Has the Gulf Stream Slowed or Shifted in the Altimetry Era?

The Gulf Stream (GS) is expected to slow and shift poleward over the next century due to climate change. We investigate whether such changes are already observable in the altimetric record (1993–2018) using along-track altimetry. Decadal trends in latitude, speed, transport, and width are calculated in stream-following coordinates to avoid spurious signals due to changes in higher-frequency GS variability. Statistically significant trends are few and apparently randomly distributed. Further, small changes to the length of the record lead to large changes in the trends and their significance. These results suggest that the current observations are insufficient to detect significant trends in these metrics. If the trends continue at the current rate, detection of trends at more than half of the altimetry tracks would require 22–23 additional years of observations for latitude and transport and 44 additional years for speed.