{"id":5492,"date":"2023-12-11T12:03:37","date_gmt":"2023-12-11T19:03:37","guid":{"rendered":"https:\/\/blogs.oregonstate.edu\/gemmlab\/?p=5492"},"modified":"2023-12-11T12:03:37","modified_gmt":"2023-12-11T19:03:37","slug":"el-nino-de-navidad-what-is-atmospheric-santa-claus-bringing-to-oregon-krill-and-whales","status":"publish","type":"post","link":"https:\/\/blogs.oregonstate.edu\/gemmlab\/2023\/12\/11\/el-nino-de-navidad-what-is-atmospheric-santa-claus-bringing-to-oregon-krill-and-whales\/","title":{"rendered":"El Ni\u00f1o de Navidad: What is atmospheric Santa Claus bringing to Oregon krill and whales?"},"content":{"rendered":"\n

By <\/em>Rachel Kaplan<\/em><\/a>, PhD student, Oregon State University College of Earth, Ocean, and Atmospheric Sciences and Department of Fisheries, Wildlife, and Conservation Sciences, <\/em>Geospatial Ecology of Marine Megafauna Lab<\/em><\/a><\/em><\/p>\n\n\n\n

Early June marked the onset of El Ni\u00f1o conditions in the Pacific Ocean\u00a0, which have been strengthening through the fall and winter. For Oregonians, this climate event means unseasonably warm December days, less snow and overall precipitation (it\u2019s sunny as I write this!), and the potential for increased wildfires and marine heatwaves next summer.<\/p>\n\n\n\n

This phenomenon occurs about every two to seven years as part of the El Ni\u00f1o Southern Oscillation (ENSO), a cyclical rotation of atmospheric and oceanic conditions in the Pacific Ocean that is initiated by departures from and returns to \u201cnormal conditions\u201d at the equator. Typically, the trade winds blow warm water west along the equator, and El Ni\u00f1o occurs when these winds weaken or reverse. As a result, the upwelling of cold water at the equator ceases, and warm water flows towards the west coast of the Americas, rather than its typical pathway towards Asia. When the trade winds resume their normal direction, usually after months or a year, the system returns to \u201cnormal\u201d conditions \u2013 or, it can enter the cool La Ni\u00f1a part of the cycle, in which the trade winds are stronger than normal. \u201cEl Ni\u00f1o de Navidad\u201d was named by South American fisherman in the 1600s because this event tends to peak in December \u2013 and El Ni\u00f1o is clearly going to be a guest for Christmas this year.<\/p>\n\n\n

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Figure 1.<\/em> Maps of sea surface temperature anomalies show Pacific Ocean conditions during a strong La Ni\u00f1a (top) and El Ni\u00f1o (bottom). Source: NOAA climate.gov<\/a><\/figcaption><\/figure>\n<\/div>\n\n\n

These events at the equator trigger changes in global atmospheric circulation patterns, and they can shape weather around the world. Teleconnection, the coherence between meteorological and environmental phenomena occurring far apart, is to me one of the most incredible things about the natural world.\u00a0 This coherence means that the biological community off the Oregon coast is strongly impacted by events initiated at the equator, with consequences that we don\u2019t yet fully understand.<\/p>\n\n\n\n

The effects of El Ni\u00f1o are diverse \u2013 floods in some places, droughts in others \u2013 and their onset can mean wildly different things for Oregon, Peru, Alaska, and beyond. As we tap our fingers waiting to be able to ski and snowboard in Oregon, what does our current El Ni\u00f1o event mean for the life in the waters off our coast?<\/p>\n\n\n\n

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Figure 2. <\/em>Anomalous conditions at the equator qualified as an El Ni\u00f1o event in June 2023.<\/figcaption><\/figure>\n\n\n\n

ENSO plays a big role in the variability in our local Northern California Current (NCC) system, and the outcomes of these events can differ based on the strength and how the signal propagates through the ocean and atmosphere (Checkley & Barth, 2009). Large-scale \u201ccoastal-trapped\u201d waves flowing alongshore can bring the warm water signal of an El Ni\u00f1o to our ocean backyard in a matter of weeks. One of the first impacts is a deepening of the thermocline, the upper ocean\u2019s steep gradient in temperature, which changes the cycling of important nutrients in the surface ocean. This can result in a decrease in upwelling and primary productivity that sends ramifications through the food web, including consequences for grazers and predators like zooplankton, marine mammals, and seabirds (Checkley & Barth, 2009).<\/p>\n\n\n\n

In addition to these ecosystem effects that result from local changes, the ocean community can also receive new visitors from afar, and see others flee\u00a0. For krill, the shrimp-like whale prey that I spend a lot of my time thinking about, community composition can change as subtropical species typically found off southern and Baja California\u00a0are displaced by horizontal ocean flow, or as resident species head north (Lilly & Ohman, 2021).<\/p>\n\n\n

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Figure 3<\/em>. This Euphausia gibboides<\/em> krill is typically found in offshore subtropical habitats but moves north and inshore during El Ni\u00f1o events, and tends to persist awhile in these new environments, impacting the local zooplankton community. Source: Solvn Zankl<\/a><\/figcaption><\/figure>\n<\/div>\n\n\n

The two main krill species that occur in the NCC, Euphausia pacifica and Thysanoessa spinifera<\/em>, favor the cool, coastal waters typical off the coast of Oregon. During El Ni\u00f1o events, E. pacifica <\/em>tends to contract its distribution inshore in order to continue occupying these conditions, increasing its spatial overlap with T. spinifera <\/em>(Lilly & Ohman, 2021). In addition, both tend to shift their populations north, toward cooler, upwelling waters (Lilly & Ohman, 2021).<\/p>\n\n\n\n

These krill species are a favored prey of rorqual whales, and the coast of Oregon is an important foraging ground for humpback, blue, and fin whales. Predators tend to follow their prey, and shifting distributions of these krill species may cause whales to move, too. During the 2014-2015 \u201cBlob\u201d event in the Pacific Ocean, a marine heatwave was exacerbated by El Ni\u00f1o conditions. Humpback whales in central California shifted their distributions inshore in response to sparse offshore krill, increasing their overlap with fishing gear and leading to an increase in entanglement events (Santora et al., 2020). Further north, these conditions even led humpback whales to forage in the Columbia River!<\/p>\n\n\n\n

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