Adrenal Response to Stimulation by Adrenocorticotropic Hormone (ACTH) in Captive Northern Fur Seals, Callorhinus ursinus

The effect of adrenocorticotrophic hormone (ACTH) on circulating hormones and leukocytes were examined in six adult (2M, 4F) northern fur seals, Callorhinus ursinus. A control study using physiological saline was carried out on two of the female fur seals. Blood samples were taken prior to injection, and at 8 time periods following i.m. injection with saline or 10-28 IU ACTH (0.215-0.306 IU/kg). Stimulation by ACTH caused an elevation of both cortisol and aldosterone levels, along with an increase in neutrophile and a decrease in lymphocytes and eosinophils. Peak times for cortisol were within 3h after stimulation and aldosterone peaked within 1.5h. In contrast to the characteristic response to ACTH by terrestrial mammals, aldosterone peaks were relatively greater than cortisol peaks, a pattern similar found in studies of other marine mammals. The results of this study suggest a common adaptation in the stress response of marine mammals

Oceanic Heat Content Variability in the Eastern Pacific Ocean for Hurricane Intensity Forecasting

Recent evidence supports the premise that the subsurface ocean structure plays an important role in modulating air–sea fluxes during hurricane passage, which in turn, affects intensity change. Given the generally sparse in situ data, it has been difficult to provide region-to-basin-wide estimates of isotherm depths and upper-ocean heat content (OHC). In this broader context, satellite-derived sea surface height anomalies (SSHAs) from multiple platforms carrying radar altimeters are blended, objectively analyzed, and combined with a hurricane-season climatology to estimate isotherm depths and OHC within the context of a reduced gravity model at 0.25° spatial intervals in the eastern Pacific Ocean where tropical cyclone intensity change occurs. Measurements from the Eastern Pacific Investigation of Climate in 2001, long-term tropical ocean atmosphere mooring network, and volunteer observing ship deploying expendable bathythermograph (XBT) profilers are used to carefully evaluate satellite-based measurements of upper-ocean variability. Regression statistics reveal small biases with slopes of 0.8–0.9 between the subsurface measurements compared with isotherm depths (20° and 26°C), and OHC fields derived from objectively analyzed SSHA field. Root-mean-square differences in OHC range between 10 and 15 kJ cm−2 or roughly 10%–15% of the mean signals. Similar values are found for isotherm depth differences between in situ and inferred satellite-derived values. Blended daily values are used in the Statistical Hurricane Intensity Prediction Scheme (SHIPS) forecasts as are OHC estimates for the Atlantic Ocean basin. An equivalent OHC variable is introduced that incorporates the strength of the thermocline at the base of the oceanic mixed layer using a climatological stratification parameter /No, which seems better correlated to hurricane intensity change than just anomalies as observed in Hurricane Juliette in 2001

Oceanic Heat Content Variability in Eastern Pacific Ocean

During the Eastern Pacific Investigation of Climate (EPIC) in September 2001 sponsored by NSF and NOAA, oceanic current, temperature and salinity profiles were acquired by deploying airborne expendable profilers from research aircraft flights above the warm pool and along the 95oW transect. Based on in situ measurements, an anticyclonic warm eddy was forced by a low-level atmospheric jet over the Gulf of Papagayo earlier in the year. Sequential images from satellite altimetry over a several month interval suggest that the eddy propagated west to southwest at a speed of 13-15 cm s-1 consistent with a Rossby wave. A second aspect of the Eastern Pacific Ocean is the shoaling thermocline to form the Costa Rica Dome. This warm eddy propagated over the warm pool and had a pronounced impact on the isotherm depths and on oceanic heat content (OHC) variability.Using monthly and seasonal oceanic climatologies, satellite-derived estimates of OHC are compared to those from in situ profiler data as well as TAO mooring measurements in the Eastern Pacific Ocean during EPIC. While OHC values are much less (50 KJ cm-2) than in the western Atlantic Ocean basins (>100 KJ cm-2), in situ data exhibits more structure in the upper 100 m where observed buoyancy frequencies across the oceanic mixed layer (OML) base are nearly twice as large as those in the Atlantic Ocean basin. These spatial variations have implications for the OML (and OHC) budgets and through shear-induced mixing processes and feedback to the atmosphere (i.e. hurricane Juliette). If models relax back to climatology, temperature and salinity structures will not support realistic density and buoyancy structure, leading to poor predictions of the OML responses that feedback to the atmosphere during strong wind events such as gap winds and hurricanes

Observed air-sea interactions in tropical cyclone Isaac over Loop Current mesoscale eddy features

•Rare direct observations of coupled air-sea interactions during the intensification of a tropical cyclone over Gulf of Mexico’s warm oceanic mesoscale eddy features.•New evidence supporting the hypothesis that enhanced buoyant forcing from the ocean is an important intensification mechanism in tropical cyclones over warm oceanic mesoscale eddy features.•First direct observations of a positive oceanic feedback mechanism on storm intensity via wind-driven horizontal convergence of warm sea surface temperatures over warm oceanic mesoscale eddy features.•New direct measurements of contrasting vertical shear, gradient Richardson number, and vertical mixing in Gulf of Mexico’s mesoscale eddy features during the forced stage in a hurricane.•Direct measurements of the water mass response to a Gulf of Mexico hurricane, including an upper-ocean fresh water anomaly and the formation of a new density class. Air-sea interactions during the intensification of tropical storm Isaac (2012) into a hurricane, over warm oceanic mesoscale eddy features, are investigated using airborne oceanographic and atmospheric profilers. Understanding these complex interactions is critical to correctly evaluating and predicting storm effects on marine and coastal facilities in the Gulf of Mexico, wind-driven mixing and transport of suspended matter throughout the water column, and oceanic feedbacks on storm intensity. Isaac strengthened as it moved over a Loop Current warm-core eddy (WCE) where sea surface warming (positive feedback mechanism) of ∼0.5°C was measured over a 12-h interval. Enhanced bulk enthalpy fluxes were estimated during this intensification stage due to an increase in moisture disequilibrium between the ocean and atmosphere. These results support the hypothesis that enhanced buoyant forcing from the ocean is an important intensification mechanism in tropical cyclones over warm oceanic mesoscale eddy features. Larger values in equivalent potential temperature (θE=365   ∘K) were measured inside the hurricane boundary layer (HBL) over the WCE, where the vertical shear in horizontal currents (δV) remained stable and the ensuing cooling vertical mixing was negligible; smaller values in θE (355   ∘K) were measured over an oceanic frontal cyclone, where vertical mixing and upper-ocean cooling were more intense due to instability development in δV. Thus, correctly representing oceanic mesoscale eddy features in coupled numerical models is important to accurately reproduce oceanic responses to tropical cyclone forcing, as well as the contrasting thermodynamic forcing of the HBL that often causes storm intensity fluctuations over these warm oceanic regimes

Eastern Pacific Ocean heat content estimates from altimetry for operational hurricane intensity forecasts

As part of a NOAA Joint Hurricane Testbed effort, an Eastern Pacific (EPAC) oceanic heat content (OHC) estimation scheme was developed for use in the Statistical Hurricane Intensity Prediction Scheme for predicting hurricane intensity. The approach follows those made operational for hurricane intensity forecasts from SHIPS in the Atlantic Ocean Basin. In the EPAC, the modified algorithm computes OHC from multiple platform radar altimeters and sea surface temperatures from TRMM microwave imager. Altimeter data are smoothed, combined and objectively analyzed to a 0.5o grid to estimate isotherm depths and OHC variations based on a seasonal climatology. Estimates from 2000 to 2006 were compared to several sets of thermal structure measurements from NOAA's Tropical Atmosphere Ocean (TAO) buoys. Within the context of a two-layer fluid, satellite-derived estimates were in good agreement with the in situ data. Regression analyses revealed RMS differences of a few meters in isotherm depths and OHC estimates of less than 8 KJ cm-2

Development and Assessment of the Systematically Merged Pacific Ocean Regional Temperature and Salinity (SPORTS) Climatology for Ocean Heat Content Estimations

Abstract A Systematically Merged Pacific Ocean Regional Temperature and Salinity (SPORTS) climatology was created to estimate ocean heat content (OHC) for tropical cyclone (TC) intensity forecasting and other applications. A technique similar to the creation of the Systematically Merged Atlantic Regional Temperature and Salinity (SMARTS) climatology was used to blend temperature and salinity fields from the Generalized Digital Environment Model and World Ocean Atlas 2001 at a 0.25° resolution. The weights for the blending of these two climatologies were estimated by minimizing residual covariances across the basin. Drift velocities associated with eddy variability were accounted for using a series of 3-yr sea surface height anomalies (SSHA) to ensure continuity between the periods of different altimeters. In addition to producing daily estimates of the 20° and 26°C isotherm depths, mixed-layer depth, and OHC, the model produces mapping errors from the optimal interpolation of the SSHA due to gaps in altimeter track coverage and sensor uncertainties. Using SPORTS with satellite-derived sea surface temperature (SST) and SSHA fields from radar altimetry, daily OHC was estimated from 2000 to 2011 using a 2.5-layer model approach. Argo profiling floats, expendable probes from ships and aircraft, long-term Tropical Atmosphere Ocean (TAO) moorings, and drifters provide more than 267 000 quality controlled in situ thermal profiles to assess uncertainty in estimates from SPORTS. This carefully constructed climatology creates an accurate estimation of OHC from satellite-based measurements, which can then be used in TC intensity forecasts in the North Pacific Ocean and analysis of ocean thermodynamics. The SPORTS time and space series extends from 1998 to 2016, forming a 19-yr dataset by the end of 2016

Observed ocean thermal response to H

The 2008 Atlantic hurricane season featured two hurricanes, Gustav and Ike, crossing the Gulf of Mexico (GOM) within a 2 week period. Over 400 airborne expendable bathythermographs (AXBTs) were deployed in a GOM field campaign before, during, and after the passage of Gustav and Ike to measure the evolving upper ocean thermal structure. AXBT and drifter deployments specifically targeted the Loop Current (LC) complex, which was undergoing an eddy‐shedding event during the field campaign. Hurricane Gustav forced a 50 m deepening of the ocean mixed layer (OML), dramatically altering the prestorm ocean conditions for Hurricane Ike. Wind‐forced entrainment of colder thermocline water into the OML caused sea surface temperatures to cool by over 5°C in GOM common water, but only 1–2°C in the LC complex. Ekman pumping and a near‐inertial wake were identified by fluctuations in the 20°C isotherm field observed by AXBTs and drifters following Hurricane Ike. Satellite estimates of the 20° and 26°C isotherm depths and ocean heat content were derived using a two‐layer model driven by sea surface height anomalies. Generally, the satellite estimates correctly characterized prestorm conditions, but the two‐layer model inherently could not resolve wind‐forced mixing of the OML. This study highlights the importance of a coordinated satellite and in situ measurement strategy to accurately characterize the ocean state before, during, and after hurricane passage, particularly in the case of two consecutive storms traveling through the same domain. Key Points: Ocean response to two hurricanes were observed during a 2008 field campaign Satellite methods accurately measured prestorm ocean heat content The near‐inertial response could not be captured by the two‐layer mode

Can ocean community production and respiration be determined by measuring high-frequency oxygen profiles from autonomous floats?

Oceanic primary production forms the basis of the marine food web and provides a pathway for carbon sequestration. Despite its importance, spatial and temporal variations of primary production are poorly observed, in large part because the traditional measurement techniques are laborious and require the presence of a ship. More efficient methods are emerging that take advantage of miniaturized sensors integrated into autonomous platforms such as gliders and profiling floats. One such method relies on determining the diurnal cycle of dissolved oxygen in the mixed layer and has been applied successfully to measurements from gliders and mixed-layer floats. This study is the first documented attempt to estimate primary production from diurnal oxygen changes measured by Argo-type profiling floats, thus accounting for the whole euphotic zone. We first present a novel method for correcting measurement errors that result from the relatively slow response time of the oxygen optode sensor. This correction relies on an in situ determination of the sensor's effective response time. The method is conceptually straightforward and requires only two minor adjustments in current Argo data transmission protocols: (1) transmission of measurement time stamps and (2) occasional transmission of downcasts in addition to upcasts. Next, we present oxygen profiles collected by 10 profiling floats in the northern Gulf of Mexico, evaluate whether community production and respiration can be detected, and show evidence of internal oscillations influencing the diurnal oxygen signal. Our results show that profiling floats are capable of measuring diurnal oxygen variations although the confounding influence of physical processes does not permit a reliable estimation of biological rates in our dataset. We offer suggestions for recognizing and removing the confounding signals

Coastal ocean surface current response to hurricane Jeanne detected by WERA

In September 04, hurricane Jeanne made landfall in South Florida as a category 2 storm. During this period, Jeanne excited an energetic coastal current response as measured by a dual station Wellen Radar (WERA) deployed as part of the ONR-sponsored Southeast Atlantic Coastal Ocean Observing System. An eastward current response of 1 m s-1 emanated from the Biscayne Bay where offshore surface winds approached 25 m s-1. This current response forced an eastward bulge of ≈ 100 km2 resulting in an offshore Florida Current meander. Given fetch-limited conditions and the fact that the measurements were acquired along the southern side of Jeanne, these data suggest that WERA can certainly remain operational for winds up to 25 m s-1, and perhaps even larger if the array sites can be hardened to withstand higher winds. Using the evolution of the forced surface currents and winds at Fowey Rocks, the surface drag coefficient is estimated from the forced shallow water equations. These high-resolution surface current measurements provide an approach to infer the wind stress input under hurricane conditions