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Icebergs, the colossal floating masses of freshwater ice that drift across the world’s oceans, are shaped by the temperature of the water that surrounds them. At the surface, the ice is in thermal equilibrium with its environment; the temperature inside can be markedly colder, creating a gradient that governs how the iceberg erodes over time.
Unlike the plain ice cube you might keep in your freezer, an iceberg sits in saltwater. The dissolved salts lower the freezing point of the ocean, so even when the water is at 0 °C (32 °F), the ice can still melt. When temperatures rise above the brine’s freezing point, the rate of melting outpaces any new ice that might form, accelerating the iceberg’s decay.
While the outer layer matches the ambient water temperature, the interior can be as cold as –15 °C to –20 °C (5 °F to –4 °F) near the coast of Newfoundland and Labrador. This steep gradient means that the ice at the core is largely insulated, but the warmer exterior is where most mass loss occurs.
Water temperatures fluctuate dramatically with latitude and time of year. In July, for instance, the waters off mid‑Alaska can reach 8 °C (46 °F), whereas winter temperatures may drop to –2 °C (28 °F). Further south, British Columbia’s July waters sit between 12 °C and 16 °C (53 °F to 61 °F). Icebergs that remain within the cold polar regions melt slowly; once they venture into the Atlantic or Pacific, they encounter warmer waters and break apart more quickly.
Understanding these temperature dynamics is crucial not only for maritime safety but also for studying climate change impacts on polar ice masses.
