Time series of black carbon aerosol measurements from Neumayer Station, 1999-2011

Continuous black carbon (BC) observations were conducted from 1999 through 2009 by an Aethalometer (AE10) and from 2006 through 2011 by a Multi-Angle Absorption Photometer (MAAP) at Neumayer Station (NM) under stringent contamination control. Considering the respective observation period, BC concentrations measured by the MAAP were somewhat higher (median ± standard deviation: 2.1 ± 2.0 ng/m**3) compared to the AE10 results (1.6 ± 2.1 ng/m**3). Neither for the AE10 nor for the MAAP data set a significant long-term trend could be detected. Consistently a pronounced seasonality was observed with both instruments showing a primary annual maximum between October and November and a minimum in April with a maximum/minimum ratio of 4.5/1.6 = 3.8 and 2.7/0.64 = 4.2 for the MAAP and AE10 data, respectively. Occasionally a secondary summer maximum in January/February was visible. With the aim to assess the impact of BC on optical properties of the aerosol at NM, we evaluated the BC data along with particle scattering coefficients measured by an integrating nephelometer. We found the mean single scattering albedo of w550 = 0.992 ± 0.0090 (median: 0.994) at a wavelength of 550 nm with a range of values from 0.95 to 1.0.

Absorption coefficients of particulate matter and chlorophyll a concentrations at time series station OLIPAC

Spectral absorption coefficients of total particulate matter ap (lambda) were determined using the in vitro filter technique. The present analysis deals with a set of 1166 spectra, determined in various oceanic (case 1) waters, with field chl a concentrations ([chl]) spanning 3 orders of magnitude (0.02-25 mg/m**3). As previously shown [Bricaud et al., 1995, doi:10.1029/95JC00463] for the absorption coefficients of living phytoplankton a phi (lamda), the ap (labda) coefficients also increase nonlinearly with [chl]. The relationships (power laws) that link ap (lambda) and a phi (lambda) to [chl] show striking similarities. Despite large fluctuations, the relative contribution of nonalgal particles to total absorption oscillates around an average value of 25-30% throughout the [chl] range. The spectral dependence of absorption by these nonalgal particles follows an exponential increase toward short wavelengths, with a weakly variable slope (0.011 ± 0.0025/nm). The empirical relationships linking ap (lambda) to ([chl]) can be used in bio-optical models. This parameterization based on in vitro measurements leads to a good agreement with a former modeling of the diffuse attenuation coefficient based on in situ measurements. This agreement is worth noting as independent methods and data sets are compared. It is stressed that for a given ([chl]), the ap (lambda) coefficients show large residual variability around the regression lines (for instance, by a factor of 3 at 440 nm). The consequences of such a variability, when predicting or interpreting the diffuse reflectance of the ocean, are examined, according to whether or not these variations in ap are associated with concomitant variations in particle scattering. In most situations the deviations in ap actually are not compensated by those in particle scattering, so that the amplitude of reflectance is affected by these variations.

Mesopelagic fish abundance and particle size spectrum analysis from Maria S. Merian cruise MSM26, spring 2013

One of the goals of EU BASIN is to understand variability in production across the Atlantic and the impact of this variability on higher trophic levels. One aspect of these investigations is to examine the biomes defined by Longhurst (2007). These biomes are largely based on productivity measured with remote sensing. During MSM 26, mesopelagic fish and size-spectrum data were collected to test the biome classifications of the north Atlantic. In most marine systems, the size-spectrum is a decay function with more, smaller organisms and fewer larger organisms. The intercept of the size-spectrum has been linked to overall productivity while the slope represents the "rate of decay" of this productivity (Zhou 2006, doi:10.1093/plankt/fbi119). A Laser In-Situ Scattering Transmissometer was used to collect size-spectrum data and net collections were made to capture mesopelagic fish. The relationship among the mesopelagic fish size and abundance distributions will be compared to the estimates of production from the size-spectrum data to evaluate the biomes of the stations occupied during MSM 26.

Particle size spectrum analysis during Maria S. Merian cruise MSM26, spring 2013

A Laser In-Situ Scattering Transmissometer (LISST) was used to collect vertical distribution data of particles from 2.5 to 500 µm in size. The LISST uses a multi-ring detector to measure scattering light of particles from a laser diode. Particles are classified into 32 log-spaced bins and the concentration of each bin is calculated as micro-liters per liter (µl/l). The instrument is rated to a depth of 300 m, and also records temperature and pressure. The sample interval was set to record every second. The LISST was attached to the LOPC frame to conduct casts and allow for particle-size comparisons between the two instruments. The LOPC is rated to a depth of 2000 m, thus a short deployment to a depth of 300 m was first conducted with both instruments. The instruments were then returned to the deck and the LISST removed via a quick release bracket so deep LOPC casts could be continued at a station. Raw LISST size-spectrum data is presented as concentrations for each of the 32 size bins for every second of the cast.