An esteemed NOAA expert cautions that nearly every ocean on Earth is experiencing "unusual warmth", which has contributed to the intense heat that has scorched a large portion of the Northern Hemisphere this summer.

Stats NZ's Stuart Jones said in a statement, "Even small rises in temperature can disrupt marine ecosystems, cause some species to relocate, and increase disease risks," adding, "It also contributes to sea-level rise as the warmer water expands."

The Atlantic region, where the most dangerous storms of this type usually form, is seeing record-warm ocean temperatures, which hurricane analysts say might result in a very busy hurricane season. Some of those fears came true with Hurricane Beryl, which broke many early season records.

Zack Labe, a researcher at NOAA's Geophysical Fluid Dynamics Laboratory, explained in an email that "this year has observed truly remarkable spatial coverage of above-average sea surface temperatures."

"The record warmth globally over the last year has been felt both in the atmosphere and in the ocean, which can be directly linked to the influences of human-caused climate change," he added.

June, in fact, ushered in a record-breaking 15 months of record-breaking ocean temperatures, and July may break that streak with the second-warmest rating.

Read more: Mediterranean ecosystem suffering 'marine wildfire'

The world is experiencing its hottest three days on record, starting on Sunday, due to the abnormally warm waters.

Both the Northern and Southern Hemispheres' ecosystems have been influenced by the rising ocean temperatures. However, Labe points out that the northern half of the Atlantic and Pacific Oceans currently exhibit the most abnormal warmth.

Marine heat waves, which Labe describes as "similar to heatwaves we feel in the atmosphere" but happen in ocean waters instead, are partially responsible for the warmth. Marine heat waves are characterized as periods of continuous anomalously warm ocean temperatures.

"These can have major impacts to marine ecosystems, such as through coral bleaching or loss of marine life, and can even affect coastal towns and communities," Labe said.

Coral reefs in the Florida Keys were nearly destroyed by the record-breaking marine temperature of last July. After a brief period of cooling, the temperature is currently rising once more.

In a call with reporters this week, Katey Lesneski, the monitoring coordinator for NOAA's Mission: Iconic Reefs program, stated that there is extensive evidence of coral "paling" but not yet bleaching.

Because the southern part of the Iconic Reefs program is over bleaching thresholds and the northern portions are getting close to them, scientists are working on plans to introduce heat-hardened species to the coral reefs and transplant species from other locations.

According to Lesneski, many "of these sites are above that critical threshold" where you start to see them experience heat stress."

According to data released this month by Stats NZ, New Zealand's annual sea temperatures are at record highs, rising 0.16°C–0.26°C (0.28°F–0.47°F) every decade since 1982. According to the government office, 2022 or 2023 were the hottest years ever recorded in every maritime and coastal region of the island nation.

Read more: Climate endgame: Human extinction is inevitable

Although the effects of such extreme weather events were poorly understood, Christopher Cornwall, from the Victoria University of Wellington's School of Biological Sciences, noted in a statement that previous intense marine heat waves had killed southern bull kelp in regions along NZ's coastal South Island.

He explained the high probability "that both the background warming and more frequent, intense, and longer marine heatwaves are already working to permanently alter these marine ecosystems" within New Zealand. 

The Adriatic Sea near Dubrovnik in southern Croatia had a temperature of 85.5°F on July 15, which, if verified, would be the highest temperature ever recorded. The country is currently experiencing a heat wave.

Oceanographer Ivica Vilibic of the Rudjer Boskovic Institute in Split told Reuters that the Adriatic was about 5°C warmer overall than it usually is at this time of year.

"There are different effects [from climate change]. For example, there are species which like a warm ocean, as in the Red Sea. So there are lot of species that are already coming to the Adriatic, and more will come," he added.

Across the Central Pacific Ocean, there are cooler sea surface temperatures, which, according to Labe, is indicative of an impending La Niña event. Within a brief period of time, this can somewhat lower world temperatures.

Scientists are observing a long-term increase in sea surface temperatures in the tropical Pacific Ocean, despite this natural cycle of ocean temperatures in this region.

Research this year "suggests that we may need to consider using alternative definitions for assessing La Niña and El Niño conditions due to this long-term warming of the ocean from climate change," Labe continued.

Georgia Grant, from New Zealand's Geological and Nuclear Sciences Limited, released a statement saying that as the atmosphere "continues to warm with increasing greenhouse gases," the surface of the ocean naturally warms with it.

She pointed out that 90% of the additional heat from the buildup of greenhouse gases brought on by human activity is absorbed by the oceans.

The air temperature would be 20°C (36°F) greater "if we didn't have the ocean," Grant revealed.