Climate change has driven the ocean—Earth’s primary heat sink—to absorb most of our planet’s excess warming. Sea surface temperatures are rising, fueling more frequent and intense marine heatwaves. The Atlantic Meridional Overturning Circulation (AMOC), key to global climate regulation, is weakening under a surge of polar meltwater, carrying serious implications for regional climates and sea levels. Polar regions are especially vulnerable: Arctic Sea ice is retreating rapidly, destabilizing ecosystems and endangering species like polar bears and penguins. Warming surface waters deepen the thermocline, curbing nutrient mixing and lowering productivity, with cascading effects on marine food webs. Meanwhile, species are shifting poleward, disrupting fisheries and economies that depend on stable, predictable ocean conditions.