Numerical modeling of the global semidiurnal tide in the present day and in the last glacial maximum

Egbert, G. D.; Ray, Richard D.; Bills, B. G.

doi:10.1029/2003jc001973

Cited by 272 publications

(437 citation statements)

References 41 publications

Supporting

Mentioning

407

Contrasting

Order By: Relevance

“…The loss of shallow shelf seas during the LGM has likely led to increased tidal energy dissipation in the deep ocean, which in turn may have caused enhanced vertical mixing (20,21). On the other hand, the increased deep ocean stratification during the LGM may have suppressed vertical mixing, as more turbulent kinetic energy dissipation would be required to mix the more stratified water column (22).…”

Section: Sensitivity Experimentsmentioning

confidence: 99%

Glacial ocean circulation and stratification explained by reduced atmospheric temperature

Jansen

2016

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Earth's climate has undergone dramatic shifts between glacial and interglacial time periods, with high-latitude temperature changes on the order of 5-10 • C. These climatic shifts have been associated with major rearrangements in the deep ocean circulation and stratification, which have likely played an important role in the observed atmospheric carbon dioxide swings by affecting the partitioning of carbon between the atmosphere and the ocean. The mechanisms by which the deep ocean circulation changed, however, are still unclear and represent a major challenge to our understanding of glacial climates. This study shows that various inferred changes in the deep ocean circulation and stratification between glacial and interglacial climates can be interpreted as a direct consequence of atmospheric temperature differences. Colder atmospheric temperatures lead to increased sea ice cover and formation rate around Antarctica. The associated enhanced brine rejection leads to a strongly increased deep ocean stratification, consistent with high abyssal salinities inferred for the last glacial maximum. The increased stratification goes together with a weakening and shoaling of the interhemispheric overturning circulation, again consistent with proxy evidence for the last glacial. The shallower interhemispheric overturning circulation makes room for slowly moving water of Antarctic origin, which explains the observed middepth radiocarbon age maximum and may play an important role in ocean carbon storage.LGM | AMOC | stratification | cooling | sea-ice T he deep ocean today is ventilated mainly by two water masses. North Atlantic deep water (NADW) is formed in the North Atlantic before flowing southward at a depth of about 2-3 km and eventually rising back up to the surface in the Southern Ocean. Antarctic bottom water (AABW) is formed around Antarctica and spreads northward into the abyssal basins. The AABW that makes it into the Atlantic then slowly upwells into the lower NADW before returning southward and resurfacing again around Antarctica (1, 2). The glacial equivalent of NADW was likely confined to shallower depths, leaving more of the deep Atlantic filled with water masses originating primarily from around Antarctica (3-5). Moreover, the two water masses appear more distinct, with less mixing between them (6).Multiple studies have pointed toward the potential importance of sea ice and surface buoyancy fluxes around Antarctica in controlling changes in the deep ocean stratification and circulation between the present and Last Glacial Maximum (LGM) (7-11). Specifically, we recently showed that enhanced buoyancy loss around Antarctica is expected to lead to an increase in the abyssal stratification, an upward shift of NADW, and a clearer separation between NADW and southward-flowing AABW (11)-all in agreement with inferences made for differences in circulation and stratification between the present and LGM (3,6,12,13). This gives rise to the hypothesis that strong cooling around Antarctica led to an increased net freezing...

show abstract

Section: Sensitivity Experimentsmentioning

confidence: 99%

Glacial ocean circulation and stratification explained by reduced atmospheric temperature

Jansen

2016

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…Based on the observation that mixing rates over rough topography are enhanced (Polzin et al 1997;Ledwell et al 2000) and inverse models of the tides that suggested enhanced energy loss from the barotropic tides over rough topography (Egbert and Ray 2000), Jayne and St. Laurent (2001) applied a parameterization for topographic drag in a model of the barotropic tides and found that it improved the simulated tides. This parameterization represents the physics of the conversion of tidal energy into internal wave energy and is similar to the topographic drag parameterization used in atmospheric models (Palmer et al 1986;McFarlane 1987).…”

mentioning

confidence: 99%

The Impact of Abyssal Mixing Parameterizations in an Ocean General Circulation Model

Jayne

2009

Journal of Physical Oceanography

199

166

View full text Add to dashboard Cite

A parameterization of vertical diffusivity in ocean general circulation models has been implemented in the ocean model component of the Community Climate System Model (CCSM). The parameterization represents the dynamics of the mixing in the abyssal ocean arising from the breaking of internal waves generated by the tides forcing stratified flow over rough topography. This parameterization is explored over a range of parameters and compared to the more traditional ad hoc specification of the vertical diffusivity.Diapycnal mixing in the ocean is thought to be one of the primary controls on the meridional overturning circulation and the poleward heat transport by the ocean. When compared to the traditional approach with uniform mixing, the new mixing parameterization has a noticeable impact on the meridional overturning circulation; while the upper limb of the meridional overturning circulation appears to be only weakly impacted by the transition to the new parameterization, the deep meridional overturning circulation is significantly strengthened by the change. The poleward ocean heat transport does not appear to be strongly affected by the mixing in the abyssal ocean for reasonable parameter ranges. The transport of the Antarctic Circumpolar Current through the Drake Passage is related to the amount of mixing in the deep ocean. The new parameterization is found to be energetically consistent with the known constraints on the ocean energy budget.

show abstract

“…Changes in sea level [e.g. likely altered the amount of tidal mixing, and in particular how tidal dissipation was partitioned between the continental shelves and the deep ocean [Egbert et al, 2004;Wunsch, 2005]. The degree to which changes in sea level may have changed the mixing within the ITF is unknown.…”

Section: Discussionmentioning

confidence: 99%

The centennial and millennial variability of the IndoPacific Warm Pool and the Indonesian Throughflow

Gibbons¹

2012

View full text Add to dashboard Cite

(Short version)As the only low-latitude connection between ocean basins, the Indonesian Throughflow allows the direct transmission of heat and salinity between the Pacific and Indian Oceans. The Mg/Ca and 6180 of calcite of Globigerinoides ruber (G. ruber) were used to estimate the sea surface temperature (SST) and 6180 of water, an indicator of hydrologic conditions, over the past 20,000 years. I also attempted to estimate thermocline structure using Pulleniatina obliquiloculata, but the Mg/Ca and 6180 of calcite data yield conflicting interpretations, indicating further work on this proxy is required. The G. ruber Mg/Ca results suggest that the SST of the outflow passages were influenced by high latitude Southern Hemisphere temperature. At approximately 10,000 years before present, there was a warming in the Makassar Strait. This local warming was coincident with the flooding of the Sunda Shelf, which opened a connection between the South China Sea and the Indonesian Throughflow. AbstractAs the only low-latitude connection between ocean basins, the Indonesian Throughflow allows the direct transmission of heat and salinity between the Pacific and Indian Oceans. Despite its potential importance, the role of the Indonesian Throughflow in global ocean circulation and regional climate is still not clear due to sparse measurements and the relative difficulty of modeling the region. The Mg/Ca and 6180 of calcite of the calcitic planktic foraminifera Globigerinoides ruber (G.ruber) were used to estimate the sea surface temperature and 6180 of water, an indicator of hydrologic conditions, over the past 20,000 years. I also attempted to estimate thermocline structure using the foraminifera, Pulleniatina obliquiloculata, AcknowledgementsWhile there is certainly a sense of relief to be finishing my thesis, it is also bittersweet. It will be extremely difficult for me to leave behind my good friends and colleagues.I could not ask for a better advisor (and friend and mentor) than Delia Oppo. Her commitment to her students, family, and science is an inspiration. She is extremely patient, and was always willing to let me do things my way, though I would have likely finished my degree two years early had I just listened to her in the first place. I did listen to her regarding family, when she told me, "By the time you want children, it will be too late." My son and I are particularly grateful for this piece of advice.I owe a big thank you to my committee members. Bill Curry, Jake Gebbie, and Kerry Emanuel guided my research and helped me create a stronger thesis.I could not have finished without the help of Olivier Marchal. Olivier's eagerness to answer any question I had (and perhaps some I had not yet realized I had) was always appreciated. His willingness to read my thesis and chair my defense on 24 hours notice is a testament to his generosity.We are lucky to have excellent collaborators. Mahyar Mohtadi (University of Bremen) and Brad Linsley (LDEO) have provided excellent feedback on many drafts of this thesis....

show abstract

Numerical modeling of the global semidiurnal tide in the present day and in the last glacial maximum

Cited by 272 publications

References 41 publications

Glacial ocean circulation and stratification explained by reduced atmospheric temperature

Glacial ocean circulation and stratification explained by reduced atmospheric temperature

The Impact of Abyssal Mixing Parameterizations in an Ocean General Circulation Model

The centennial and millennial variability of the IndoPacific Warm Pool and the Indonesian Throughflow

Contact Info

Product

Resources

About