The correct option is They bend towards the north..
Explanation
Isotherms are lines connecting points of equal temperature. While they generally follow latitudes, they deviate due to the differential heating and cooling of land and water bodies, as well as the influence of ocean currents. This deviation is most pronounced in the Northern Hemisphere due to the large concentration of landmasses.
Detailed Analysis:
- Differential Heating: In January, it is winter in the Northern Hemisphere. Land surfaces cool down much more rapidly than the oceans. Consequently, at a given latitude, the temperature over the ocean is higher than that over the continent.
- Direction of Bend: To connect points of equal temperature, the isotherm must shift towards the pole (where temperatures are generally lower) when moving from the colder land to the warmer ocean. Therefore, over the oceans, the isotherms bend towards the north (poleward).
- Role of Ocean Currents: In the North Atlantic Ocean, this effect is intensified by the presence of the warm North Atlantic Drift (an extension of the Gulf Stream). This current transports warm water to higher latitudes, causing the isotherms to bend sharply towards the north.
- Contrast with Continents: Conversely, over the continents (such as North America and Eurasia), the isotherms bend towards the south (equatorward) during January because the land is colder.
Key Takeaway:
In the Northern Hemisphere winter, isotherms bend towards the north (poleward) over oceans and towards the south (equatorward) over continents.