## 3 Results
### Variability and Drivers
#### 3.3.1 EOF Analysis of the Raw Versus Detrended Data  
The first three PCs of the raw data explain approximately half (49%) of the variance. PC1_raw accounts for 36% of the variance and shows a distinct annual cycle peaking in August each year, superimposed on an upward linear trend (Figure 3b). The annual cycle is the dominant mode of variability in the Caribbean sea level record. When interannual variability in the annual amplitude is also considered, the upward linear trend is, for at least one year, close to the end of the record (e.g., 2015) when sea levels at their lowest in the annual cycle are comparable to or higher than the annual sea level maxima attained in the early record (e.g., 1995). (This also supports the idea of an accelerated rate of rise in the most recent decade represented in the data.) One implication of this is that, at the present rate of rise, the threat that arises from higher sea levels is becoming an all-year risk. When the linear trend is removed from the raw data, the first three PCs explain approximately 44% of the variance, with PC1_detrended accounting for nearly 30%. The timeseries for PC1_detrended is again dominated by the annual cycle with, however, the interannual variations in amplitude being more pronounced (Figure 3d). The spatial loadings for PC1_raw and PC1_detrended are almost identical (Figure 3a,c). This is due to the dominance of the annual cycle in both analyses. The spatial patterns show high values along the northern coast of South America; smaller but similarly signed loadings going northward from the Caribbean coast of South America over the Caribbean Sea and up to 17\({}^{\circ}\) N (the south coast of Jamaica); a maximum in the southwestern Caribbean between 10\({}^{\circ}\) N and 15\({}^{\circ}\) N and 80\({}^{\circ}\) W to 85\({}^{\circ}\) W; and high loadings in the northwest corner of the domain (Cayman Sea and toward the Gulf of Mexico). Figure 3a,c mirror the mean spatial variation of sea level across the Caribbean from dominant sea level forcing parameters with annual frequencies e.g., see Figure 1 of [17] or Figure 3a [21]. For example, higher sea levels just north of South America and in the southwest of the domain are associated with the Panama-Colombia Gyre, as well as the Caribbean Current [23]. The Caribbean Current transports significant volumes of water from the South Atlantic to join the Florida Current and, eventually, the Gulf Stream [34]. These southern Caribbean ocean circulatory features are largely wind driven, with annual variation in the strength of easterlies, which parallel the north coast of the south Caribbean, playing strong modulating roles [17; 21]. \begin{table}  
\end{table} 
Table 4: (**a**) Correlations between climate and ocean indices and the 2 leading PCs of the Raw, Detrended, Deseasoned, and Deseasoned & Detrended altimetry data. (**b**) As in (**a**), but for the leading PCs of the Raw and Detrended data for the summer season (June to September). The largest significant correlations for PC1_raw are with north Atlantic SST indices (Table 4a). These include +0.46 with Carib SST, +0.38 with the AMO, and \(-\)0.55 with the Pac-Atl gradient index, which includes north tropical Atlantic SSTs in its calculation. Sea level pressure in the vicinity of Jamaica also has a significant correlation (\(-\)0.4), and there are smaller significant correlations with the NINO3 (+0.22) and NINO3.4 (+0.25) regions. The north Atlantic SST associations likely derive from long term decadal trends which are common to both timeseries. SSTs in the tropical north Atlantic become much warmer after 1995 [68; 69], with the linear rise evident across all seasons, ranging from 0.1 \({}^{\circ}\)C/decade in spring to 0.2 \({}^{\circ}\)C/decade in winter and summer [69]. Warm Caribbean SSTs also associate with lower sea level pressures [70], and El Nino events influence the warm SST peaks observed in the trend [69; 71]. Caribbean SSTs seemingly play a significant role in regional sea level variability, especially in the long term.