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Table S1. Additional Supporting Information (Files uploaded separately) ... left panel (data recovery during CANEK 23) and from July 2012 to June 2013, right.
Geophysical Research Letters Supporting Information for Inter-annual variability in the Yucatan Channel flow Gabriela Athié(1), Julio Sheinbaum(1), Robert Leben(2), José Ochoa(1), Michael R. Shannon(2) and Julio Candela(1) (1) CICESE, Baja California, México (2) University of Colorado, Boulder, CO.

Contents of this file Figure S1 Figure 2S Table S1 Additional Supporting Information (Files uploaded separately) No files were uploaded separately

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Introduction The objective mapping method was used to interpolate the velocity component perpendicular to the section. The interpolation was done into a regular grid, from which transport calculation followed directly (Figures 1 and 2 of the main text). The statistics was assumed the same in each measuring period, but the instrument layout was slightly different, hence Figure 1S presents the error maps for the interpolation (percentagewise with respect to the signal standard deviation). 0

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−200 −400 −600

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Depth (m)

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Canek 23

Canek 29

2010−2011

2012−2013

86.5°W

86.0°W

85.5°W

85.0°W 86.5°W

86.0°W

85.5°W

85.0°W

Figure S1. Interpolation errors of velocity measurements, from May 2010 to May 2011, left panel (data recovery during CANEK 23) and from July 2012 to June 2013, right panel (CANEK 29). The maps are presented as percentage of the signal standard deviation. Black dots (with the exception of dots at surface) represent the vertical distribution of the punctual measurements by the ADCPs and current meters installed at each period.

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Geostrophic velocities derived from CTOH along-track altimetry data are used to compare and complement the moored observations discussed in the main body of the paper. The CTOH data in use is the set of files ctoh.sla.filt.ref.TP+J1+J2.gom.###.nc where ### stands for the track identifier. As explained in the document methods_processing_coastalti.pdf available at http://ctoh.legos.obs-mip.fr/products/ coastal-products/documents, the data files are reprocessed records at 1-Hz (i.e. 6-7 km along-track spacing) with several corrections included. Roblou et al (2011) offer further information about such data. These data estimate sea level anomalies with tides and highfrequency wind induced contributions removed. The removal of such high-frequency contributions, via barotropic numerical models, and error removal algorithms, have the goal of providing reliable de-aliased altimeter data even close to shore, as this is a wellknown weakness of the gridded AVISO data. On these sea level anomalies, 20 km alongtrack oscillations have been filtered-out. Therefore, these measurements are not high frequency nor (very) high-wavenumber signals but suitable for specifying low-frequency fluctuations. The analyzed tracks 167 and 102 cross the flows exiting the Gulf, tracks 178 and 243 cross the region where the cable measurements are available, and track 178 also crosses the Old Bahama Channel (OB). The analysis allows comparison of surface flow variability exiting the gulf (tracks 167, 102), which by the closed nature of the gulf necessarily transit through Yucatan Channel, with flow through OB that also contributes to the Gulf Stream at 27° N (cable measurements). These flows provide further evidence that the 1999–2001 period had the largest negative geostrophic velocity anomalies exiting the Gulf and across the Florida Straits, and the largest compensating anomaly across OB.

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Figure S2. Top panel: map of the region showing CTOH satellite tracks on which geostrophic velocity anomalies for the Florida Straits and Old Bahama (OB) channel and were calculated using sea level differences between the dots marked on each track. Contour line marks the 500 m isobath. Track number is indicated near the lower end of each track. The red vectors specify the direction of the geostrophic component shown. Bottom panel: blue dots indicate the geostrophic velocity anomalies every ~10 days for the sector 178B with an offset of 0.5 m/s, and blue lines below indicate averages over 1.74 year contiguous periods. The red lines mark the 1999-2001 period of low CANEK transport measurements (lasting 1.74 years). This period has the largest anomaly across the Florida straits and a partial compensating anomaly across OB.

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Table 1S provides additional information regarding the Yucatan Channel transport proxy obtained from regressing sea level differences across the channel with the mooring measurements (Figure 4, main text). Regressions were carried out using daily, monthly and quarterly data as well as 120-days and full CANEK deployment averages (between 360-520 days depending on deployment). Cuba-Yucatan sea level difference is estimated using the gridded AVISO product. Transport proxies based on lower frequency (120days) fits provide better agreement with the mooring transports (Figure 4, main text) and suggest substantial inter-annual variability during the 1993-2013 period. Table S1. Slope (a) and ordinate (b) values from the regression analyses calculated between the transport measurements and AVISO sea-level differences at Yucatan Channel (86.875°W, 21.625°N and 84.625°W, 22.125°N). Different approaches (data averages) were evaluated: daily, monthly, quarterly, 120-days and full CANEK deployment periods (1999-2001, 2010-2011 and 2012-2013). These slope and ordinate values were used to estimate a transport proxy for the 20 year AVISO data set; the mean and standard deviation for each of the 20-years transport estimates are also indicated. y = ax + b Daily data Monthly data Quarterly data 120-days CANEK periods

a

b

0.1431 0.2200 0.2376 0.343 0.7491

18.7017 15.516 14.515 10.385 -6.5751

Mean (Sv) (1993-2013) 25.2 25.6 25.3 25.9 27.4

Standard deviation 1.2 1.9 2.0 2.9 6.3

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