Perspectives and Integration in SOLAS Science

Why a chapter on Perspectives and Integration in SOLAS Science in this book? SOLAS science by its nature deals with interactions that occur: across a wide spectrum of time and space scales, involve gases and particles, between the ocean and the atmosphere, across many disciplines including chemistry, biology, optics, physics, mathematics, computing, socio-economics and consequently interactions between many different scientists and across scientific generations. This chapter provides a guide through the remarkable diversity of cross-cutting approaches and tools in the gigantic puzzle of the SOLAS realm. Here we overview the existing prime components of atmospheric and oceanic observing systems, with the acquisition of ocean–atmosphere observables either from in situ or from satellites, the rich hierarchy of models to test our knowledge of Earth System functioning, and the tremendous efforts accomplished over the last decade within the COST Action 735 and SOLAS Integration project frameworks to understand, as best we can, the current physical and biogeochemical state of the atmosphere and ocean commons. A few SOLAS integrative studies illustrate the full meaning of interactions, paving the way for even tighter connections between thematic fields. Ultimately, SOLAS research will also develop with an enhanced consideration of societal demand while preserving fundamental research coherency. The exchange of energy, gases and particles across the air-sea interface is controlled by a variety of biological, chemical and physical processes that operate across broad spatial and temporal scales. These processes influence the composition, biogeochemical and chemical properties of both the oceanic and atmospheric boundary layers and ultimately shape the Earth system response to climate and environmental change, as detailed in the previous four chapters. In this cross-cutting chapter we present some of the SOLAS achievements over the last decade in terms of integration, upscaling observational information from process-oriented studies and expeditionary research with key tools such as remote sensing and modelling. Here we do not pretend to encompass the entire legacy of SOLAS efforts but rather offer a selective view of some of the major integrative SOLAS studies that combined available pieces of the immense jigsaw puzzle. These include, for instance, COST efforts to build up global climatologies of SOLAS relevant parameters such as dimethyl sulphide, interconnection between volcanic ash and ecosystem response in the eastern subarctic North Pacific, optimal strategy to derive basin-scale CO2 uptake with good precision, or significant reduction of the uncertainties in sea-salt aerosol source functions. Predicting the future trajectory of Earth’s climate and habitability is the main task ahead. Some possible routes for the SOLAS scientific community to reach this overarching goal conclude the chapter

Spectral effects of atmospheric dust and clouds on estimation of chlorophyll-aconcentration from radiation measurements

Atmospheric dust and clouds modify the spectral distribution of the incident solar radiation. The influence of these spectral effects on the determination of chlorophyll-a concentration from the sea surface and remotely sensed radiation measurements made from ships, aircrafts or satellites was studied in the region off Northwest Africa in the Atlantic Ocean. The chlorophyll-a algorithms that are typically used in ocean colour community are based on ratios of reflectance values of different wavelengths. This fact, together with the wavelength dependent effect of atmospheric dust and clouds, causes uncertainties in the estimation of chlorophyll-a concentration. The most frequently used Morel, OC4v4 and OC3M chlorophyll-a algorithms were included in the investigation. The highest and the smallest uncertainties were found for the Morel and the OC3M algorithms, respectively. For the first time, sky conditions with dust and clouds together in the atmosphere were studied. Overestimations of the chlorophyll-a concentration of up to 8.8% were observed in the case of dusty skies without clouds. The concentration was also overestimated between 7.6% and 14.3% for skies with mixtures of dust and clouds increasing the solar irradiance. Underestimations of up to 24.1% and overestimations of up to 12.2% were found for skies with mixtures of dust and clouds decreasing the solar irradiance. Compensations of the influences of spectral effects were observed at special ratios of clouds to dust. Earlier results in relation to the impact of clouds on the estimation of chlorophyll-a concentration were verified. The spectral effects of cloudy skies cannot be neglected because it may result in an error of up to 40% of the estimated value

Sulfur plume sizes and ENSO indices between 2002-2013 at Callao and Pisco, coastal Peru

For the first time, the impact of the El Niño‐Southern Oscillation (ENSO) on the surface sulfur plumes off the Peruvian upwelling system has been studied. The investigations demonstrated a strong correlation between the ENSO and the sulfur plumes in the coastal areas of Callao and Pisco. During the El Niño phases, the sulfur plumes disappeared almost completely because of equatorial remotely forced oxygenation episodes. The La Niña events were associated with strong oxygen deficiency over the Peruvian shelf, supporting the formation of hydrogen sulfide and, consequently, the occurrence of sulfur plumes. This impact was smaller at Callao, because the La Niña phases in this coastal area were interrupted by weak oxygenation events. During the neutral phases, oxygen‐poor waters were also present in the Peruvian shelf areas, promoting the large size of sulfur plumes. However, they were not forced by the remotely driven processes resulting from ENSO phenomena

Area-averaged mean seasonal cycles of chlorophyll-a concentration, sea surface temperature, alongshore wind stress, westward wind speed and dust component of the aerosol optical depth at 550 nm

Nutrient supply in the area off Northwest Africa is mainly regulated by two processes, coastal upwelling and deposition of Saharan dust. In the present study, both processes were analyzed and evaluated by different methods, including cross-correlation, multiple correlation, and event statistics, using remotely sensed proxies of the period from 2000 to 2008 to investigate their influence on the marine environment. The remotely sensed chlorophyll-a concentration was used as a proxy for the phytoplankton biomass stimulated by nutrient supply into the euphotic zone from deeper water layers and from the atmosphere. Satellite-derived alongshore wind stress and sea-surface temperature were applied as proxies for the strength and reflection of coastal upwelling processes. The westward wind and the dust component of the aerosol optical depth describe the transport direction of atmospheric dust and the atmospheric dust column load. Alongshore wind stress and induced upwelling processes were most significantly responsible for the surface chlorophyll-a variability, accounting for about 24% of the total variance, mainly in the winter and spring due to the strong north-easterly trade winds. The remotely sensed proxies allowed determination of time lags between biological response and its forcing processes. A delay of up to 16 days in the surface chlorophyll-a concentration due to the alongshore wind stress was determined in the northern winter and spring. Although input of atmospheric iron by dust storms can stimulate new phytoplankton production in the study area, only 5% of the surface chlorophyll-a variability could be ascribed to the dust component in the aerosol optical depth. All strong desert storms were identified by an event statistics in the time period from 2000 to 2008. The 57 strong storms were studied in relation to their biological response. Six events were clearly detected in which an increase of chlorophyll-a was caused by Saharan dust input and not by coastal upwelling processes. Time lags of <8 days, 8 days, and 16 days were determined. An increase in surface chlorophyll-a concentration of up to 2.4 mg m**3 after dust storms in which the dust component of the aerosol optical depth was up to 0.9 was observed

Seasonal cycles of monthly means of ground truth wind speed of METAR station GVAC and of area-averaged TMI wind speed at 37 GHz for the Cape Verde Island Sal

In the present paper ground truth and remotely sensed datasets were used for the investigation and quantification of the impact of Saharan dust on microwave propagation, the verification of theoretical results, and the validation of wind speeds determined by satellite microwave sensors. The influence of atmospheric dust was verified in two different study areas by investigations of single dust storms, wind statistics, wind speed scatter plots divided by the strength of Saharan dust storms, and wind speed differences in dependence of microwave frequencies and dust component of aerosol optical depth. An increase of the deviations of satellite wind speeds to ground truth wind speeds with higher microwave frequencies, with stronger dust storms, and with higher amount of coarse dust aerosols in coastal regions was obtained. Strong Saharan dust storms in coastal areas caused mean relative errors in the determination of wind speed by satellite microwave sensors of 16.3% at 10.7 GHz and of 20.3% at 37 GHz. The mean relative errors were smaller in the open sea area with 3.7% at 10.7 GHz and with 11.9% at 37 GHz

Impacts of Saharan dust on downward irradiance and photosynthetically available radiation in the water column

A semi-empirical approach was used to quantify the modification of the underwater light field in amplitude (magnitude effect) and spectral distribution (spectral effect) by different atmospheric conditions altering the incident light. The approach based on an optical model in connection with radiation measurements in the area off Northwest Africa. Key inputs of the model were parameterized magnitude and spectral effects. Various atmospheric conditions were considered: clear sky, dusty sky without clouds, cloudy sky without dust and skies with different ratios of dust and clouds. Their impacts were investigated concerning the modification of the downward irradiance and photosynthetically available radiation in the water column. The impact on downward irradiance depended on the wavelength, the water depth, the optical water properties, the dust and cloud properties, and the ratio of clouds to dust. The influence of clouds on the amplitude can be much higher than that of dust. Saharan dust reduced the photosynthetically available radiation in the water column. Ocean regions were more influenced than coastal areas. Compensations of the magnitude and spectral effects were observed at special water depths in ocean regions and at atmospheric conditions with definite cloud to dust ratio