"Slowing the rate of flow of the AMOC (via reduced AABW production); which would cause the North Atlantic current to get hotter and carry more heat into the Arctic"
As i understand it, AMOC steals heat from the South and warms the North, decrease in AMOC would relatively cool the north (but the effect would be swamped by AGW ...)
sidd,
The bipolar seesaw hypothesis has been around for a number of years and indicates that the temperatures of the NH & SH are out of phase and linked (see the Wikipedia link below). This bipolar seesaw mechanism is not only influenced by discharges of fresh water (melt water) in high latitudes, but also by Agulhas Current Leakage from the Indian Ocean into the Atlantic Ocean, and by shifts in the Intertropical Convergence Zones (ITCZ), all of which can contribute to abrupt climate change as highlighted by Hansen et al 2015 (also by the references cited below)
https://en.wikipedia.org/wiki/Polar_see-sawThe first linked paper provides evidence supporting the "bipolar seesaw theory of abrupt climate change." "Theoretical models and observational data have long suggested that the Northern and Southern Hemisphere climates behave in a seesaw-like fashion: when the northern ocean warms, the southern ocean cools and vice versa."
Kyoung-nam Jo, Kyung Sik Woo, Sangheon Yi, Dong Yoon Yang, Hyoun Soo Lim, Yongjin Wang, Hai Cheng & R. Lawrence Edwards (17 April 2014), "Mid-latitude interhemispheric hydrologic seesaw over the past 550,000 years", Nature, Volume: 508, Pages: 378–382, doi:10.1038/nature13076
http://www.nature.com/nature/journal/v508/n7496/full/nature13076.htmlAbstract: "An interhemispheric hydrologic seesaw—in which latitudinal migrations of the Intertropical Convergence Zone (ITCZ) produce simultaneous wetting (increased precipitation) in one hemisphere and drying in the other—has been discovered in some tropical and subtropical regions. For instance, Chinese and Brazilian subtropical speleothem (cave formations such as stalactites and stalagmites) records show opposite trends in time series of oxygen isotopes (a proxy for precipitation variability) at millennial to orbital timescales, suggesting that hydrologic cycles were antiphased in the northerly versus southerly subtropics. This tropical to subtropical hydrologic phenomenon is likely to be an initial and important climatic response to orbital forcing. The impacts of such an interhemispheric hydrologic seesaw on higher-latitude regions and the global climate system, however, are unknown. Here we show that the antiphasing seen in the tropical records is also present in both hemispheres of the mid-latitude western Pacific Ocean. Our results are based on a new 550,000-year record of the growth frequency of speleothems from the Korean peninsula, which we compare to Southern Hemisphere equivalents. The Korean data are discontinuous and derived from 24 separate speleothems, but still allow the identification of periods of peak speleothem growth and, thus, precipitation. The clear hemispheric antiphasing indicates that the sphere of influence of the interhemispheric hydrologic seesaw over the past 550,000 years extended at least to the mid-latitudes, such as northeast Asia, and that orbital-timescale ITCZ shifts can have serious effects on temperate climate systems. Furthermore, our result implies that insolation-driven ITCZ dynamics may provoke water vapour and vegetation feedbacks in northern mid-latitude regions and could have regulated global climate conditions throughout the late Quaternary ice age cycles."
The linked Marino & Zahn (2015) reference (and first attached image) shows how Agulhas Leakage can interact with the AMOC to strengthen of the bipolar seesaw:
Gianluca Marino and Rainer Zahn (January 2015), "The Agulhas Leakage: the missing link in the interhemispheric climate seesaw?", Past Global Changes Magazine, SCIENCE HIGHLIGHTS: Glacial terminations and interglacials
http://www.pages-igbp.org/download/docs/magazine/2015-1/PAGESmagazine_2015(1)_22-23_Marino.pdfExtract: "The Agulhas Leakage is a key component of the Atlantic Meridional Overturning Circulation. Unraveling the past patterns of leakage variability and associated heat and salt anomalies into the Atlantic Ocean holds clues for their role in ocean and climate changes."
The next linked reference (with a free access pdf, & see the second attached image) indicates that the leakage of warm saline water from the Agulhas Current into the Atlantic Ocean (see attached image), caused a positive feedback mechanism contributing to polar amplification during the Eemian; and that this mechanism could become increasingly important with increasing global warming today:
Turney, C. S.M. and Jones, R. T. (2010), Does the Agulhas Current amplify global temperatures during super-interglacials?. J. Quaternary Sci., 25: 839–843. doi: 10.1002/jqs.1423
http://onlinelibrary.wiley.com/doi/10.1002/jqs.1423/fullAbstract: "Future projections of climate suggest our planet is moving into a ‘super-interglacial’. Here we report a global synthesis of ice, marine and terrestrial data from a recent palaeoclimate equivalent, the Last Interglacial (ca. 130–116 ka ago). Our analysis suggests global temperatures were on average ∼1.5°C higher than today (relative to the AD 1961–1990 period). Intriguingly, we identify several Indian Ocean Last Interglacial sequences that suggest persistent early warming, consistent with leakage of warm, saline waters from the Agulhas Current into the Atlantic, intensifying meridional ocean circulation and increasing global temperatures. This mechanism may have played a significant positive feedback role during super-interglacials and could become increasingly important in the future. These results provide an important insight into a future 2°C climate stabilisation scenario."
The next linked reference documents the bipolar seesaw control during the last interglacial period:
G. Marino, E. J. Rohling, L. Rodríguez-Sanz, K. M. Grant, D. Heslop, A. P. Roberts, J. D. Stanford & J. Yu (11 June 2015), "Bipolar seesaw control on last interglacial sea level", Nature, Volume: 522, Pages: 197–201, doi:10.1038/nature14499
http://www.nature.com/nature/journal/v522/n7555/full/nature14499.htmlAbstract: "Our current understanding of ocean–atmosphere–cryosphere interactions at ice-age terminations relies largely on assessments of the most recent (last) glacial–interglacial transition, Termination I (T-I). But the extent to which T-I is representative of previous terminations remains unclear. Testing the consistency of termination processes requires comparison of time series of critical climate parameters with detailed absolute and relative age control. However, such age control has been lacking for even the penultimate glacial termination (T-II), which culminated in a sea-level highstand during the last interglacial period that was several metres above present. Here we show that Heinrich Stadial 11 (HS11), a prominent North Atlantic cold episode, occurred between 135 ± 1 and 130 ± 2 thousand years ago and was linked with rapid sea-level rise during T-II. Our conclusions are based on new and existing6, data for T-II and the last interglacial that we collate onto a single, radiometrically constrained chronology. The HS11 cold episode punctuated T-II and coincided directly with a major deglacial meltwater pulse, which predominantly entered the North Atlantic Ocean and accounted for about 70 per cent of the glacial–interglacial sea-level rise. We conclude that, possibly in response to stronger insolation and CO2 forcing earlier in T-II, the relationship between climate and ice-volume changes differed fundamentally from that of T-I. In T-I, the major sea-level rise clearly post-dates Heinrich Stadial 1. We also find that HS11 coincided with sustained Antarctic warming, probably through a bipolar seesaw temperature response12, and propose that this heat gain at high southern latitudes promoted Antarctic ice-sheet melting that fuelled the last interglacial sea-level peak."
The last linked reference discusses how Antarctic ice mass loss during Meltwater Pulse 1A reduced Southern Ocean overturning (including the AMOC), thus contributing to warming
N. R. Golledge, L. Menviel, L. Carter, C. J. Fogwill, M. H. England, G. Cortese & R. H. Levy, (2014), "Antarctic contribution to meltwater pulse 1A from reduced Southern Ocean overturning", Nature Communications, 5, Article number: 5107, doi:10.1038/ncomms6107
http://www.nature.com/ncomms/2014/140929/ncomms6107/abs/ncomms6107.htmlAbstract: "During the last glacial termination, the upwelling strength of the southern polar limb of the Atlantic Meridional Overturning Circulation varied, changing the ventilation and stratification of the high-latitude Southern Ocean. During the same period, at least two phases of abrupt global sea-level rise—meltwater pulses—took place. Although the timing and magnitude of these events have become better constrained, a causal link between ocean stratification, the meltwater pulses and accelerated ice loss from Antarctica has not been proven. Here we simulate Antarctic ice sheet evolution over the last 25 kyr using a data-constrained ice-sheet model forced by changes in Southern Ocean temperature from an Earth system model. Results reveal several episodes of accelerated ice-sheet recession, the largest being coincident with meltwater pulse 1A. This resulted from reduced Southern Ocean overturning following Heinrich Event 1, when warmer subsurface water thermally eroded grounded marine-based ice and instigated a positive feedback that further accelerated ice-sheet retreat."
Again, I note that all of this supports the Hansen et al 2015 findings.
Very best,
ASLR
Edit: Note that in the first attached image that when the Southern Ocean Subtropical Front moves northward (say by 2040 due to the initial of a main phase collapse of the WAIS) the Agulhas Leakage is reduced, which would help warm the North Atlantic (in a bipolar seesaw manner)