Abstract: Rapid decline in Arctic sea-ice coverage suggests that the pathway and intensity of the Arctic Transpolar Drift (TPD) have changed evidently. In this study, we calculate sea surface stress in the Arctic by including the effects of both sea ice and surface ocean geostrophic currents to investigate variation in intensity and source region of the TPD. The TPD is stronger in winter than in summer and strongest (weakest) in December (September). During 2003–2014, the annual mean velocity of the TPD increased, and the source area shifted westward from the East Siberian Sea to the Laptev Sea. The main factor affecting interannual variation of the TPD intensity is sea ice coverage; the higher the sea ice coverage, the weaker the TPD. The main factor affecting seasonal variation of the TPD intensity is the seasonal variation of surface winds. In winter (summer), the surface winds and sea surface stresses are strong (weak), as is the TPD intensity. Changes in surface winds and sea ice coverage jointly affect the source region of the TPD. During 2003–2014, the dominant factor controlling the westward movement of the TPD source was the Beaufort High, which moved southwestward from the Beaufort Sea toward the Russian coast,causing the TPD source to move westward. Rapid decline of sea ice coverage also caused westward movement of the TPD source. As sea ice melts, sea surface stresses increase, and the Beaufort Gyre expands from the Canada Basin to the East Siberia Sea, triggering the TPD source to move westward.

Key words: Arctic Ocean, transpolar drift, sea surface stress