Editing Seiche (section)

==Occurrence==
Seiches have been observed on both lakes and seas. The key requirement is that the body of water be partially constrained to allow formation of standing waves. Regularity of geometry is not required; even harbours with exceedingly irregular shapes are routinely observed to oscillate with very stable frequencies.

===Lake seiches===
Low rhythmic seiches are almost always present on larger lakes. They are usually unnoticeable among the common wave patterns, except during periods of unusual calm. [[Harbour]]s, bays, and [[estuaries]] are often prone to small seiches with amplitudes of a few centimetres and periods of a few minutes.

The original studies in [[Lake Geneva]] by [[François-Alphonse Forel]] found the longitudinal period to have a 73-minute cycle, and the transversal seiche to have a period of around 10 minutes.<ref>{{Citation|last=Lemmin|first=Ulrich|title=Surface Seiches |date=2012|encyclopedia=Encyclopedia of Lakes and Reservoirs|pages=751–753|editor-last=Bengtsson|editor-first=Lars|publisher=Springer Netherlands|language=en|doi=10.1007/978-1-4020-4410-6_226|isbn=978-1-4020-4410-6|editor2-last=Herschy|editor2-first=Reginald W.|editor3-last=Fairbridge|editor3-first=Rhodes W.|series=Encyclopedia of Earth Sciences Series}}</ref> Another lake well known for its regular seiches is New Zealand's [[Lake Wakatipu]], which varies its surface height at [[Queenstown, New Zealand|Queenstown]] by 20 centimetres in a 27-minute cycle. Seiches can also form in semi-enclosed seas; the [[North Sea]] often experiences a lengthwise seiche with a period of about 36 hours.
[[Image:Lake Erie water level.gif|thumb|right|450px|Differences in water level caused by a seiche on [[Lake Erie]], recorded between [[Buffalo, New York]] (''red'') and [[Toledo, Ohio]] (''blue'') on November 14, 2003]]

The [[National Weather Service]] issues low water advisories for portions of the Great Lakes when seiches of {{convert|2|ft|m|order=flip|sigfig=1}} or greater are likely to occur.<ref>{{cite web|last1=Pierce|first1=T.|title=Marine and Coastal Services Abbreviations and Definitions|url=http://www.weather.gov/directives/sym/pd01003001curr.pdf|publisher=[[National Weather Service]], Office of Climate, Water, and Weather Services|access-date=April 19, 2017|archive-url=https://web.archive.org/web/20080517023653/http://www.weather.gov/directives/sym/pd01003001curr.pdf|archive-date=May 17, 2008|date=July 5, 2006}}</ref> [[Lake Erie]] is particularly prone to wind-caused seiches because of its shallowness and its elongation on a northeast–southwest axis, which frequently matches the direction of prevailing winds and therefore maximises the [[Fetch (geography)|fetch]] of those winds. These can lead to extreme seiches of up to {{convert|5|m|ft}} between the ends of the lake.

The effect is similar to a [[storm surge]] like that caused by hurricanes along ocean coasts, but the seiche effect can cause oscillation back and forth across the lake for some time. In 1954, the remnants of [[Hurricane Hazel]] piled up water along the northwestern [[Lake Ontario]] shoreline near [[Toronto]], causing extensive flooding, and established a seiche that subsequently caused flooding along the south shore.

Lake seiches can occur very quickly: on July 13, 1995, a large seiche on [[Lake Superior]] caused the water level to fall and then rise again by one metre (three feet) within fifteen minutes, leaving some boats hanging from the docks on their mooring lines when the water retreated.<ref name="2000-02--umn">{{cite web |first=Ben |last=Korgen |url=http://www.seagrant.umn.edu/newsletter/2000/02/bonanza_for_lake_superior_seiches_do_more_than_move_water.html |title=Bonanza for Lake Superior: Seiches Do More Than Move Water
|publisher=[[University of Minnesota Duluth]] |website=seagrant.umn.edu |date=February 2000
|archive-url=https://web.archive.org/web/20071227044356/http://www.seagrant.umn.edu/newsletter/2000/02/bonanza_for_lake_superior_seiches_do_more_than_move_water.html |archive-date=2007-12-27 |url-status=dead}}
</ref> The same storm system that caused the 1995 seiche on Lake Superior produced a similar effect in [[Lake Huron]], in which the water level at [[Port Huron]] changed by {{convert|6|ft|m|1|order=flip}} over two hours.<ref>{{cite web|url=http://www.glerl.noaa.gov/seagrant/glwlphotos/Seiche/13July1995/13July1995Storm.html|title=Lake Huron Storm Surge July 13, 1995|publisher=NOAA|access-date=2009-03-13|archive-date=2008-09-16|archive-url=https://web.archive.org/web/20080916230039/http://www.glerl.noaa.gov/seagrant/glwlphotos/Seiche/13July1995/13July1995Storm.html|url-status=dead}}</ref> On June 26, 1954, on [[Lake Michigan]] in Chicago, eight fishermen were swept away from piers at Montrose and North Avenue Beaches and drowned when a {{convert|10|ft|m|adj=on|order=flip|0}} seiche hit the [[Chicago]] waterfront.<ref>{{cite news |title=Huge Lake Wave Hits Chicago; Four Drowned, Ten Are Missing |url=https://www.nytimes.com/1954/06/27/archives/huge-lake-wave-hits-chicago-four-drowned-ten-a-re-missing-huge-lake.html |work=The New York Times |issue=35218 |volume=103 |date=27 June 1954 |access-date=2 October 2021 |archive-date=2 October 2021 |archive-url=https://web.archive.org/web/20211002053715/https://www.nytimes.com/1954/06/27/archives/huge-lake-wave-hits-chicago-four-drowned-ten-a-re-missing-huge-lake.html |url-status=live }}</ref>

Lakes in seismically active areas, such as [[Lake Tahoe]] in [[California]]/[[Nevada]], are significantly at risk from seiches. Geological evidence indicates that the shores of Lake Tahoe may have been hit by seiches and tsunamis as much as {{convert|10|m|ft}} high in prehistoric times, and local researchers have called for the risk to be factored into emergency plans for the region.<ref>{{cite journal |last1=Brown |first1=Kathryn |title=Tsunami! At Lake Tahoe? |journal=Science News |date=10 June 2000 |volume=157 |issue=24 |pages=378–380 |url=https://dx.doi.org/10.2307/4012358|doi=10.2307/4012358|jstor=4012358 |url-access=subscription}}</ref>

[[Earthquake]]-generated seiches can be observed thousands of miles away from the epicentre of a quake. [[Swimming pools]] are especially prone to seiches caused by earthquakes, as the ground tremors often match the resonant frequencies of small bodies of water. The 1994 [[Northridge earthquake]] in [[California]] caused swimming pools to overflow across southern California.  The massive [[Good Friday earthquake]] that hit [[Alaska]] in 1964 caused seiches in swimming pools as far away as [[Puerto Rico]].<ref>{{cite web|url=https://www.soest.hawaii.edu/GG/ASK/seiche.html|title=Seiche|website=soest.hawaii.edu|access-date=2019-03-12|archive-date=2019-01-26|archive-url=https://web.archive.org/web/20190126040622/http://www.soest.hawaii.edu/GG/ASK/seiche.html|url-status=live}}</ref> The [[1755 Lisbon earthquake|earthquake that hit Lisbon, Portugal]] in 1755 also caused seiches {{convert|1300|mi|km|order=flip}} farther north in Loch Lomond, Loch Long, Loch Katrine and Loch Ness in [[Scotland]],<ref>{{cite web|title=Seismic Seiches|url=https://earthquake.usgs.gov/learn/topics/seiche.php|department=USGS Earthquake Hazards Program|publisher=Abridged from Earthquake Information Bulletin, January–February 1976, Volume 8, Number 1.|access-date=19 April 2017|archive-date=20 April 2017|archive-url=https://web.archive.org/web/20170420045540/https://earthquake.usgs.gov/learn/topics/seiche.php|url-status=live}}</ref> and in [[canal]]s in [[Sweden]]. The [[2004 Indian Ocean earthquake]] caused seiches in standing water bodies in many Indian states as well as in [[Bangladesh]], [[Nepal]], and northern [[Thailand]].<ref>In fact, "one person drowned in a pond as a result of a seiche in Nadia, West Bengal". {{cite web|title=26 December 2004, M9.1 "Boxing Day" Earthquake & Tsunami/Sumatra-Andaman Earthquake/Indian Ocean Tsunami|url=http://asc-india.org/lib/20041226-sumatra.htm|publisher=Amateur Seismic Centre|access-date=19 April 2017|location=Pune|date=22 Feb 2008|archive-date=21 January 2007|archive-url=https://web.archive.org/web/20070121074902/http://asc-india.org/lib/20041226-sumatra.htm|url-status=live}}</ref> Seiches were again observed in [[Uttar Pradesh]], [[Tamil Nadu]] and [[West Bengal]] in [[India]] as well as in many locations in [[Bangladesh]] during the [[2005 Kashmir earthquake]].<ref>{{cite web|url=http://asc-india.org/lib/20051008-kashkoh.htm|title=M7.6 Kashmir-Kohistan Earthquake, 2005|publisher=Amateur Seismic Centre|location=Pune|date=31 Oct 2008|access-date=19 April 2017|archive-date=6 June 2017|archive-url=https://web.archive.org/web/20170606080846/http://asc-india.org/lib/20051008-kashkoh.htm|url-status=live}}</ref>

The [[1950 Assam–Tibet earthquake]] is known to have generated seiches as far away as [[Norway]] and southern [[England]]. Other earthquakes in or near the Indian sub-continent known to have generated seiches include the [[1803 Garhwal earthquake|1803 Kumaon-Barahat]], [[1819 Rann of Kutch earthquake|1819 Allah Bund]], 1842 Central Bengal, [[1905 Kangra earthquake|1905 Kangra]], [[1930 Dhubri earthquake|1930 Dhubri]], [[1934 Nepal–India earthquake|1934 Nepal-Bihar]], [[2001 Bhuj earthquake|2001 Bhuj]], [[2005 Nias–Simeulue earthquake|2005 Nias]] and the 2005 Teresa Island earthquakes. The [[2010 Chile earthquake|February 27, 2010 Chile earthquake]] produced a seiche on [[Lake Pontchartrain]], [[Louisiana]], with a height of around {{convert|0.5|ft|mm|order=flip}}. The [[2010 Baja California earthquake]] produced large seiches that quickly became an internet phenomenon.<ref>{{cite web|url=http://arizonageology.blogspot.com/2010/04/video-of-mini-tsunami-in-devils-hole.html|title=Arizona Geology: Video of seiche in Devils Hole pupfish pond. (Posted: April 27, 2010)|access-date=17 October 2014|date=2010-04-27|archive-date=2014-12-19|archive-url=https://web.archive.org/web/20141219025100/http://arizonageology.blogspot.com/2010/04/video-of-mini-tsunami-in-devils-hole.html|url-status=live}}</ref>

Seiches up to at least 1.8 m (6&nbsp;feet) were observed in [[Sognefjorden]], [[Norway]], during the [[2011 Tōhoku earthquake]] in Japan.<ref>[http://www.sognavis.no/lokale_nyhende/article5528066.ece Fjorden svinga av skjelvet] (''tr. "The fjord swayed from the earthquake"'') {{webarchive|url=https://web.archive.org/web/20110318023743/http://www.sognavis.no/lokale_nyhende/article5528066.ece |date=2011-03-18 }} Retrieved on 2011-03-17.</ref><ref>{{cite web|url=https://arstechnica.com/science/2013/06/japanese-earthquake-literally-made-waves-in-norway/|title=Japanese earthquake literally made waves in Norway|first=Scott K.|last=Johnson|date=30 June 2013|website=Ars Technica|access-date=18 April 2019|archive-date=30 July 2022|archive-url=https://web.archive.org/web/20220730162534/https://arstechnica.com/science/2013/06/japanese-earthquake-literally-made-waves-in-norway/|url-status=live}}</ref>

===Sea and bay seiches===
Seiches have been observed in seas such as the [[Adriatic Sea]] and the [[Baltic Sea]]. This results in the flooding of [[Venice]] and [[Saint Petersburg]], respectively, as both cities are constructed on former marshland. In St. Petersburg, seiche-induced flooding is common along the [[Neva River]] in the autumn. The seiche is driven by a low-pressure region in the [[North Atlantic]] moving onshore, giving rise to [[cyclone|cyclonic]] lows on the [[Baltic Sea]]. The low pressure of the cyclone draws greater-than-normal quantities of water into the virtually landlocked Baltic. As the cyclone continues inland, long, low-frequency seiche waves with wavelengths up to several hundred kilometres are established in the Baltic. When the waves reach the narrow and shallow Neva Bay, they become much higher—ultimately flooding the Neva embankments.<ref>This behaves in a fashion similar to a [[tidal bore]] where incoming tides are funneled into a shallow, narrowing river via a broad bay. The funnel-like shape increases the height of the tide above normal, and the flood appears as a relatively rapid increase in the water level.</ref> Similar phenomena are observed at Venice, resulting in the [[MOSE Project]], a system of 79 mobile barriers designed to protect the three entrances to the [[Venetian Lagoon]].

In Japan, seiches have been observed in [[Nagasaki Bay]], most often in the spring.  During a seiche event on 31 March 1979, a water-level displacement of {{convert|2.78|m|ft}} was recorded at Nagasaki tide station; the maximum displacement in the whole bay is thought to have reached as much as {{convert|4.70|m|ft}}.  Seiches in Western [[Kyushu]]—including Nagasaki Bay—are often induced by a low in the atmospheric pressure passing South of Kyushu island.<ref>{{cite journal
  | doi = 10.1007/BF02110288
  | last = Hibiya
  | first = Toshiyuki
  | author2 = Kinjiro Kajiura
  | title = Origin of the ''Abiki'' Phenomenon (a kind of Seiche) in Nagasaki Bay
  | journal = Journal of Oceanographical Society of Japan
  | volume = 38
  | pages = 172–182
  | year = 1982
  | url = http://www.terrapub.co.jp/journals/JO/JOSJ/pdf/3803/38030172.pdf
  | access-date = 2009-02-26
  | issue = 3
  | bibcode = 1982JOce...38..172H
 | s2cid = 198197231
  | archive-date = 2011-05-27
  | archive-url = https://web.archive.org/web/20110527051123/http://www.terrapub.co.jp/journals/JO/JOSJ/pdf/3803/38030172.pdf
  | url-status = dead
  }}</ref> Seiches in Nagasaki Bay have a [[period (physics)|period]] of about 30 to 40 minutes. Locally, seiches have caused floods, destroyed port facilities and damaged the fishery: hence the local word for seiche, {{Nihongo|あびき|abiki}}, from {{Nihongo|網引き|amibiki}}, meaning 'the dragging-away of a fishing net'.

On occasion, [[tsunami]]s can produce seiches as a result of local geographic peculiarities. For instance, the tsunami that hit [[Hawaii]] in 1946 had a fifteen-minute interval between wave fronts. The natural resonant period of [[Hilo|Hilo Bay]] is about thirty minutes. That meant that every second wave was in phase with the bay, creating a seiche. As a result, Hilo suffered worse damage than any other place in Hawaii, with the combined tsunami and seiche reaching a height of {{convert|26|ft|m}} along the Bayfront, killing 96 people in the city alone. Seiche waves may continue for several days after a tsunami.

Tide-generated internal solitary waves ([[soliton]]s) can excite coastal seiches at the following locations: [[Magueyes Island]] in Puerto Rico,<ref>
{{cite journal
| doi = 10.1029/GL009i012p01305
| last = Giese
| first = Graham S.
|author2=R. B. Hollander |author3=J. E. Fancher |author4=B. S. Giese
 | title = Evidence of coastal Seiche excitation by tide-generated internal solitary waves.
| journal = Geophysical Research Letters
| volume = 9
| issue = 12
| pages = 1305–1308
| year = 1982
|bibcode = 1982GeoRL...9.1305G }}
</ref><ref>
{{cite journal
| doi = 10.1175/1520-0485(1990)020<1449:COLACS>2.0.CO;2
| last = Giese
| first = Graham S.
|author2=David C. Chapman |author3=Peter G. Black |author4=John A. Fornshell
 | title = Causation of Large-Amplitude Coastal Seiches on the Caribbean Coast of Puerto Rico
| journal = J. Phys. Oceanogr.
| volume = 20
| issue = 9
| pages = 1449–1458
| date = 1990
| bibcode = 1990JPO....20.1449G| doi-access = free
}}
</ref><ref>{{cite web |last=Alfonso-Sosa |first=Edwin |title=Estimated Speed of Aves Ridge Solitons Packets by Analysis of Sequential Images from the Moderate Resolution Imaging Spectroradiometer(MODIS) |pages=1–11 |date=September 2012 |doi=10.13140/RG.2.2.14561.45929 |doi-access=free |url=https://www.academia.edu/4950973 |access-date=2022-07-30 |archive-date=2022-07-30 |archive-url=https://web.archive.org/web/20220730162534/https://www.academia.edu/4950973/Estimated_Speed_of_Aves_Ridge_Solitons_Packets_by_Analysis_of_Sequential_Images_from_the_Moderate_Resolution_Imaging_Spectroradiometer_MODIS_S |url-status=live }}</ref>
[[Puerto Princesa]] in Palawan Island,<ref>
{{cite journal
| doi = 10.1175/1520-0485(1998)028<2418:TCBHSA>2.0.CO;2
| last = Giese
| first = Graham S.
|author2=David C. Chapman |author3=Margaret Goud Collins |author4=Rolu Encarnacion |author5=Gil Jacinto
 | title = The Coupling between Harbor Seiches at Palawan Island and Sulu Sea Internal Solitons
| journal = J. Phys. Oceanogr.
| volume = 28
| issue = 12
| pages = 2418–2426
| date = 1998
|bibcode=1998JPO....28.2418G| s2cid = 55974279
| doi-access = free
}}
</ref>
[[Trincomalee Bay]] in Sri Lanka,<ref>
{{cite journal
| doi = 10.1029/2009JC005673
| last = Wijeratne
| first = E. M. S.
|author2=P. L. Woodworth |author3=D. T. Pugh
 | title = Meteorological and internal wave forcing of seiches along the Sri Lanka coast
| journal = Journal of Geophysical Research: Oceans
| volume = 115
| issue = C3
| pages = C03014
| date = 2010
|bibcode = 2010JGRC..115.3014W | doi-access = free
}}
</ref><ref>{{cite web |last=Alfonso-Sosa |first=Edwin |title=Tide-Generated Internal Solitons in Bay of Bengal Excite Coastal Seiches in Trincomalee Bay |pages=1–16 |date=April 2014 |url=https://www.academia.edu/6707154 |doi=10.13140/RG.2.2.32105.70242 |doi-access=free |access-date=2022-07-30 |archive-date=2022-07-30 |archive-url=https://web.archive.org/web/20220730162534/https://www.academia.edu/6707154/Tide-Generated_Internal_Solitons_in_Bay_of_Bengal_Excite_Coastal_Seiches_in_Trincomalee_Bay |url-status=live }}</ref>
and in the [[Bay of Fundy]] in eastern Canada, where seiches cause some of the highest recorded tidal fluctuations in the world.<ref>{{cite web|url=http://www.pc.gc.ca/eng/pn-np/nb/fundy/visit/marees-tides.aspx|title=The Bay of Fundy's Giant Tides|date=2017-03-28|website=Parks Canada – Fundy National Park|access-date=9 April 2018|archive-date=2016-03-04|archive-url=https://web.archive.org/web/20160304050045/http://www.pc.gc.ca/eng/pn-np/nb/fundy/visit/marees-tides.aspx|url-status=dead }}</ref>
A dynamical mechanism exists for the generation of coastal seiches by deep-sea internal waves. These waves can generate a sufficient current at the shelf break to excite coastal seiches.<ref>
{{cite journal
| doi = 10.1175/1520-0485(1990)020<1459:AMFTGO>2.0.CO;2
| last = Chapman
| first = David C.
|author2=Graham S. Giese
 | title = A Model for the Generation of Coastal Seiches by Deep-Sea Internal Waves
| journal = J. Phys. Oceanogr.
| volume = 20
| issue = 9
| pages = 1459–1467
| date = 1990
| bibcode = 1990JPO....20.1459C
| doi-access = free
}}
</ref>

In September 2023, an enormous landslide resulting from a melting glacier near [[Dickson Fjord]] in Greenland triggered a [[megatsunami]] about {{convert|200|m|ft}} high.<ref name="ArsTechnica2024">{{cite web | last1=Hicks | first1=Steven | last2=Svennevig | first2=Kristian | date=2024-09-14 | title=Bizarre, nine-day seismic signal caused by epic landslide in Greenland | website=Ars Technica | url=https://arstechnica.com/science/2024/09/bizarre-nine-day-seismic-signal-caused-by-epic-landslide-in-greenland/ | access-date=2024-09-15}}</ref><ref>{{cite journal |last1=Carrillo-Ponce |first1=Angela |last2=Heimann |first2=Sebastian |last3=Petersen |first3=Gesa M. |last4=Walter |first4=Thomas R. |last5=Cesca |first5=Simone |last6=Dahm |first6=Torsten |date=2024 |title=The 16 September 2023 Greenland Megatsunami: Analysis and Modeling of the Source and a Week-Long, Monochromatic Seismic Signal |journal=The Seismic Record |volume=4 |issue=3 |pages=172–183 |doi=10.1785/0320240013 |doi-access=free|bibcode=2024SeisR...4..172C }}</ref><ref>{{cite journal |last1=Svennevig |first1=Kristian |last2=Hicks |first2=Stephen P. |last3=Forbriger |first3=Thomas |last4=Lecocq |first4=Thomas |last5=Widmer-Schnidrig |first5=Rudolf |last6=Mangeney |first6=Anne |last7=Hibert |first7=Clément |last8=Korsgaard |first8=Niels J. |last9=Lucas |first9=Antoine |last10=Satriano |first10=Claudio |last11=Anthony |first11=Robert E. |last12=Mordret |first12=Aurélien |last13=Schippkus |first13=Sven |last14=Rysgaard |first14=Søren |last15=Boone |first15=Wieter |date=13 September 2024 |title=A rockslide-generated tsunami in a Greenland fjord rang Earth for 9 days |journal=Science |volume=385 |issue=6714 |pages=1196–1205 |doi=10.1126/science.adm9247 |last16=Gibbons |first16=Steven J. |last17=Cook |first17=Kristen L. |last18=Glimsdal |first18=Sylfest |last19=Løvholt |first19=Finn |last20=Van Noten |first20=Koen |last21=Assink |first21=Jelle D. |last22=Marboeuf |first22=Alexis |last23=Lomax |first23=Anthony |last24=Vanneste |first24=Kris |last25=Taira |first25=Taka'aki |last26=Spagnolo |first26=Matteo |last27=De Plaen |first27=Raphael |last28=Koelemeijer |first28=Paula |last29=Ebeling |first29=Carl |last30=Cannata |first30=Andrea |last31=Harcourt |first31=William D. |last32=Cornwell |first32=David G. |last33=Caudron |first33=Corentin |last34=Poli |first34=Piero |last35=Bernard |first35=Pascal |last36=Larose |first36=Eric |last37=Stutzmann |first37=Eleonore |last38=Voss |first38=Peter H. |last39=Lund |first39=Bjorn |last40=Cannavo |first40=Flavio |last41=Castro-Díaz |first41=Manuel J. |last42=Chaves |first42=Esteban |last43=Dahl-Jensen |first43=Trine |last44=Pinho Dias |first44=Nicolas De |last45=Déprez |first45=Aline |last46=Develter |first46=Roeland |last47=Dreger |first47=Douglas |last48=Evers |first48=Läslo G. |last49=Fernández-Nieto |first49=Enrique D. |last50=Ferreira |first50=Ana M. G. |last51=Funning |first51=Gareth |last52=Gabriel |first52=Alice-Agnes |last53=Hendrickx |first53=Marc |last54=Kafka |first54=Alan L. |last55=Keiding |first55=Marie |last56=Kerby |first56=Jeffrey |last57=Khan |first57=Shfaqat A. |last58=Dideriksen |first58=Andreas Kjær |last59=Lamb |first59=Oliver D. |last60=Larsen |first60=Tine B. |last61=Lipovsky |first61=Bradley |last62=Magdalena |first62=Ikha |last63=Malet |first63=Jean-Philippe |last64=Myrup |first64=Mikkel |last65=Rivera |first65=Luis |last66=Ruiz-Castillo |first66=Eugenio |last67=Wetter |first67=Selina |last68=Wirtz |first68=Bastien|pmid=39264997 |bibcode=2024Sci...385.1196S |hdl=2164/24232 |hdl-access=free }}</ref> This was followed by a seiche with waves up to {{convert|7|m|ft}} high oscillating within the fjord.<ref name="NPR2024">{{cite web |last1=Chappell |first1=Bill |title=A landslide linked to climate change 'rang' the Earth for 9 days, researchers say |url=https://www.npr.org/2024/09/13/g-s1-22858/a-landslide-linked-to-climate-change-rang-the-earth-for-9-days-researchers-say |publisher=NPR |date=13 September 2024}}</ref> This seiche lasted nine days, reflecting the avalanche's large size and the fjord's long, narrow shape. During that period, it generated unusual seismic reverberations detected around the world, puzzling seismologists for some time before they could identify their source.<ref name="ArsTechnica2024" /><ref name="NPR2024" /><ref name="WashingtonPost2024">{{Cite news |last=Patel |first=Kasha |date=2024-09-14 |title=A rumble echoed around the world for nine days. Here's what caused it. |url=https://www.washingtonpost.com/climate-environment/2024/09/12/seismic-signal-climate-change-landslide-greenland/ |access-date=2024-09-15 |newspaper=The Washington Post|language=en-US}}</ref>

[[File:Illustration of the phenomenon of seiches.png|thumb|350px|Illustration of the initiation of surface and subsurface thermocline seiches.]]

===Underwater (internal) waves===
Seiches are also observed beneath the surface of constrained bodies of water, acting along the [[thermocline]].<ref>The [[thermocline]] is the boundary between colder lower layer ([[hypolimnion]]) and warmer upper layer ([[epilimnion]]).</ref>

In analogy with the [https://encyclopedia2.thefreedictionary.com/Merian%27s+formula Merian formula], the expected period of the internal wave can be expressed as:<ref>Mortimer, C. H. (1974). Lake hydrodynamics. Mitt. Internat. Verein. Limnol. 20, 124–197.</ref>

: <math>T = \frac{2L}{c}</math>       with       <math>c^2 = g \frac{\rho_2-\rho_1}{\rho_2} \frac{h_1 h_2}{h_1+h_2}</math>

where ''T'' is the natural [[Frequencies|period]], ''L'' is the length of the water body, <math>h_1, h_2</math> the average thicknesses of the two layers separated by [[stratification (water)|stratification]] (e.g. [[epilimnion]] and [[hypolimnion]]), <math>\rho_1, \rho_2</math> the [[densities]] of these two same layers and ''g'' the [[Earth's gravity|acceleration of gravity]].

As the [[thermocline]] moves up and down a sloping lake bed, it creates a 'swash zone', where temperatures can vary rapidly,<ref>{{Cite journal|last1=Cossu|first1=R.|last2=Ridgway|first2=M.S.|last3=Li|first3=J.Z.|last4=Chowdhury|first4=M.R.|last5=Wells|first5=M.G.|date=2017|title=Wash-zone dynamics of the thermocline in Lake Simcoe, Ontario|journal=Journal of Great Lakes Research|volume=43|issue=4|pages=689–699|doi=10.1016/j.jglr.2017.05.002|bibcode=2017JGLR...43..689C |issn=0380-1330|doi-access=free}}</ref> potentially affecting fish habitat. As the thermocline rises up a sloping lake bed, it can also cause [[benthic]] turbulence by convective overturning, whereas the falling thermocline experiences greater stratification and low turbulence at the lake bed.<ref>{{Cite journal|last1=Cossu|first1=Remo|last2=Wells|first2=Mathew G.|date=2013-03-05|title=The Interaction of Large Amplitude Internal Seiches with a Shallow Sloping Lakebed: Observations of Benthic Turbulence in Lake Simcoe, Ontario, Canada|journal=PLOS ONE|volume=8|issue=3|pages=e57444|doi=10.1371/journal.pone.0057444|pmid=23472085|pmc=3589419|bibcode=2013PLoSO...857444C|issn=1932-6203|doi-access=free}}</ref><ref>{{Cite journal|last1=Bouffard|first1=Damien|last2=Wüest|first2=Alfred|date=2019-01-05|title=Convection in Lakes|journal=Annual Review of Fluid Mechanics|volume=51|issue=1|pages=189–215|doi=10.1146/annurev-fluid-010518-040506|bibcode=2019AnRFM..51..189B|s2cid=125132769|issn=0066-4189|url=http://infoscience.epfl.ch/record/264776/files/Convection%20in%20lakes.pdf}}</ref> Internal waves can also degenerate into non-linear internal waves on sloping lake-beds.<ref>{{Cite journal|last1=Boegman|first1=L.|last2=Ivey|first2=G. N.|last3=Imberger|first3=J.|date=September 2005|title=The degeneration of internal waves in lakes with sloping topography|journal=Limnology and Oceanography|volume=50|issue=5|pages=1620–1637|doi=10.4319/lo.2005.50.5.1620|bibcode=2005LimOc..50.1620B|s2cid=55292327|issn=0024-3590|url=https://api.research-repository.uwa.edu.au/files/3235728/Boegman_Leon_2004.pdf|access-date=2020-09-06|archive-date=2019-04-29|archive-url=https://web.archive.org/web/20190429003848/https://api.research-repository.uwa.edu.au/files/3235728/Boegman_Leon_2004.pdf|url-status=live}}</ref> When such non-linear waves break on the lake bed, they can be an important source of turbulence and have the potential for sediment resuspension<ref>{{Cite journal|last1=Boegman|first1=Leon|last2=Stastna|first2=Marek|date=2019-01-05|title=Sediment Resuspension and Transport by Internal Solitary Waves|journal=Annual Review of Fluid Mechanics|volume=51|issue=1|pages=129–154|doi=10.1146/annurev-fluid-122316-045049|bibcode=2019AnRFM..51..129B|s2cid=126363796|issn=0066-4189|doi-access=free}}</ref>

===Cave seiches===
On September 19, 2022, a seiche reaching {{Convert|4|ft|m|abbr=off}} occurred at [[Devils Hole]] at [[Death Valley National Park]] in the U.S. after a [[2022 Western Mexico earthquake|7.6-magnitude earthquake]] hit western [[Mexico]], about {{Convert|1500|mi|km|abbr=off}} away. Seiches were also observed in the cave after powerful earthquakes in 2012, 2018 and 2019.<ref name="BNO">{{Cite web |date=September 21, 2022 |title=Mexico earthquake caused waves at California's Death Valley |url=https://bnonews.com/index.php/2022/09/mexico-earthquake-caused-waves-at-californias-death-valley/ |access-date=September 22, 2022 |website=[[BNO News]]}}</ref>