Scientists are pretty good at recognizing marine heat waves: A global network of thousands of oceanic buoys and orbiting satellites allow them to see, in real time, ocean surface temperatures, changing currents and storm systems as they develop, move or stall from the Antarctic to the North Pole.
What’s harder to see is what’s happening to the marine ecosystems below — to the fish, invertebrates, plants and mammals.
“There’s sort of a disconnect between temperature and how something like temperature impacts species distribution patterns or how fisheries are operating or how protected species might be responding,” said Jarrod Santora, a fisheries biologist with the National Oceanic and Atmospheric Administration. “There’s a big jump between what we identify as a temperature anomaly and process in the ocean.”
Some animals may move down the water column to darker, colder waters. Others may move north — or south — depending upon where the cooler waters are. Many may flourish; others will perish.
And some may not be affected at all, said Santora.
“We’re just looking at temperature anomalies that focus on the skin of the ocean; we don’t know what’s happening inside,” he said.
That’s why Heather Welch, a marine spatial ecologist at UC Santa Cruz, and other researchers have created statistical models designed to predict where animals will go when things heat up.
“So one of the tricky things with heat wave impacts is you have to be lucky and actually have direct observations during the events,” she said. Such direct observations are often made via GPS tags on animals, or observations made from a research vessel that happens to be in the right place at the right time.
But with a model, you can use data collected not just during a heat wave, but at other times, too, and “extrapolate to see what would have happened during heat waves, or what did happen,” she said.
Earlier this month, she and a team of researchers published the results of a model that they used to predict the movements of 14 marine predators — a selection of mammals, birds and fish — in the North Pacific during the heatwaves of 2014, 2015, 2019 and 2020.
What they found was a “wide diversity of responses across heat waves,” she said. For instance, during the heat waves of 2014 and 2015, bluefin and albacore tuna moved northwest. In 2019 and 2020 they moved southeast.
The researchers also found that different species responded … well, differently.
“So if you look at a blue whale versus an albatross, they’re going to do different things,” she said, noting that such an observation hadn’t really been seen before — because most studies of marine heat waves focused on one animal in one heat wave.
It’s a point that Alexa Fredstone, an assistant professor of ocean sciences at UC Santa Cruz, echoed.
“We have a number of stories that individually make sense about how particular communities were affected,” she said. “But every story is unique and the most common thing that we see actually is when there has been a marine heat wave, we don’t really see any coherent response in the ecosystem.”
She said heat waves have had clearly detrimental impacts on shallow water ecosystems, such as kelp forests and coral reefs. But once you get farther down the water column, things get a little murkier.
She and a team of ocean and data scientists from across North America and Europe looked at the effects of marine heat waves on fish between 1993 and 2019. They found no clear effect — nothing beyond what you’d expect with natural variability.
“What’s surprising about this is that studies have shown that, over decades, fish are shifting towards the poles on average” as ocean temperatures climb from global warming, she said. “So we know that there’s a long-term climate signal. Maybe that’s just easier to detect statistically than the short term effect of a heat wave?”
For fish like salmon, which require both marine and freshwater environments, the situation is slightly different — and the combination of heat waves in the North Pacific on top of a warming planet, is a boon to some species, and a disaster to others, said Nate Mantua, a fish biologist with NOAA.
He said warmer temperatures in places like the Gulf of Alaska or along the Pacific Coast, cut “off the food supply right at the base … leading into a longer food chain and just kind of less nutritious food,” for salmon.
But if “you get far enough north,” warming may actually be benefiting salmon like the Bering Sea and Bristol Bay sockeye salmon, he said. In the last 10 years, these fish had “the biggest run … the biggest harvest ever. Fifty-million fish harvested.”
He said that Russia’s Pacific salmon fishery this year also “has never been higher. It’s off the charts, but it’s almost entirely due to pink salmon from Russia and the stock populations in Bristol Bay. Everywhere else things are not good.”
Farther north than that? “That’s an interesting wrinkle,” Mantua said. “The salmon there have been doing extremely poorly the last 20 years.”
He said that was probably because of a combination of problems in the marine food web in the northern Bering Sea, as well as in their freshwater habitat.
“They have a really long migration through the interior of Alaska and it can get very warm there in the summer,” he said. “Twenty-four hours a day of light and a really big, broad, muddy river that soaks up a lot of sunshine.”
It’s for species such as this — the ones that need protecting — that Welch, who is also a researcher with NOAA, hopes her and others’ ecological forecasting models will help.
Fortunately, there are areas that appear more resilient to heat waves than others.
Ryan Walters, an oceanographer at Cal Poly San Luis Obispo, said areas with strong upwelling — like the cool strip along California’s coastline — appear to be less affected by heat waves than other areas in the ocean, potentially providing a cool haven for animals looking to avoid heat.
“It may be that these little pockets along the coastline, where we have this upwelling … may be a spot where marine animals can seek refuge from warmer waters elsewhere,” he said.
Wanasayansi wana uwezo wa kutambua mawimbi ya joto ya baharini: Mtandao wa maelfu ya buo za baharini na satelaiti zinazozunguka huwaruhusu kuona, kwa wakati halisi, joto la uso wa bahari, mabadiliko ya mkondo na mifumo ya dhoruba wakati zinaendelea, kusonga au kusimamishwa kutoka Antaktika hadi Ncha ya Kaskazini. Kile kinachokuwa vigumu kuona ni kile kinachotokea kwa mifumo ya ikolojia ya baharini chini - kwa samaki, wanyama wasio na uti wa mgongo, mimea na mamalia. "Kuna aina ya kutokuunganishwa kati ya joto na jinsi kitu kama joto huathiri mifumo ya usambazaji wa spishi au jinsi uvuvi unavyofanya kazi au jinsi spishi zilizohifadhiwa zinaweza kujibu, "alisema Jarrod Santora, mwanabiolojia wa uvuvi na Utawala wa Kitaifa wa Bahari na Anga." <unk>Kuna kuruka kubwa kati ya kile tunachokitambua kama anomaly ya joto na mchakato katika bahari.<unk> Baadhi ya wanyama wanaweza kuhamia chini ya safu ya maji kwa maji nyeusi, baridi. Nyingine zaweza kusonga kaskazini <unk> au kusini <unk> ikitegemea mahali ambapo maji baridi zaidi yapo. Wengi huenda wakafanikiwa; wengine watapotea. Na huenda wengine wasiathiriwa hata kidogo, akasema Santora. "Tunaangalia tu anomalies joto kwamba kuzingatia ngozi ya bahari; hatujui nini kinachotokea ndani, "alisema. Heather Welch, mtaalamu wa mazingira ya baharini katika Chuo Kikuu cha Santa Cruz, na watafiti wengine wameunda mifano ya takwimu iliyoundwa kutabiri wanyama wataenda wapi wakati joto litakapopanda. "Kwa hiyo moja ya mambo magumu na athari za wimbi la joto ni kwamba lazima uwe na bahati na kwa kweli uwe na uchunguzi wa moja kwa moja wakati wa matukio", alisema. Mara nyingi uchunguzi huo unafanywa kupitia vifaa vya GPS kwenye wanyama, au kutoka kwa chombo cha utafiti ambacho kinapatikana mahali panapofaa wakati unaofaa. Lakini kwa mfano, unaweza kutumia data zilizokusanywa sio tu wakati wa wimbi la joto, lakini wakati mwingine pia, na "kuongeza ili kuona nini kingeweza kutokea wakati wa mawimbi ya joto, au nini kilitokea", alisema. Mwanzoni mwa mwezi huu, yeye na timu ya watafiti walichapisha matokeo ya mfano ambao walitumia kutabiri harakati za wanyama 14 wa baharini - aina ya mamalia, ndege na samaki - katika Pasifiki ya Kaskazini wakati wa mawimbi ya joto ya 2014, 2015, 2019 na 2020. Kile walichogundua ni "tofauti kubwa ya majibu katika mawimbi ya joto", alisema. Kwa mfano, wakati wa joto la mwaka wa 2014 na 2015, samaki aina ya bluefin na albacore walihamia kaskazini-magharibi. Mwaka 2019 na 2020 walihamia kusini mashariki. Watafiti pia waligundua kwamba spishi tofauti-tofauti ziliitikia... vizuri, kwa njia tofauti. "Kwa hivyo ikiwa utaangalia nyangumi wa bluu dhidi ya albatros, watafanya mambo tofauti, "alisema, akibainisha kwamba uchunguzi kama huo haukuonekana kabla kwa sababu masomo mengi ya mawimbi ya joto ya baharini yalilenga mnyama mmoja katika wimbi moja la joto. """ Alexa Fredstone, profesa msaidizi wa sayansi ya bahari katika Chuo Kikuu cha Santa Cruz, alisema: "Tuna hadithi kadhaa ambazo kwa mtu mmoja zina maana kuhusu jinsi jamii fulani zilivyoathiriwa", alisema. "Lakini kila hadithi ni ya kipekee na jambo la kawaida ambalo tunaona ni wakati kuna wimbi la joto la baharini, hatuoni majibu yoyote ya usawa katika mfumo wa ikolojia. ""Alisema mawimbi ya joto yamekuwa na athari mbaya wazi kwa mifumo ya ikolojia ya maji ya chini, kama misitu ya kelp na matumbawe." Lakini unapofika chini zaidi katika safu ya maji, mambo huwa meusi zaidi. Alishirikiana na timu ya wanasayansi wa bahari na data kutoka Amerika Kaskazini na Ulaya kuangalia athari za mawimbi ya joto baharini kwenye samaki kati ya 1993 na 2019. Hawakupata athari dhahiri - chochote zaidi ya kile unachotarajia na kutofautiana kwa asili. "Kilichoshangaza kuhusu hili ni kwamba masomo yameonyesha kwamba, kwa miongo kadhaa, samaki wanabadilika kuelekea ncha za juu kwa wastani" wakati joto la bahari linapopanda kutokana na ongezeko la joto duniani, alisema. <unk>Kwa hiyo tunajua kwamba kuna <unk> ishara ya hali ya hewa ya muda mrefu. "Kwa samaki kama samaki, ambao wanahitaji mazingira ya baharini na maji baridi, hali ni tofauti kidogo, na mchanganyiko wa mawimbi ya joto katika Pasifiki ya Kaskazini juu ya sayari ya joto, ni neema kwa spishi zingine, na msiba kwa wengine, ""alisema Nate Mantua, mwanabiolojia wa samaki na NOAA." "Mwaka huu, joto la joto katika maeneo kama vile Ghuba ya Alaska au pwani ya Pasifiki, ""kuvunja"" usambazaji wa chakula haki katika msingi, na kusababisha mnyororo wa chakula mrefu na aina ya chakula kidogo lishe, ""kwa salmon." Lakini "ukienda kaskazini vya kutosha", joto linaweza kuwa linafaidi samaki kama vile Bering Sea na Bristol Bay sockeye salmon, alisema. Katika miaka kumi iliyopita, samaki hawa walikuwa na <unk>kimbele kubwa... mavuno makubwa milele. Samaki milioni hamsini waliokolewa. <unk> Alisema kwamba uvuvi wa samaki wa Pasifiki wa Urusi mwaka huu pia <unk> haujawahi kuwa juu. Ni nje ya chati, lakini ni karibu kabisa kutokana na salmoni waridi kutoka Urusi na idadi ya hisa katika Bristol Bay. Mahali pengine popote mambo si mazuri. <unk> Mbali zaidi kaskazini kuliko hiyo? "Hiyo ni wrinkle ya kuvutia", Mantua alisema. "Kama vile samaki hao wamekuwa wakifanya vibaya sana kwa miaka 20 iliyopita, ""alisema, ""inawezekana ni kwa sababu ya mchanganyiko wa matatizo katika mtandao wa chakula cha baharini kaskazini mwa Bahari ya Bering, pamoja na katika mazingira yao ya maji baridi.""" "Wana uhamiaji mrefu sana kupitia ndani ya Alaska na inaweza kuwa moto sana huko wakati wa majira ya joto", alisema. "Wachunguzi wa NOAA, Welch, na wengine, wanatarajia kwamba ""mfano wa utabiri wa ikolojia"" utasaidia." Kwa bahati nzuri, kuna maeneo yanayoonekana kuwa yenye nguvu zaidi dhidi ya mawimbi ya joto kuliko mengine. Ryan Walters, mtaalamu wa bahari katika Chuo Kikuu cha California, alisema maeneo yenye mvuke mkali, kama vile eneo la baridi kwenye pwani ya California, yanaonekana kuwa hayaathiriwi sana na mawimbi ya joto kuliko maeneo mengine ya bahari, na kuweza kutoa kimbilio la baridi kwa wanyama wanaotafuta kuepuka joto. "Inaweza kuwa kwamba mifuko hii ndogo kando ya pwani, ambapo tuna upwelling hii... inaweza kuwa mahali ambapo wanyama wa baharini wanaweza kutafuta kimbilio kutoka maji ya joto mahali pengine, "alisema.