{"id":8927,"date":"2026-03-18T13:55:28","date_gmt":"2026-03-18T12:55:28","guid":{"rendered":"https:\/\/nersc.no\/?p=8927"},"modified":"2026-03-18T13:56:02","modified_gmt":"2026-03-18T12:56:02","slug":"sound-sent-across-long-distances-can-reveal-ocean-temperatures-beneath-sea-ice","status":"publish","type":"post","link":"https:\/\/nersc.no\/en\/features\/sound-sent-across-long-distances-can-reveal-ocean-temperatures-beneath-sea-ice\/","title":{"rendered":"Sound sent across long distances can reveal ocean temperatures beneath sea ice"},"content":{"rendered":"

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<\/div>[\/vc_column][\/vc_row][vc_row][vc_column width=”2\/3″ css=”.vc_custom_1693479579188{background-color: #ffffff !important;}”]

Sound sent across long distances can reveal ocean temperatures beneath sea ice<\/h1><\/div>[vc_column_text css=””]Researchers at the Nansen Center have sent sound signals across the Arctic Ocean, over distances comparable to traveling from Bergen to Lisbon by plane. The experiment shows that acoustic measurements can provide precise, year<\/strong>\u2011round observations of temperature variations under the sea ice.<\/strong><\/p>\n

To understand and document the rapid changes in the Arctic, good and continuous observations are essential. But large parts of the ocean are hidden under ice most of the year. That makes it very difficult to measure changes in temperature and ocean currents. Traditionally, scientists rely on point measurements using instruments that are either anchored to the seafloor or drifting freely in the water. Satellites give good observations of the surface, but under sea ice we need other methods.<\/p>\n

Acoustic thermometry as aid
\n<\/b>In the CAATEX<\/span><\/a> experiment, the researchers used an \u201cacoustic thermometer.\u201d By sending sound signals through the water, they measured how fast the sound traveled \u2013 a speed that changes with the temperature of the ocean. Acoustic thermometers give precise measurements of ocean temperatures over very long distances. These large\u2011scale measurements complement traditional point measurements extremely well.<\/p>\n

Sound waves can be detected 2,600 kilometers from the source
\n<\/strong>From 2019 to 2020, six bottom\u2011anchored moorings were placed in the Arctic Ocean; three north of Svalbard and three north of Alaska. Each mooring was roughly 4,000 meters long from seafloor to surface and carried 40 instruments measuring different ocean conditions at different depths. What made the CAATEX experiment unique was that two of the moorings had their own sound sources. Every third day, these sent out signals at around 35 Hz, which were picked up by the instruments on the other moorings. The signals could be detected more than 2,600 kilometers away from a sound source north of Svalbard.<\/p>\n

Large variations through the year
\n<\/strong>The measurements taken across 2,600 kilometers take around half an hour of travel time. In that time, the ocean changes very little, which means the data gives an almost instantaneous snapshot of ocean temperature. At the same time, the measurements show that sound speed in the ocean under sea ice varies significantly throughout the year. These variations reveal changes in the ocean that no other observations capture.<\/p>\n

A first step, temperature calculations come next
\n<\/strong>A recently published study focuses on how fast sound travels through the Arctic Ocean. The next step is to use these measurements to calculate the average sound speed at different depths across the Arctic. That will also allow researchers to estimate ocean temperature.<\/p>\n

A method for the future
\n<\/strong>Using sound to measure temperature gives researchers something they have long lacked in the Arctic: stable and precise temperature measurements across large ocean areas, all year round. Once the temperature data is ready, it will give important insights into how the entire Arctic Ocean changes through the seasons and from year to year. Such large\u2011scale measurements are important for climate research, both to monitor climate change and to validate and improve model systems. To capture the slow changes in climate, the measurements must be repeated. It is now five years since CAATEX, and researchers at the Nansen Center are working with international partners to secure funding to repeat the measurements.<\/p>\n

Key researchers:<\/strong> Hanne Sagen<\/span><\/a>, Espen Storheim<\/span><\/a>, Stein Sandven<\/a><\/span>[\/vc_column_text][\/vc_column][vc_column width=”1\/3″ css=”.vc_custom_1695033709348{padding-right: 0px !important;}”]

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CAATEX in a nutshell<\/strong><\/h3>\n

CAATEX<\/a> stands for \u201cCoordinated Arctic Acoustic Thermometry Experiment\u201d. The project ran from 2018 to 2022. The Nansen Center led the work, with both Norwegian and American partners involved. In CAATEX, researchers used acoustic thermometry to measure ocean temperature beneath Arctic sea ice over long distances and long time periods.<\/p><\/div>

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What is an acoustic thermometer?<\/strong><\/h3>\n

An acoustic thermometer uses sound to measure temperature in the ocean. The principle is simple: sound travels faster in warm water than in cold water. In the Arctic, a typical sound speed is around 1465 meters per second, while in temperate oceans it is closer to 1500 meters per second. A temperature change of just one degree Celsius can increase sound speed by 4 to 4.5 meters per second.<\/p>\n

Researchers send sound signals from a sound source and measure how long it takes for the signal to reach a listening station. The travel time reveals how fast the sound has moved, which in turn tells us something about the temperature of the water it passed through. This allows scientists to track temperature changes over large distances and long periods.<\/p>\n

Read more here<\/a>.<\/p><\/div>

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Publication<\/strong><\/h3>\n

\u00abTransarctic acoustic transmissions during the coordinated Arctic acoustic thermometry experiment in 2019\u20132020\u00bb, in\u00a0The Journal of the Acoustical Society of America <\/em><\/p>\n

Read the publication here<\/span><\/a>.<\/p><\/div>[\/vc_column][\/vc_row]<\/p>\n<\/div>","protected":false},"excerpt":{"rendered":"

[vc_row][vc_column][\/vc_column][\/vc_row][vc_row][vc_column width=”2\/3″ css=”.vc_custom_1693479579188{background-color: #ffffff !important;}”][vc_column_text css=””]Researchers at the Nansen Center have sent sound signals across the Arctic Ocean, over distances comparable to traveling from Bergen to Lisbon by plane. The experiment shows that acoustic measurements can provide precise, year\u2011round observations of temperature variations under the sea ice. To understand and document the rapid changes in […]<\/p>\n","protected":false},"author":4,"featured_media":8929,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_relevanssi_hide_post":"","_relevanssi_hide_content":"","_relevanssi_pin_for_all":"","_relevanssi_pin_keywords":"","_relevanssi_unpin_keywords":"","_relevanssi_related_keywords":"","_relevanssi_related_include_ids":"","_relevanssi_related_exclude_ids":"","_relevanssi_related_no_append":"","_relevanssi_related_not_related":"","_relevanssi_related_posts":"","_relevanssi_noindex_reason":"","footnotes":""},"categories":[80],"tags":[],"class_list":["post-8927","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-features"],"acf":[],"publishpress_future_action":{"enabled":false,"date":"2026-05-07 18:19:05","action":"change-status","newStatus":"draft","terms":[],"taxonomy":"category","extraData":[]},"publishpress_future_workflow_manual_trigger":{"enabledWorkflows":[]},"_links":{"self":[{"href":"https:\/\/nersc.no\/en\/wp-json\/wp\/v2\/posts\/8927","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/nersc.no\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/nersc.no\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/nersc.no\/en\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/nersc.no\/en\/wp-json\/wp\/v2\/comments?post=8927"}],"version-history":[{"count":2,"href":"https:\/\/nersc.no\/en\/wp-json\/wp\/v2\/posts\/8927\/revisions"}],"predecessor-version":[{"id":8932,"href":"https:\/\/nersc.no\/en\/wp-json\/wp\/v2\/posts\/8927\/revisions\/8932"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/nersc.no\/en\/wp-json\/wp\/v2\/media\/8929"}],"wp:attachment":[{"href":"https:\/\/nersc.no\/en\/wp-json\/wp\/v2\/media?parent=8927"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/nersc.no\/en\/wp-json\/wp\/v2\/categories?post=8927"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/nersc.no\/en\/wp-json\/wp\/v2\/tags?post=8927"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}