Tides and long-term modulations in the Caribbean Sea

2012

J. Geophys. Res.

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[1] The seasonal sea level cycle has been investigated in the Caribbean Sea using altimetry and tide gauge time series from 27 stations and is characterized by large spatial variability. The coastal annual harmonic has amplitudes that range from 2 cm to 9 cm, peaking between August and October and semi-annual harmonic with maximum amplitude of 6 cm, with most stations peaking in April and October. The coastal seasonal sea level cycle contributes significantly at most areas to sea level variability and can explain the sea level variance up to 78%. The barometric effect on the coastal sea level seasonal cycles is insignificant in the annual component but dominant at 9 stations in the semi-annual cycle. The seasonal sea level cycle from 18 years of altimetry confirm the results obtained from the tide-gauges and allow us to identify some dominant sea level forcing parameters in the annual and semi-annual frequencies such as the Panama-Colombia gyre driven by the wind stress curl and the Caribbean Low Level Jet modulating the sea level in the northern coast of South America and linked to the local upwelling. The seasonal sea level cycle in the Caribbean Sea is unsteady in time, with large variations in amplitude and phase lag at most of the stations, where the 5-year amplitude in the coastal annual cycle can change over 6 cm in a 24 year period. The seasonal sea level cycle peaks about October when the probability of coastal impacts increases, especially in the northern coast of South America where the range is larger.

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Seasonal sea level cycle in the Caribbean Sea

Torres

2012

J. Geophys. Res.

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“…Five of the stations have records longer than 20 years, which permit the study of the temporal variability of the sea level extremes. The time series were described in detail by Torres and Tsimplis [2011]. However, the Cristobal record has been further extended to 2009 (Figure 1b).…”

Section: Methodsmentioning

confidence: 99%

“…The largest value is found in P. Spain. A significant part of the large extreme at this station is due to the tidal component (Table 1) which is larger at the boundaries between the Caribbean and Atlantic [Torres and Tsimplis, 2011]. Note the importance of mean sea level change for the maxima estimated at stations with large trends such as Cartagena, where the maximum observed sea level in a 49 year period (66 cm in Figure 2a) is 20 cm smaller after the mean sea level contribution at interannual frequencies is removed (Figure 2b).…”

Section: Spatial Distribution Of Sea Level Extremesmentioning

confidence: 99%

“…The Caribbean Sea is an eddy-rich region [Chelton et al, 2007] where eddies can generate sea level anomalies in the order of few decimeters [Alvera-Azcarate et al, 2009;Andrade and Barton, 2000], while the tidal contribution is small [Torres and Tsimplis, 2011]. Mesoscale eddies have been reported to be a main contributor to sea level extremes events at places where sea level variations are small [Firing and Merrifield, 2004].…”

Section: Introductionmentioning

confidence: 99%

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Sea level extremes in the Caribbean Sea

Torres

2014

JGR Oceans

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Sea level extremes in the Caribbean Sea are analyzed on the basis of hourly records from 13 tide gauges. The largest sea level extreme observed is 83 cm at Port Spain. The largest nontidal residual in the records is 76 cm, forced by a category 5 hurricane. Storm surges in the Caribbean are primarily caused by tropical storms and stationary cold fronts intruding the basin. However, the seasonal signal and mesoscale eddies also contribute to the creation of extremes. The five stations that have more than 20 years of data show significant trends in the extremes suggesting that flooding events are expected to become more frequent in the future. The observed trends in extremes are caused by mean sea level rise. There is no evidence of secular changes in the storm activity. Sea level return periods have also been estimated. In the south Colombian Basin, where large hurricane-induced surges are rare, stable estimates can be obtained with 30 years of data or more. For the north of the basin, where large hurricane-induced surges are more frequent, at least 40 years of data are required. This suggests that the present data set is not sufficiently long for robust estimates of return periods. ENSO variability correlates with the nontidal extremes, indicating a reduction of the storm activity during positive ENSO events. The period with the highest extremes is around October, when the various sea level contributors' maxima coincide.

Sea level extremes at the coasts of China

Feng

J. Geophys. Res. Oceans

2014

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Hourly sea level records from 1954 to 2012 at 20 tide gauges at and adjacent to the Chinese coasts are used to analyze extremes in sea level and in tidal residual. Tides and tropical cyclones determine the spatial distribution of sea level maxima. Tidal residual maxima are predominantly determined by tropical cyclones. The 50 year return level is found to be sensitive to the number of extreme events used in the estimation. This is caused by the small number of tropical cyclone events happening each year which lead to other local storm events included thus significantly affecting the estimates. Significant increase in sea level extremes is found with trends in the range between 2.0 and 14.1 mm yr 21 . The trends are primarily driven by changes in median sea level but also linked with increases in tidal amplitudes at three stations. Tropical cyclones cause significant interannual variations in the extremes. The interannual variability in the sea level extremes is also influenced by the changes in median sea level at the north and by the 18.6 year nodal cycle at the South China Sea. Neither of PDO and ENSO is found to be an indicator of changes in the size of extremes, but ENSO appears to regulate the number of tropical cyclones that reach the Chinese coasts. Global mean atmospheric temperature appears to be a good descriptor of the interannual variability of tidal residual extremes induced by tropical cyclones but the trend in global temperature is inconsistent with the lack of trend in the residuals.