Science1 distinct publisher3 min readPublished
The warm water off Southern and Central California came from a marine heat wave that predates the El Niño NOAA declared in June, which leaves coastal sea level and upwelling, rather than warm-water fish, as the indicators that still discriminate.
The Scientist · Science desk
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The two warmings arrive by different roads, and that is what makes them separable at all. Weakened equatorial winds, periodically reversing into westerly bursts, launch oceanic Kelvin waves eastward along the equator; on reaching Central and South America the energy turns north as coastal trapped waves, the pathway NOAA describes as an oceanic teleconnection [7]. The waves travel underwater, but they raise coastal sea level by roughly 15 cm, which is enough to register on tide gauges and on satellites [8]. Fifteen centimetres is a small signal with one large virtue: its origin can be traced back to the equator, and a warm sea surface off Long Beach cannot be.
Downstream of the waves the thermocline deepens [11], and by a separate route the tropics reshape atmospheric pressure over the North Pacific in a way that can weaken or reverse the winds that normally drive cold, nutrient-rich upwelling [12]. Michael Jacox of NOAA's Southwest Fisheries Science Center says the oceanic route matters most off Southern California and the atmospheric route most off the Pacific Northwest [13]. Two routes with different arrival characteristics along one 4,000-kilometre coast means a single coastwide trigger date is the wrong object to be waiting for, even though both routes end in surface warming in a nearshore band running from Baja California to Alaska [14].
The biological indicators have degraded faster than the physical ones. Dorado, yellowfin tuna and striped marlin used to be the visible tell of an El Niño; they have already pushed north during marine heat waves with no El Niño present, which is why NOAA no longer treats them as diagnostic [15]. The striped marlin landed off Washington in August set a state record [16], and it tells you the water is warm without telling you why.
The historical analogue carries a similar caution. NOAA Fisheries and Scripps documented 36 unusual species off California across the 2014 to 2018 warm period, most of them warm-water associates, blue marlin and giant manta ray among them [19], and 14 of those were first records for the California Current [20]. That is 39 percent of the tally arriving with no prior observation [21], which is a striking number and also an uncontrolled one: the account reports the count for the warm years and no equivalent count for the years before The Blob, so the figure describes what was seen during a warm anomaly rather than the rate at which such sightings occur otherwise. The sequence itself is the part worth holding onto, because 2014 to 2018 opened with a heat wave and closed with an El Niño [18].
For the rest of this year, then, a warm anomaly off California is consistent with either story, and the measurements that distinguish them are coastal sea level and the state of the upwelling winds. Nate Mantua's expectation that the larger coastal effects land in fall and winter [10] is the schedule to plan against, not June's declaration.
Ranked by verification strength, evidence, and original report placement.
The unusual warmth in the ocean off Southern and Central California is from a recent marine heat wave that predates the current El Nino.
Much of the Pacific Coast is experiencing relatively normal conditions while still awaiting the impacts of what could be a very strong El Nino.
In June, NOAA's National Weather Service declared that El Nino had developed, a finding based on ocean temperatures from the tropical Pacific Ocean near the equator, which warm ahead of El Nino's impact on the Americas.
Eastern tropical Pacific temperatures have already risen more than 2 degrees C (about 3.6 degrees F) above normal.
El Nino-related warming along the West Coast typically lags the eastern tropical Pacific temperature increase by a few months.
NOAA Fisheries scientists are tracking West Coast conditions as part of the agency's Integrated Ecosystem Assessment.
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Specific mechanism, no data shown
The physics is stated precisely enough to be checkable by someone else: a coastal sea level bump of about 15 cm that tide gauges and satellites can resolve, thermocline deepening behind it, upwelling winds weakening under a shifted North Pacific pressure pattern, and a May-June arrival for the first waves. Two NOAA scientists are named for the interpretive calls, and the 2014-2018 species counts were compiled with Scripps. What is missing is any of the measurements themselves, and the account comes from the agency that owns the instruments.
Nothing to count yet
This reporting measures ocean state, not behaviour. The one thing anyone is shown doing, squid boats working north along Oregon and Washington, is offered as a symptom of warm water rather than as a response to NOAA's indicators, and no port, fishery or agency decision is recorded anywhere in it.
Undersold on purpose
A state-record marlin off Washington and unusually warm water off Southern California would carry an El Niño headline without effort, and NOAA spends the piece taking that headline apart, going as far as retiring its own most quotable indicator by saying warm-water fish no longer tell you anything about El Niño. The reading sits modestly below zero because the coastal warming the agency does expect for fall and winter, in a band from Baja California to Alaska, gets less room than the caveats around it.
The monitor describes why monitoring is needed
NOAA wrote this about NOAA's instruments, and phys.org left the first person in place. Its practical upshot is that the free public indicators, warm fish in the wrong place and crabs on the beach, have stopped working, leaving the agency's tide gauges, sampling lines and ecosystem assessment as the way to know anything. That is a defensible scientific position and also an argument for the programme's budget. No commercial stake appears, and no outside voice tests the framing.
One carrier, one voice
Two named scientists and a coherent physical argument keep this from scoring low; a single publisher relaying a single agency, with no second reading of the tropical anomaly or the coastal timing, keeps it from scoring high. The republication also breaks off mid-sentence in the species-richness section, so part of the indicator set NOAA promised to walk through never arrives.