Remote Sensing of Particulate Organic Carbon Pools in the High-Latitude Oceans

The general goal of this project was to characterize spatial distributions at basin scales and variability on monthly to interannual timescales of particulate organic carbon (POC) in the high-latitude oceans. The primary objectives were: (1) To collect in situ data in the north polar waters of the Atlantic and in the Southern Ocean, necessary for the derivation of POC ocean color algorithms for these regions. (2) To derive regional POC algorithms and refine existing regional chlorophyll (Chl) algorithms, to develop understanding of processes that control bio-optical relationships underlying ocean color algorithms for POC and Chl, and to explain bio-optical differentiation between the examined polar regions and within the regions. (3) To determine basin-scale spatial patterns and temporal variability on monthly to interannual scales in satellite-derived estimates of POC and Chl pools in the investigated regions for the period of time covered by SeaWiFS and MODIS missions

Phytoplankton bloom and the vertical thermal structure of the upper ocean

Local heating rate within the oceanic mixed layer (ML) depends not only on the amount of solar radiation incident on the sea surface, but also on the vertical distribution of the irradiance in the water column. We have evaluated the effect of a phytoplankton bloom on mixed layer depth and temperature at a high latitude site near Iceland. The level 2½ version of the Mellor-Yamada (1982) turbulence scheme has been modified to include the vertical distribution of irradiance. This has allowed the investigation of the ML temperature and stability structure resulting from both physical and biological effects. An important part of the model is the parameterization of pigment-dependence which affects the spectral attenuation coefficient for downwelling irradiance as proposed by Morel (1988). Concurrent, high temporal resolution time series of physical and bio-optical data were used for the model. These data were acquired using a mooring deployed during the spring of 1989. We have estimated that the increase of phytoplankton abundance induced an increase of the sea surface temperature by about 0.2°C at the mooring site. This led to stronger near-surface thermal stratification and shallower mixed layers. The dependence of the upper layer thermal structure on biology is more important when vertical mixing is weaker and when phytoplankton concentrations are higher

Phytoplankton bloom phenomena in the North Atlantic Ocean and Arabian Sea

Author Posting. © The Author(s), 2014. This is the author's version of the work. It is posted here by permission of International Council for the Exploration of the Sea for personal use, not for redistribution. The definitive version was published in ICES Journal of Marine Science 72 (2015): 2021-2028, doi:10.1093/icesjms/fsu241.We review bio-optical and physical data from three mooring experiments, the Marine Light–Mixed Layers programme in spring 1989 and 1991 in the Iceland Basin (59°N/21°W), and the Forced Upper Ocean Dynamics Experiment in the central Arabian Sea from October 1994 to 1995 (15.5°N/61.5°E). In the Iceland Basin, from mid-April to mid-June in 1989, chlorophyll-a concentrations are sensitive to small changes in stratification, with intermittent increases early in the record. The spring increase occurs after 20 May, coincident with persistent water column stratification. In 1991, the bloom occurs 2 weeks earlier than in 1989, with a background of strong short-term and diurnal variability in mixed layer depth and minimal horizontal advection. In the Arabian Sea, the mixing response to the northeast and southwest monsoons, plus the response to mesoscale eddies, produces four blooms over the annual cycle. The mixed layer depth in the Arabian Sea never exceeds the euphotic zone, allowing interactions between phytoplankton and grazer populations to become important. For all three mooring experiments, change in water column stratification is key in producing phytoplankton blooms.2016-01-0

Comparison of in situ and satellite ocean color determinations of particulate organic carbon concentration in the global ocean

Ocean color satellite missions have provided more than 16-years of consistent, synoptic observations of global ocean ecosystems. Surface chlorophyll concentrations (Chl) derived from satellites have been traditionally used as a metric for phytoplankton biomass. In recent years interpretation of ocean-color satellite data has progressed beyond the estimation of Chl. One of the newer ocean color products is particulate organic carbon (POC) concentration. In this paper we carry out comparisons of simultaneous satellite and in situ POC determinations. Our results indicate that the performance of the standard NASA POC algorithm (Stramski et al., 2008) is comparable to the standard empirical band ratio algorithms for Chl

Spatial and temporal variability of sea surface temperature in the Baltic Sea based on 32-years (1982–2013) of satellite data

Satellite measurements provide synoptic view of sea surface temperature (SST) and can be used to trace global and regional climate trends. In this study we have examined the multiyear trends and variability of the Baltic Sea SST using 32-years (1982–2013) of satellite data. Our results indicate that there is a statistically significant trend of increasing SST in the entire Baltic Sea, with values ranging from 0.03 to 0.06°C year−1, depending on the location. SSTs averaged over the entire Baltic Sea increase at the rate of 0.05°C year−1. Higher values of SST trend are generally present in the summer months, while trend is not statistically significant in the winter months. The seasonal cycle of SST in the Baltic Sea is characterized by well-defined winter and summer seasons. The average amplitude (16–18°C) of this cycle is significantly larger than in the North Sea waters located at the same latitudes as the Baltic Sea. The analyzed data set also highlights considerable interannual SST variability, which is coherent in different regions of the Baltic Sea and significantly correlated with interannual variability of the air temperature. SST variability in the Baltic Sea in winter can be linked to the North Atlantic Oscillation index

Surface currents in the Porsanger fjord in northern Norway

We describe surface currents in the Porsanger fjord (Porsangerfjorden) located in the European Arctic in the vicinity of the Barents Sea. Our analysis is based on surface current data collected in the summer of 2014 using High Frequency (WERA, Helzel Messtechnik GmbH) radar system. One of our objectives was to separate out the tidal from the nontidal components of the currents and to determine the most important tidal constituents. Tides in the Porsanger fjord are substantial, with tidal range on the order of about 3 m. Tidal analysis attributes to tides about 99% of variance in sea level time series recorded in Honningsvaag. The most important tidal component in sea level data is the M2 component, with amplitude of ~90 cm. The S2 and N2 constituents (amplitude of ~20 cm) also play a significant role in the semidiurnal sea level oscillations. The most important diurnal component is K1 with amplitude of about 8 cm. The most important tidal component in analyzed surface currents records is the M2 component. The second most important component is the S2. Our results indicate that in contrast to sea level, only about 10-30% of variance in surface currents can be attributed to tidal currents. This means that about 70-90% of variance is due to wind-induced and geostrophic currents

The vertical structure of the upper ocean during the Marine Light - Mixed Layer Experiment

The Marine Light--Mixed Layer (MLML) program was predicated on the concept that temporal and spatial variability in the marine ecosystem would be best understood in the context of physical processes. The MLML experiment took place in the sub-Arctic North Atlantic ocean, approximately 275 miles south of Reykjavik, Iceland from 30 April to 6 September 1991. The field program included a central surface mooring to document the temporal evolution of physical, biological and optical properties. In this paper we investigated physical processes by describing the vertical structure of temperature and velocity in the upper 300 m of the water column and their changes in response to heat and momentum fluxes at the sea surface. The deployment period included the spring transition, where upper ocean restratification was initiated after deep winter mixing, and the fall transition, where mixed layer deepening began again. The dominant signal in both temperature and velocity was seasonal variation. Com..