Consider the following statements:
Statement I: In January, in the Northern Hemisphere, the isotherms bend equatorward while crossing the landmasses, and poleward while crossing the oceans.
Statement II: In January, the air over the oceans is warmer than that over the landmasses in the Northern Hemisphere.
Which one of the following is correct in respect of the above statements?
Explanation
Isotherms are lines connecting points of equal temperature on a map. Their bending pattern reveals the temperature contrast between land and ocean surfaces across different seasons.
Statement I is correct. In January, the Northern Hemisphere experiences winter. Large landmasses such as Eurasia and North America cool down rapidly, resulting in significantly lower temperatures over land. This causes isotherms to bend equatorward (southward) while crossing continents — reflecting the colder conditions. In contrast, oceans such as the North Atlantic and North Pacific retain heat for longer, keeping temperatures relatively higher. This causes isotherms to bend poleward (northward) while crossing oceans. Warm ocean currents like the Gulf Stream further amplify this effect by raising the temperature of surrounding air over the Atlantic.
Statement II is correct and directly explains Statement I. The reason for this contrasting isotherm behaviour lies in the specific heat capacity of water. Water has a much higher specific heat capacity than land, meaning it absorbs and releases heat more slowly. As a result, in winter (January), oceans cool down far more slowly than adjacent landmasses, and the air over oceans remains warmer than the air over continents. This temperature contrast between land and ocean is the direct cause of the isotherm bending pattern described in Statement I — equatorward over cold landmasses and poleward over relatively warmer oceans.
Therefore, both statements are correct and Statement II explains Statement I.