A Stable Gulf Stream in the Past Two Decades

In addition to meridional heat transport and climate, the transport of Gulf Stream (GS) has also been related to sea level on the east coast of US. In particular, Ezer (2013) has argued that recent sea level rise is related to a decadal-scale reduction in GS transport. This result is at odds with observations of GS transport at the Oleander Line, which show no significant change in GS transport over the past two decades (Rossby et al., 2014). The present study seeks to resolve this discrepancy by analyzing GS surface-layer transport and cross-stream velocity structure from along-track sea surface height (SSH) at 11 altimetric tracks between 79°W and 55°W. Total GS transport at each track is estimated from a ratio between the total transport and surface-layer transport derived from HYCOM reanalysis product. No significant difference of the cross-stream structure and transport can be found between the first and last decades of 1993-2015. GS transport therefore appears to be stable over the past two decades, and the sea level rise on the east coast of US is unlikely to be related to a long-term trend in GS transport.

Reference

Ezer, T., 2013. Sea level rise, spatially uneven and temporally unsteady: Why the U.S. East Coast, the global tide gauge record, and the global altimeter data show different trends: SPATIAL AND TEMPORAL SEA LEVEL RISE. Geophysical Research Letters 40, 5439-5444. https://doi.org/10.1002/2013GL057952

Rossby, T., Flagg, C.N., Donohue, K., Sanchez-Franks, A., Lillibridge, J., 2014. On the long-term stability of Gulf Stream transport based on 20 years of direct measurements. Geophysical Research Letters 41, 114-120. https://doi.org/10.1002/2013GL058636