Antarctic ocean tide changes since LGM

Egbert, Gary D., Richard D. Ray, and Bruce G. Bills. "Numerical modeling of the global semidiurnal tide in the present day and in the last glacial maximum." Journal of Geophysical Research: Oceans 109.C3 (2004).

 

Arbic, Brian K., et al. "Palaeoclimate: Ocean tides and Heinrich events." Nature 432.7016 (2004): 460.

 

Griffiths, Stephen D., and W. Richard Peltier. "Modeling of polar ocean tides at the Last Glacial Maximum: Amplification, sensitivity, and climatological implications." Journal of Climate22.11 (2009): 2905-2924.

 

Wilmes, S‐B., and J. A. M. Green. "The evolution of tides and tidal dissipation over the past 21,000 years." Journal of Geophysical Research: Oceans 119.7 (2014): 4083-4100.

 

Schmittner, A., J. A. M. Green, and S‐B. Wilmes. "Glacial ocean overturning intensified by tidal mixing in a global circulation model." Geophysical Research Letters 42.10 (2015): 4014-4022.

Paleo tidal modeling

• in principal straight forward
• tide generating force is well known
• solved on water column thickness grid

https://www.youtube.com/watch?v=x7GXLJQ2Zn0

Tide model sensitivities

Tidal solution sensitive to:

• ice sheet grounding lines
• mean global sea level
• earth response to ice sheet loading

(Wilmes & Green, 2014)

M2 amplitudes for (a) floating and (b) grounded Antarctic ice shelves

LGM tidal height amplitudes

 

• near resonant excitation (some studies more than 3x)
• M2 large changes (~2x)
• K1 small changes
• studies disagree about Arctic 'megatites' (more than 4x)

(Griffiths & Peltier, 2009)

https://journals.ametsoc.org/doi/pdf/10.1175/2008JCLI2540.1

http://onlinelibrary.wiley.com/doi/10.1002/2013JC009605/epdf

(Wilmes & Green, 2014)

http://onlinelibrary.wiley.com/doi/10.1029/2003JC001973/full

(Egbert et al., 2004)

LGM tidal dissipation

• amplified LGM tides lead to increased total dissipation (M2 ~50% larger)
• shift of main location from shallow to deep
• shift of main mechanism from bottom friction to internal tide

(e.g. Egbert et al., 2004; Wilmes and Green, 2014)

M2 present

M2 LGM

http://people.oregonstate.edu/~schmita2/pdf/S/schmittner15grl.pdf

(Schmittner et al., 2015)

(Wilmes and Green, 2014)

M2 dissipation for (left) PD and (right) LGM

LGM to PD transition

 

• nonlinear transition
• strongly tied to ice sheet extend and sea level
• regional differences in timing and magnitude

(Wilmes and Green, 2014)

Ocean tides and Heinrich events

 

• tidal flexure at grounding zone weakens ice shelf
• ice sheet-tide interaction could control ice front position or ice shelf advance-disintegration cycle
• past large tides may have controlled Heinrich Events  

https://www.nature.com/articles/432460a.pdf

(Arbic et al., 2004)

(Griffiths et al., 2009)

Ice shelf tidal flexure

Ocean tides and the MOC

 

• internal wave breaking causes vertical mixing
• tides-sea ice interaction impact surface heat and salt flux
• tides in weddell sea impact AABW formation
• enhanced LGM tidal mixing strengthens MOC (21-46%) 

M2 present

http://people.oregonstate.edu/~schmita2/pdf/S/schmittner15grl.pdf

Robertson, Robin, Laurie Padman, and Gary D. Egbert. "Tides in the Weddell Sea." Ocean, ice, and atmosphere: interactions at the Antarctic Continental Margin (1998): 341-369.

(Robertson et al., 1998)

(Robertson et al., 1998)

(Schmittner et al., 2015)

Ocean tides and basal mass loss