to the teleconnection of atmospheric energy by Rossby Waves from the Tropical Pacific Ocean. When in the correct position, the ABSL blows wind into the ASE which drags the surface ocean water with it; which in turn causes upwelling of the CDW into the deep troughs which, all lead to the grounding lines of the various ASE marine glaciers.
The AMOC slowdown can impact the ENSO via atmospheric telecommunication from the Atlantic to the Pacific basins, depending on the season and other metocean conditions.
Also see:
The thread entitled: "Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Time Frame":
From Reply #75:
The following linked article supports the point that in a big El Nino year both PIIS and PIG will lose ice more rapidly than normal:
http://www.science20.com/news_articles/antarcticas_pine_island_glacier_melt_blame_el_nino-127129From Reply #76:
To those who would like access to the source material for the information cited in my immediate past post, please see the following links, abstract, and related references:
http://www.sciencemag.org/content/early/2014/01/02/science.1244341.abstracthttp://www.sciencemag.org/content/suppl/2014/01/02/science.1244341.DC1/Dutrieux.SM.pdfPierre Dutrieux, Jan De Rydt, Adrian Jenkins, Paul R. Holland, Ho Kyung Ha, Sang Hoon Lee, Eric J. Steig, Qinghua Ding, E. Povl Abrahamsen, and Michael Schröder, 2014, "Strong Sensitivity of Pine Island Ice-Shelf Melting to Climatic Variability", Science; Published online 2 January 2014 [DOI:10.1126/science.1244341]
Abstract:
"Pine Island Glacier has thinned and accelerated over recent decades, significantly contributing to global sea-level rise. Increased oceanic melting of its ice shelf is thought to have triggered those changes. Observations and numerical modeling reveal large fluctuations in the ocean heat available in the adjacent bay and enhanced sensitivity of ice shelf melting to water temperatures at intermediate depth, as a seabed ridge blocks the deepest and warmest waters from reaching the thickest ice. Oceanic melting decreased by 50% between January 2010 and 2012, with ocean conditions in 2012 partly attributable to atmospheric forcing associated with a strong La Niña event. Both atmospheric variability and local ice shelf and seabed geometry play fundamental roles in determining the response of the Antarctic Ice Sheet to climate."
Supplemental references:
1. S. S. Jacobs, A. Jenkins, H. Hellmer, C. Giulivi, F. Nitsche, B. Huber, R. Guerrero, The
Amundsen Sea and the Antarctic Ice Sheet. Oceanography 25, 154–163 (2012).
doi:10.5670/oceanog.2012.90
2. S. S. Jacobs, A. Jenkins, C. F. Giulivi, P. Dutrieux, Stronger ocean circulation and increased
melting under Pine Island Glacier ice shelf. Nat. Geosci. 4, 519–523 (2011).
doi:10.1038/ngeo1188
3. S. S. Jacobs, H. H. Hellmer, A. Jenkins, Antarctic Ice Sheet melting in the southeast Pacific.
Geophys. Res. Lett. 23, 957–960 (1996). doi:10.1029/96GL00723
4. A. Jenkins, P. Dutrieux, S. S. Jacobs, S. D. McPhail, J. R. Perrett, A. T. Webb, D. White,
Observations beneath Pine Island Glacier in West Antarctica and implications for its
retreat. Nat. Geosci. 3, 468–472 (2010). doi:10.1038/ngeo890
5. D. J. Wingham, D. W. Wallis, A. Shepherd, Spatial and temporal evolution of Pine Island
Glacier thinning, 1995–2006. Geophys. Res. Lett. 36, L17501 (2009).
doi:10.1029/2009GL039126
6. A. Shepherd, E. R. Ivins, G. A, V. R. Barletta, M. J. Bentley, S. Bettadpur, K. H. Briggs, D. H.
Bromwich, R. Forsberg, N. Galin, M. Horwath, S. Jacobs, I. Joughin, M. A. King, J. T.
Lenaerts, J. Li, S. R. Ligtenberg, A. Luckman, S. B. Luthcke, M. McMillan, R. Meister,
G. Milne, J. Mouginot, A. Muir, J. P. Nicolas, J. Paden, A. J. Payne, H. Pritchard, E.
Rignot, H. Rott, L. S. Sørensen, T. A. Scambos, B. Scheuchl, E. J. Schrama, B. Smith, A.
V. Sundal, J. H. van Angelen, W. J. van de Berg, M. R. van den Broeke, D. G. Vaughan,
I. Velicogna, J. Wahr, P. L. Whitehouse, D. J. Wingham, D. Yi, D. Young, H. J. Zwally,
A reconciled estimate of ice-sheet mass balance. Science 338, 1183–1189 (2012).
Medline doi:10.1126/science.1228102
7. E. Rignot, Changes in West Antarctic ice stream dynamics observed with ALOS PALSAR
data. Geophys. Res. Lett. 35, L12505 (2008). doi:10.1029/2008GL033365
8. I. Joughin, E. Rignot, C. E. Rosanova, B. K. Lucchitta, J. Bolhander, Timing of Recent
Accelerations of Pine Island Glacier, Antarctica. Geophys. Res. Lett. 30, 1706 (2003).
doi:10.1029/2003GL017609
9. I. Joughin, B. E. Smith, D. M. Holland, Sensitivity of 21st century sea level to ocean-induced
thinning of Pine Island Glacier, Antarctica. Geophys. Res. Lett. 37, L20502 (2010).
doi:10.1029/2010GL044819
10. H. D. Pritchard, S. R. Ligtenberg, H. A. Fricker, D. G. Vaughan, M. R. van den Broeke, L.
Padman, Antarctic ice-sheet loss driven by basal melting of ice shelves. Nature 484, 502–
505 (2012). Medline doi:10.1038/nature10968
11. A. Shepherd, D. Wingham, D. Wallis, K. Giles, S. Laxon, A. V. Sundal, Recent loss of
floating ice and the consequent sea level contribution. Geophys. Res. Lett. 37, L13503
(2010). doi:10.1029/2010GL042496
12. A. Shepherd, D. Wingham, E. Rignot, Warm ocean is eroding West Antarctic Ice Sheet.; Geophys. Res. Lett. 31, L23402 (2004). doi:10.1029/2004GL021106
From Reply #131:
The linked reference (the second link has a free pdf) ties the warming of the Tropical Atlantic SST to a strengthening of both the Antarctic Circumpolar Winds and the Amundsen Bellingshausen Sea Low (ABSL/ASL) via atmospheric Rossby waves in all seasons except the austral summer. The conclusions of this paper (see the extract below) recommends that efforts be made to inter-relate this Atlantic tropical-Antarctic teleconnection with other tropical teleconnections (such as those identified by Fogt et al 2011, see the first attached image relating El Nino events & negative Southern Annular Mode, SAM, conditions that promote teleconnection of Tropical Pacific energy towards the Amundsen Sea Embayment, via atmospheric Rossby wave-trains). As we are now likely approaching very strong El Nino conditions by October 2015, it will be very interesting to see whether both the Tropical Atlantic and the Tropical Pacific soon teleconnect large amounts of atmospheric energy into Western Antarctica.
Additionally, the second attached image today from the Earth nullschool shows that the ABSL is relatively strong (i.e. has a relatively low central pressure) and is currently directing energy directly into the Amundsen Sea Embayment, ASE.
XICHEN LI, EDWIN P. GERBER, DAVID M. HOLLAND, AND CHANGHYUN YOO, (2015), "A Rossby Wave Bridge from the Tropical Atlantic to West Antarctica", J. Climate, 28, 2256–2273, doi:
http://dx.doi.org/10.1175/JCLI-D-14-00450.1 http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00450.1http://polarmet.osu.edu/ACCIMA/li_gerber_jc_2015.pdfAbstract: "Tropical Atlantic sea surface temperature changes have recently been linked to circulation anomalies around Antarctica during austral winter. Warming in the tropical Atlantic associated with the Atlantic multidecadal oscillation forces a positive response in the southern annular mode, strengthening the Amundsen–Bellingshausen Sea low in particular. In this study, observational and reanalysis datasets and a hierarchy of atmospheric models are used to assess the seasonality and dynamical mechanism of this teleconnection. Both the reanalyses and models reveal a robust link between tropical Atlantic SSTs and the Amundsen–Bellingshausen Sea low in all seasons except austral summer. A Rossby wave mechanism is then shown to both explain the teleconnection and its seasonality. The mechanism involves both changes in the excitation of Rossby wave activity with season and the formation of a Rossby waveguide across the Pacific, which depends critically on the strength and extension of the subtropical jet over the west Pacific. Strong anticyclonic curvature on the poleward flank of the jet creates a reflecting surface, channeling quasi-stationary Rossby waves from the subtropical Atlantic to the Amundsen–Bellingshausen Sea region. In summer, however, the jet is weaker than in other seasons and no longer able to keep Rossby wave activity trapped in the Southern Hemisphere. The mechanism is supported by integrations with a comprehensive atmospheric model, initial-value calculations with a primitive equation model on the sphere, and Rossby wave ray tracing analysis."
Extract: "Antarctic climate is also influenced by other tropical–polar teleconnections (Fogt et al. 2011; Ding et al. 2012), and key questions remain concerning the relative importance of these effects. The time scales of tropical SST variability differs significantly from one region to another (e.g., ENSO and the east Pacific dominate on interannual time scales, while the AMO and Pacific decadal oscillation are more significant on longer time scales). Moreover, SSTs in different tropical ocean basins may interact with each other through tropical ocean interbasin teleconnections. It is thus important to further investigate the relative importance and the relationship between the teleconnections from different tropical ocean sectors as a function of time scale."
Also see the thread entitled: "Risks and Challenges for Regional Circulation Models of the Southern Ocean"
From Reply #51:
It has been a while since I posted the attached figure from Bertler et al 2006 (see reference at bottom of this post), which shows pictorially the relationship between the location of the Amundsen Sea Low (or Amundsen Bellingshausen Sea Low), ASL (or ABSL) and either a La Nina or an El Nino event. Taken together with the information in my immediately preceding post (which stated that sea surface warming related to the Atlantic Multidecadal Oscillation, AMO, reduces the surface pressure in the Amundsen Sea), this implies that when the next El Nino event occurs (which may be the austral summer of 2014 to 2015) and shifts the location of the ASL to blow wind directly into the ASE, the winds will likely be stronger due to the lower Amundsen sea pressure associated with AMO effect; which will drive more warm CDW into the ASE resulting in higher than previously expected ice mass loss from the glaciers in this area.
Bertler, N.A., Naish, T.T., Mayewski, P.A. and Barrett, P.J., (2006), "Opposing oceanic and atmospheric ENSO influences on the Ross Sea Region, Antarctica", Advances in Geosciences, 6, pp 83-88, SRef-ID: 1680-7359/adgeo/2006-6-83.