This is a list of quotes to “sloshing” as applied to ENSO

http://www.nc-climate.ncsu.edu/climate/patterns/ENSO.html
The El Niño-Southern Oscillation (ENSO) is a naturally occurring phenomenon that involves fluctuating ocean temperatures in the equatorial Pacific. The warmer waters essentially slosh, or oscillate, back and forth across the Pacific, much like water in a bath tub.

http://www.climate.gov/news-features/featured-images/slow-slosh-warm-water-across-pacific-hints-el-ni%C3%B1o-brewing
Slow slosh of warm water across Pacific hints El Niño is brewing

http://news.sciencemag.org/climate/2014/08/ancient-piles-clams-reveal-peek-el-ni-os-past
The phenomenon in question is the El Niño–Southern Oscillation, or ENSO, a global climatic cycle that affects both sides of the tropical Pacific Ocean and beyond. During its warm phase, called El Niño, warm water sloshes from the west side of the Pacific to the east side, where it brings warmth and rain to the Americas.

http://blogs.nicholas.duke.edu/thegreengrok/el-nino-la-nina-and-global-warming/
To understand what the El Nino-Southern Oscillation or ENSO is about, you should think of the tropical Pacific Ocean as a huge bathtub with water sloshing back and forth. But a bathtub with an important characteristic: in this tub, the surface water at the western end (near Indonesia and Australia) tends to be warm while the water on the eastern end (near South America) tends to be cool.

Nonlinear Dynamics in Geosciences (Google eBook)

This model underscores two important elements for the recurrent occurrence of El Niño events which result in repeatedly “sloshing” of water in the equatorial upper ocean.

http://iridl.ldeo.columbia.edu/maproom/ENSO/New/wyrtki.html
Taking advantage of a network of tide gauges in the tropical Pacific, Wyrtki compiled an extensive record of sea levels. In the tropics, monthly average sea level is an excellent substitute for the monthly average depth of the thermocline — that is, for the thickness of the upper ocean warm layer. Wyrtki showed that a transfer of warm water from west to east pushes down the thermocline deeper in the ocean, triggering the warm phase (El Niño) of ENSO.
A simple way to visualize the transfer of ocean water from west to east (and vice versa) is to think of the tropical Pacific as a huge tub, with the waters sloshing back and forth. This sloshing precedes a shift in the ENSO state.
Preceding an El Niño, this sloshing leads to higher sea levels in the eastern Pacific, for example at the Peruvian coast. Using the sloshing bathtub as a guide, this means that they must be low in the western Pacific, for example eastern Australia. With the warming in the eastern Pacific, the Bjerkness positive feedback takes over: the winds weaken and still more warm water flows east and SSTs warm. The main center of atmospheric convection shifts eastward, disrupting the world’s “normal” weather patterns. Eventually, after about 6-18 months, this water will slosh back west and set off the next ENSO event.

http://www.esrl.noaa.gov/psd/people/dezheng.sun/dspapers/enso-meanclimate/Sun-final-1.pdf
We first describe some phenomenological aspects of ENSO and highlight the fact that ENSO corresponds to a basin-wide “sloshing” of the water in the equatorial upper Pacific

http://www.earthgauge.net/wp-content/CF_Oscillations%20and%20Teleconnections.pdf
Probably the best known of Earth’s regular oscillations, ENSO is essentially the “sloshing” back and forth of warm water between the eastern and western tropical Pacific.

http://www.wmo.int/pages/themes/climate/significant_natural_climate_fluctuations.php
The net effect of these interactions gives the appearance of large quantities of warm water slowly sloshing back and forth across the equatorial Pacific and a large east-west oscillation in the heat supply to the atmosphere from the Pacific Ocean. At the peak of an El Niño event, the tropical Pacific Ocean is warmer than normal and the global near-surface air temperature warms up as the ocean gives up heat to the atmosphere.

Technical references on sloshing: