Dataset: Towed ADCP data from Isla Natividad collected in July of 2018

All files are from the East Side of the Island (July 25-27, 2018), except for "West_Side_0_000_ASC.TXT" (Jul 28-29, 2018). The files are readily readable and their format follows the default from the WinRiver software of Teledyne Instruments.

Location: The study was performed on Isla Natividad, found off Punta Eugenia, the most prominent point in the middle of the western coast of the Baja California peninsula (Fig. 1a in Valle-Levinson et al., 2022), near the southernmost limit of the California Current.

Methods & Sampling:

Data were collected over two headlands at either side of Isla Natividad (Fig. 1b 'Location' in Valle-Levinson et al., 2022). The sampling strategy consisted of three offshore transects around headlands on the eastern (1E, 2E, 3E) and western (1W, 2W, 3W) coast of the island (Fig. 1b in 'Location' in Valle-Levinson et al., 2022). Both headlands were located over the southern half of the island (Fig. 1b  'Location'  in Valle-Levinson et al., 2022) but only the western headland had dense kelp (Macrocystis pyrifera, LSID urn:lsid:marinespecies.org:taxname:232231)  forests around it. The objective of the sampling strategy was to capture variations of the flow around the headland throughout full tidal cycles. Because the study area is dominated by mixed tides with semidiurnal dominance, sampling was designed to cover at least one 25-hr cycle. This strategy also allowed the separation of tidal and residual or subtidal signals (e.g., Valle-Levinson and Atkinson, 1999) to identify flow fields typical of headland upwelling. Wind conditions should be sufficiently weak (<7-8 m/s) to allow towed-ADCP data collection. In fact, wind conditions during ADCP sampling averaged <3 m/s, according to data from a station 20 km away, at Cedros Island.

Instruments:
Each transect was covered by Acoustic Doppler Current (ADCP) profiles of water velocity, acoustic backscatter, and values of surface water temperature. Raw data were recorded at 2 Hz while the ADCP was towed on a catamaran on the side of a boat from the local fisher cooperative. Acceptable data were trimmed to allow 3-beam solution values with >70% good and <100 m2/s transport. On the east side of the island, transects were traversed at ~ 2m/s over waters with minimal kelp presence.

Problems/Issues:

East-side transects were covered on July 25th, 2018, for 12 h, because of an emergency for the fishing cooperative, and then re-occupied from July 26 to July 27, 2018. Transects on the west side were sampled over dense kelp forests (see photo on Figure 1b  in Valle-Levinson et al., 2022). Sampling was executed interruptedly, again because of cooperative emergencies, from July 28th to July 29th, 2018.

Deployment Description:

Data were collected with a local cooperative boat over two headlands at either side of Isla Natividad, off the Baja California western coast . The sampling strategy consisted of three offshore transects around headlands on the eastern and western coast of the island. Both headlands were located over the southern half of the island but only the western headland had dense kelp (Macrocystis pyrifera) forests around it. The objective of the sampling strategy was to capture variations of the flow around the headland throughout full tidal cycles. Because the study area is dominated by mixed tides with semidiurnal dominance, sampling was designed to cover at least one 25-hr cycle between July 25 and 29, 2018. Chief scientist: Arnoldo Valle-Levinson.