Tropical Decadal Variability and the Rate of Arctic Sea Ice Decrease

The trend for cold-season (November-December-January-February, NDJF) decreases in Arctic sea ice extent from 2000 to 2014 was about a factor of two larger than the 1979-2000 trend, and the warm-season (June-July-August-September, JJAS) trend was about a factor of three larger. Sensitivity experiments with an atmospheric model show that a negative convective heating anomaly in the tropical Pacific, associated with the negative Interdecadal Pacific Oscillation phase after 2000, produces an atmospheric teleconnection pattern over the Arctic comparable to the observations in NDJF but not JJAS. A positive convective heating anomaly over the tropical Atlantic, associated with warming sea surface temperatures there in the 2000-2014 period, produces a teleconnection pattern over the Arctic comparable to the observations in JJAS but not NDJF. Thus, the observed anomalously strong Arctic surface winds and sea ice drifts after 2000, which produced accelerated decreases in sea ice extent, likely had contributions from decadal-time scale variability in the tropical Pacific and Atlantic. Plain Language Summary Why did the trend of Arctic sea ice loss accelerate after about 2000? We show that a combination of decadally varying tropical sea surface temperatures in the Pacific and Atlantic drove seasonally dependent patterns of stronger surface winds and sea ice drifts over the Arctic that produced accelerated decreases of Arctic sea ice concentrations after 2000.