A well-defined ocean warming trend originating off the United States East Coast is likely from super-heated and methane-enriched fluids emitted from numerous seafloor hydrothermal vents/hot springs (see figure 1 after the jump).
Supporting evidence: This trend has shown up on shallow Sea Surface (SST) maps since their advent in 1997 and has likely been present for thousands of years.
Study Excerpt: "Ilyinskaya et al. recorded the first atmospheric gas emission rate measurements from Katla, one of Iceland’s largest active volcanoes. This massive ice-covered caldera, which last erupted a century ago, was previously assumed to be a relatively minor emitter of CO2, but the new results suggest otherwise...The results indicate that Katla emits 12–24 kilotons of CO2 per day, which is more than double previous estimates of the emission rate of CO2 from all volcanic and geothermal sources in Iceland combined (2.7–5.8 kilotons per day)"
"These findings suggest that subglacial volcanoes—the emissions of which have not been considered in much detail, historically—may be major emitters of carbon dioxide. Because of this, their contributions to the global volcanic CO2 budget may have been underestimated."
“The politics of this were impossible a few years ago. But not so much now,” said Rafe Pomerance, chairman of the environmental alliance Arctic 21 and a four-decade advocate of increased action on global warming. “If we think the problem of climate change is catastrophic, how can we say that we can’t at least consider this as an option?” ...
Researchers have envisioned duplicating the phenomenon by launching jets equipped to fly to 70,000 feet, the lower reaches of the stratosphere, where they would release a sulfur compound. The effort would bleach blue skies a lighter color and make sunsets more vivid, while shielding Earth from some of the sun's rays. The flights would have to be numerous and long-running to create anything like the reflective power of the volcanic eruptions.
In the journal, the team wrote: “Through high-precision airborne measurements and atmospheric dispersion modelling, we show that Katla, a highly hazardous subglacial volcano which last erupted 100 years ago, is one of the largest volcanic sources of CO2 on Earth, releasing up to five percent of total global volcanic emissions.”