Jet Streaks in the Gulf Stream

Mesoscale alongstream speed changes of the Gulf Stream are diagnosed from an array of current meters at depths 400, 700, and 1000 m, near 68°W, during the development of steep [ratio of “amplitude” to “wavelength” O(1)] meanders. Speed maxima (jet streaks) are generally found between trough and crest axes in steep meanders with local speed minima near the trough and crest axes. Speed changes along streamlines can be quite dramatic. Speed changes along the jet axis, between jet streaks and local minima in excess of 0.60, 0.40, and 0.35 m s−1, are observed at depth 400, 700, and 1000 m, respectively. This is in comparison with peak speeds in a frontal coordinates system mean of 1.22, 0.67, and 0.28 m s−1, at depth 400, 700, and 1000 m, respectively, from a previous study. The presence of the jet streaks can be explained kinematically as a superposition of the Gulf Stream and barotropic vortices. The development of these jet streaks in relation to the developing steep meanders differs from the canonical picture of jet streak/baroclinic wave development in the atmospheric jet stream in that the jet streaks in the Gulf Stream are predominantly fixed in place with respect to meanders as they steepen

Inverted Echo Sounder Telemetry System Report

From August 1989 until August 1990, a simple acoustic telemetry system was used for obtaining real-time data from 5 Inverted Echo Sounders (IESs) deployed in the SYNOP inlet array in the Gulf Stream east of Cape Hatteras. Every 24 hours, each IES calculated a representative travel time from a set of 48 measurements (τ), and telemetered that value to a listening station on Bermuda. From the received data, a daily time series of the depth of the 12oC isotherm (our proxy for main thermocline depth) over each IES was calculated. The position of the Gulf Stream North Wall through the IES array was calculated on a daily basis from the thermocline depth information at each IES site. The telemetry system is based on encoding data as a time delayed broadcast acoustic signal: the delay of the time of broadcast of the signal, with with respect to a reference time, is proportional to the data value. The changes in delay time, from one broadcast signal to the next, are recorded at a remote receiving station. The IESs were recovered in August 1990, with the exception of the one at site B2. The telemetered data from the IES at site B2 was, however received at Bermuda. The RMS agreement between thermocline depths, as calculated from the data on tape from the recovered IESs and as calculated from the received telemetry data, is 20 m. This compares favorably with the 19 m uncertainty in calibrating the τs as a measure of the thermocline depth. The RMS agreement between the position of the Gulf Stream path through the IESs as calculated from the tape data and the telemetry data is 5 km. This telemetry system is not IES specific. It could be used with other appropriately modified oceanographic instruments, such as current meters and pressure sensors

Were Multiple Stressors a \u27Perfect Storm\u27 for Northern Gulf of Mexico Bottlenose Dolphins (Tursiops truncatus) in 2011?

An unusual number of near term and neonatal bottlenose dolphin (Tursiops truncatus) mortalities occurred in the northern Gulf of Mexico (nGOM) in 2011, during the first calving season after two well documented environmental perturbations; sustained cold weather in 2010 and the Deepwater Horizon oil spill (DWHOS). Preceding the stranding event, large volumes of cold freshwater entered the nGOM due to unusually large snowmelt on the adjacent watershed, providing a third potential stressor. We consider the possibility that this extreme cold and freshwater event contributed to the pattern of perinatal dolphin strandings along the nGOM coast. During the 4-month period starting January 2011, 186 bottlenose dolphins, including 46% perinatal calves (nearly double the percentage for the same time period from 2003-2010) washed ashore from Louisiana to western Florida. Comparison of the frequency distribution of strandings to flow rates and water temperature at a monitoring buoy outside Mobile Bay, Alabama (the 4th largest freshwater drainage in the U. S.) and along the nGOM coast showed that dolphin strandings peaked in Julian weeks 5, 8, and 12 (February and March), following water temperature minima by 2-3 weeks. If dolphin condition was already poor due to depleted food resources, bacterial infection, or other factors, it is plausible that the spring freshet contributed to the timing and location of the unique stranding event in early 2011. These data provide strong observational evidence to assess links between the timing of the DWHOS, other local environmental stressors, and mortality of a top local predator. Targeted analyses of tissues from stranded dolphins will be essential to define a cause of death, and our findings highlight the importance of considering environmental data along with biological samples to interpret stranding patterns during and after an unusual mortality event

Evidence of Sea Level Rise At the Peruvian Coast (1942-2019)

The present work aims to analyze the variability of the sea level of the Peruvian coast with time series over a long observation period (Seventy-eight years, from 1942 to 2019). Data came from the Talara, Callao and Matarani tide gauge stations located at the north, center and south of the coast. Variations of sea level as well as air and seawater surface temperature were analyzed. Among the different scenarios studied, a sea level rise of 6.79, 4.21 and 5.16 mm/year for Talara, Callao and Matarani, respectively was found during the 1979–1997 nodal cycle. However, these results decreased significantly during the next cycle (1998–2016) until values of 1.53, 2.16 and 1.0 mm/year for Talara, Callao and Matarani, respectively. Thus, it has been demonstrated that sea level rise are highly dependent on the time interval chosen. Moreover, large interannual changes of up to 200 mm/year are observed, due to recurring phenomena, such as “El Niño”. On the other hand, the trends obtained are slightly lower than those shown by the IPCC up until 2006 but significantly higher values have been observed. Finally, the results presented herein show the necessity of a local study of the sea level variability at the coastal areas

Autonomous Seawater \u3ci\u3ep\u3c/i\u3eCO\u3csub\u3e2\u3c/sub\u3e and pH Time Series From 40 Surface Buoys and the Emergence of Anthropogenic Trends

Ship-based time series, some now approaching over 3 decades long, are critical climate records that have dramatically improved our ability to characterize natural and anthropogenic drivers of ocean carbon dioxide (CO2) uptake and biogeochemical processes. Advancements in autonomous marine carbon sensors and technologies over the last 2 decades have led to the expansion of observations at fixed time series sites, thereby improving the capability of characterizing sub-seasonal variability in the ocean. Here , we present a data product of 40 individual autonomous moored surface ocean pCO2 (partial pressure of CO2) time series established between 2004 and 2013, 17 also include autonomous pH measurements. These time series characterie a wide range of surface ocean carbonate conditions in diffferent oceanic (17 sites), coastal (13 sites), and coral reef (10 sites) regimes. A time of trend emergence (ToE) methodology applied ot the time series that exhibit well-constrained daily to interannual variability and an estimate of decadal variability indicates that the length of sustained observations necessary to detect statistically significant anthropogenic trends varies by marine environment. The ToE estisites, and 9 to 22 years at the coral reef sites. Only two open ocean pCO2 and pH range from 8 to 15 years at the open ocean sites, 16 to 41 years at the coastal sites, and 9 to 22 years at the coral reef sites. Only two open ocean pCO2 time series, Woods Hole Oceanographic Institution Hawaii Ocean Time-series Station (WHOTS) in the subtropical North Pacific and Stratus n the South Pacific gyre, have been deployed longer than the estimated trend detection time and, for these, deseasoned monthly means show estimated anthropogenic trends of 1.9 ± 0.3 and 1.6 ± 0.3 μatm yr-1, respectively. In the future, it is possible that updates to this product will allow for the estimation of anthropogenic trends at more sites; however, the product currently provides a valuable tool in an accessible format for evaluating climatology and natural variability of surface ocean carbonate chemistry in a variety of regions. Data are available at https://doi.org/10.7289/V5DB8043 and https://www.nodc.noaa.gov/ocads/oceans/Moorings/ndp097.html (Sutton et al., 2018)