Answer:
an ocean current that brings warm southern waters north
Step-by-step explanation:
The north Atlantic Drift played a major role in warming up the European's temperature during their tropical season.
The current originated from Gulf of Mexico and move all the way to Greenland and Iceland. When the current reach there, it eventually cools and sinker to the sea floor.
The scientist predicted that this current has been around for more than half-million years. Without it, the average temperature that people in Europe and north America have during summer will be actually closer to the temperature in autumn or even winter.