The impact of remote temperature anomalies on the strength and position of the Gulf Stream and on coastal sea level variability: a model sensitivity study

A regional numerical ocean model of the Gulf Stream (GS) and the US East Coast was used to conduct sensitivity experiments of the dynamic response to temperature anomalies originated at different Atlantic locations. In a series of experiments, temperature anomalies were injected into the model domain through inflow boundary conditions at either the Florida Current (FC), the Slope Current (SC), or the Sargasso Sea (SS), while holding all other inflows/outflows unchanged. The strong currents and meso-scale variability of the GS system result in fast transport of anomalies throughout the model domain and immediate response within days. During a period of 60 days, remote temperature anomalies of +/- 2 degrees C induced about 5-12 cm change in coastal sea level, about 0.5-1.0 ms(-1) change in velocity, and about 30-50 km shift in the GS position, and a significant increase in kinetic energy of the whole GS system. Warm anomaly entering into the GS from the south through the FC had the strongest impact, strengthening the GS and temporally lowering coastal sea level by as much as similar to 10 cm, compared with coastal sea level drop of similar to 2-3 cm when the same warm anomaly was coming from the SS. Cold or warm anomalies coming from the north through the SC caused a large shift in the GS path, which moved onshore in the Mid-Atlantic Bight (MAB) and offshore in the South Atlantic Bight (SAB). Observations taken in 2017 when 3 hurricanes disrupted the GS flow show similar links between temperature anomalies, the GS, and coastal sea level, as in the idealized model simulations. The results demonstrated how temperature anomalies due to storms or uneven climate warming can cause variations on the coast and increased kinetic energy near western boundary currents. Since coastal sea level is positively correlated with temperature, but negatively correlated with the strength of the GS, the non-linear combination of the two factors can result in unexpected spatiotemporal variability in coastal sea level. The study provides better understanding of how remote signals affect the coast.

Automated summary

A numerical model of the Gulf Stream and the US East Coast was used to study the sensitivity of the dynamic response to temperature anomalies from different locations in the Atlantic. The results showed that temperature anomalies can cause changes in coastal sea level, velocity, and the position of the Gulf Stream, as well as increased kinetic energy. The impact varies depending on the location and type of anomaly.