Never before have oceanopgraphers and climate scientists had such comprehensive
subsurface ocean data. The number of publications based on Argo is growing rapidly and the range of applications is enormous.
The following examples show some applications of data from Argo (and from other profiling
floats that are still in the experimental stages). They are drawn from the published
literature
and give a foretaste of the impact that Argo will have.
Environmental assessment in the Gulf of Alaska
Freeland, H.J. and P.F.Cummins, 2005: Argo: A new tool for environmental monitoring and assessment of the world’s ocean, an example from the NE Pacific. Progress in Oceanography, 64(1), 31-44.
Abstract
Argo is an international project that is deploying profiling drifters in all of the oceans of the world, with the exception of the Arctic Ocean. Though still in its implementation phase the Argo array is now supplying an impressive amount of data which offers new opportunities to assess and monitor the environmental status of many regions of the world oceans. Recently, changes in the Gulf of Alaska have been documented by other means that suggest large changes in the T/S relationships and related changes in nutrient supply and productivity. This paper examines these unusual changes to demonstrate the use of the Argo database to determine the physical status of an ecosystem. While the methods of analysis are general, they are here specifically applied to the N.E. Pacific Ocean. We show how it is possible to monitor the baroclinic geostrophic circulation fields in near real-time and correlate these changes with alterations in the stratification of the upper water column.
The stratification of the upper ocean, computed as a sigma- t difference between 75 dbar and the surface, at Ocean Station Papa. The blue line is a time series of stratification derived from Argo floats, the red points and the bars are expected differences and 95% confidence bounds.
Oxygen measurements from profiling floats
Körtzinger, Arne, Jens Schimanski and Uwe Send, 2005: High Quality Oxygen Measurements from Profiling Floats: A Promising New Technique. Journal of Atmospheric and Oceanic Technology 22(3), 302–308.
Abstract
Two state-of-the-art profiling floats were equipped with novel optode-based oceanographic oxygen sensors. Both floats were simultaneously deployed in the central Labrador Sea gyre on 7 September 2003. They drift at a depth of 800 db and perform weekly profiles of temperature, salinity, and oxygen in the upper 2000 m of the water column. The initial results from the first 6 months of operation are presented. Data are compared with a small hydrographic oxygen survey of the deployment site. They are further examined for measurement quality, including precision, accuracy, and drift aspects. The first 28 profiles obtained are of high quality and show no detectable sensor drift. A method of long-term drift control is described and a few suggestions for the operation protocol are provided.
|
|
Left "Calibration" of the first three oxygen profiles from both floats with Winkler oxygen data from discrete samples taken at nearby hydrocasts. The procedure removes the offset due to an inadequate factory calibration of the early sensors. Right First 28 calibrated profiles of (left panel) oxygen and (right panel) oxygen saturation obtained in the Labrador Sea illustrating quality and resolution as well as utility of this new approach for oxygen measurements in the ocean.
Indonesian throughflow in the
Indian Ocean
Phillips, Helen E., Susan E. Wijffels and Ming Feng, 2005: Interannual variability in the freshwater content of the Indonesian-Australian Basin. Geophys. Res. Lett., 32(3), L03603, doi:10.1029/2004GL021755,2005
Abstract
An average freshening of 0.2 psu, extending from 100°E to Australia, 25°S to Indonesia and down to 180 m depth, persisted for more than 3 years from 1999 to 2002. We map the anomaly using CTD profiles from Argo floats and suggest that the dominant forcing for the anomaly is surface freshwater flux over the Indonesian seas that is advected into the region. Using historical CTD data and surface freshwater flux reanalysis products we show that the Indonesian Australian Basin experiences strong interannual variability in upper ocean freshwater content and that the recent fresh event, a result of a long-lasting La Niña, is unprecedented during the last 25 years.
Salinity anomalies relative to CARS climatology during 1995 from WOCE CTDs, during the fresh event of 1999–2002 from Argo, and after the fresh event during 2003 and 2004 from Argo. Upper panels. Geographic distribution of anomalies on Theta = 22 C. Lower panels. Mean meridional section of zonally averaged salinity anomalies during the four periods. Contours are climatological salinity along 110 E. Middle panel. Mean sea surface salinity as a function of latitude from thermosalinograph for the fresh period (courtesy of T. Delcroix, IRD, France, personal communication).
Ocean data assimilation
Guinehut, S., P-Y. Le Traon, G. Larnicol and S. Philipps S, 2004: Combining Argo and remote-sensing data to estimate the ocean three dimensional temperature fields - a first approach based on simulated observations. Journal of Marine Systems. 46(1-4),85-98
Abstract
The study aims to analyze the contribution of the combination of high-resolution sea level and sea surface temperature satellite data with accurate but sparse in situ temperature profile data as given by Argo to the reconstruction of the large-scale, monthly mean, 200-m depth temperature fields. The main issue is to reconstruct instantaneous temperature fields at high temporal and spatial resolution and thus improve the representation of the large-scale and low-frequency temperature fields at the given depth. The method is developed and presented for the temperature field at 200-m depth but can be applied to any depth and also to the salinity field. The study uses outputs and profiling float simulations derived from a state-of-the-art, eddy-resolving (1/6°-resolution) primitive equation model of the North Atlantic. Synthetic 200-m temperatures are first derived from simulated altimeter and SST data through a multiple linear regression; they are then combined with individual Argo 200-m simulated temperatures. The optimal merging uses an objective analysis method that takes into account analyzed errors on the observations and, particularly, correlated errors on synthetic temperatures deduced from remote-sensing data. Results indicate that the optimal combination is instrumental in reducing the aliasing due to the mesoscale variability and in adjusting the high-resolution combined fields to the in situ data. The rms of mapping error of the large-scale and low-frequency temperature fields at 200-m depth is largely reduced (by a factor of 4 in large mesoscale variability regions) when combining both data types, as compared to the results obtained using only in situ profiles.
Two-hundred-meter T anomalies time series (as monthly means) (A) in the NBC retroflection, (B) in the Gulf Stream region and (C) in the Subtropical gyre from the model large-scale and low-frequency reference fields, the Argo-like experiment and the optimal merging experiment.
Subsurface velocity mapping
Park, Y.-G., Oh, K.-H., Chang, K.-I., Suk, M.-S., 2004. Intermediate level circulation of the southwestern part of the East/Japan Sea estimated from autonomous isobaric profiling floats, Geophys. Res. Lett., 31, L13213, doi:10.1029/2004GL020424
Abstract
With trajectory data from autonomous isobaric profiling floats (PALACE, APEX and PROVOR), we obtained a detailed intermediate level circulation pattern over the southwestern part of the East/Japan Sea. The circulation pattern, which is consistent with moored current meter data obtained at a few locations, is largely controlled by the bottom topography. The main features we have found are as follows: 1) a cyclonic circulation along the Korean coast and the continental break around the Ulleung Basin and the western side of Oki Spur to the Yamato Rise, and 2) a cold current from the Japan Basin to the Ulleung Basin through the Ulleung Interplain Gap, which is a part of the anticyclonic flow over the Korea Plateau, a Taylor column
|
|
Left: Velocity estimates at the parking depths using 1381 displacement data from 24 floats. Different color means different parking depth. Right A schematic of intermediate level circulation pattern inferred from the float data over the southwestern part of the East/Japan Sea.
Coriolis project has decided to support research activities that were related either to data collection, or quality control or also generation of value added product such as climatology. About 10 projects per year are partially funded by Coriolis and details about work progress can be found on Coriolis WWW site.