2 research outputs found
Spatio-Temporal Dynamics Of Phytoplankton Biomass From Ocean Color Remote Sensing And Cmip5 Model Suites
Phytoplankton are the base of the marine food web, and, importantly, drive the biological carbon pump, the combination of photosynthesis, organic carbon sinking and subsurface decomposition of organic matter which effectively sequesters carbon away from the atmosphere. Our knowledge of phytoplankton activity is currently advancing fast through developments of multiple ocean-color remote sensing algorithms and via developments in ecological modules incorporated in climate models. While climate models are projecting relatively clear trends in ocean ecology over the next century, distinguishing between interannual variability and ocean biology trends from satellite observations is difficult. Short record length, satellite data continuity issues and strong interannual variability all impact quantified trends. Additionally, commonly observed chlorophyll-a is not strictly indicative of underlying phytoplankton biomass because of phytoplankton adaptation. This thesis investigates the trends, interannual variability and seasonality in new size-partitioned phytoplankton biomass products, with a focus on the Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) mission period (1997-2010). In Chapter 2 we found phytoplankton biomass increases in the warm ocean regions over this period, opposing common expectations of decreases in warming oceans. Biomass increases are due to increased physical mixing of the watercolumn and are partially attributed to the large scale El Nino Southern Oscillation (ENSO) phenomenon. Recent studies have highlighted the emergence of different types of ENSO, with a shift towards more Central Pacific ENSO events. Chapter 3 uses statistical techniques (agglomerative hierarchical clustering (AHC), empirical orthogonal functional analysis (EOF)) on phytoplankton biomass to characterize ENSO “flavors” in the tropical Pacific. For the first time, we empirically derive biological indices for different ENSO types and show high correlations with existing climate indices. In Chapter 4 we examine in depth seasonal in phytoplankton ecology between the North Eastern Pacific subpolar region and contrast it with North Atlantic subpolar ecology. We discuss drivers of biological changes (iron, nutrients, light, mixing). We reveal large differences between biological variables across ocean-color algorithms, as well as across the latest generation Earth System model suite (Carbon Model Intercomparison Project, CMIP5). Chapter 5 summarizes our findings and future work suggestions. Future work should link surface phytoplankton ecology to ocean-atmosphere carbon fluxes and ocean carbon pump efficiency
Ocean surface provinces off Southwest Iberia based on satellite remote sensing
This thesis aimed to partition the complex surface marine domain off Southwest Iberia
Peninsula (SWIP), using satellite remote sensing, and use it to assess phytoplankton
variability patterns and underlying environmental drivers (1997 – 2015). Three unsupervised
partition strategies, based on distinct input databases and temporal representations, detected a
variable number of partition units (regions, provinces) of singular environmental and
phytoplankton patterns within SWIP. An abiotic-based partition delineated 12 dynamic
Environmental Provinces (EPs) that alternated coverage dominance along the annual cycle.
EP patterns were in general related to phytoplankton biomass, indicated by satellite
chlorophyll-a concentration (Chl-a), and productivity, thus supporting the biological
relevance of this abiotic-based partition. A static partition, based on the main variability
modes of Chl-a, derived 9 Chl-a regions. Moreover, a static partition strategy synthesised
phytoplankton phenological patterns over SWIP into 5 phenoregions, with coherent patterns
of timing, magnitude and duration of blooms. The spatial distribution of EPs, Chl-a regions
and phenoregions shared similarities, which can be considered the main spatial patterns of
SWIP ocean surface. In general, the spatial arrangement of the partition units showed a
separation between coastal and open ocean, a latitudinal division (ca. 36.5oN) over the open
ocean and, over the coast and slope, the influence of coastal upwelling along the west
Portuguese coast and Cape São Vicente, and of river discharge along the northeastern Gulf of
Cadiz. The environmental drivers of phytoplankton varied across partition units. Water
column stratification, riverine discharge and upwelling intensity were the most influential
modulators, and large scale climate indices usually showed minor effects. Environmental
variables, Chl-a and phenology showed significant seasonal variability patterns, varying
across regions. Interannual patterns were more complex, and significant trends were mostly
detected within the Gulf of Cadiz. Linkages between environmental variability and
phytoplankton support their use as an indicator of ecosystem status and change.O oceano superficial é um domínio extremamente complexo e dinâmico, onde as interações
com a atmosfera e o continente modulam a distribuição e atividade dos organismos marinhos
e o clima da Terra. O fitoplâncton, principal produtor primário marinho, é fortemente
influenciado pelos processos atuantes no oceano superficial, constituindo um importante
indicador do estado e variabilidade dos ecossistemas marinhos. Assim, a organização espacial
horizontal do oceano superficial, função da variabilidade das propriedades abióticas e
comunidades biológicas (incluindo o fitoplâncton), apresenta uma série de unidades
funcionais distintas (regiões ou províncias), com atributos e padrões de variabilidade
específicos. A partição ou regionalização do oceano, com identificação e delimitação destas
unidades funcionais, simplifica a complexidade do oceano superficial e representa uma
ferramenta para avaliar e compreender o funcionamento do oceano superficial, apresentando
diversas aplicações ao nível do estudo, gestão e conservação dos ecossistemas marinhos. A
deteção remota por satélite constitui uma fonte valiosa de dados para a partição do oceano
superficial, pois disponibiliza campos sinóticos de várias variáveis oceanográficas e
atmosféricas, em escalas espacial e temporal pertinentes, abrangendo períodos de várias
décadas.
A presente tese pretende particionar o complexo domínio marinho superficial do sudoeste da
Península Ibérica (Southwest Iberia Peninsula, SWIP), com base em deteção remota por
satélite, e avaliar a variabilidade do fitoplâncton e forçadores ambientais associados em
regiões específicas (unidades funcionais) da área de estudo. Para atingir os objectivos
principais foi inicialmente efetuada uma revisão do conhecimento científico sobre as
estratégias de partição do oceano superficial baseadas em deteção remota por satélite
(Capítulo 2) e, posteriormente, foram aplicadas diversas estratégias de partição nãosupervisionadas
à área de estudo (Capítulos 3 - 5). Tais estratégias permitiram particionar a
área de estudo com base em diferentes caraterísticas do oceano superficial (propriedades
abióticas, variação da concentração de clorofila-a e índices fenológicos do fitoplâncton) e
diferentes abordagens metodológicas (métodos de partição e resolução temporal). As
diferentes partições do SWIP foram utilizadas para avaliar os padrões de variabilidade da
biomassa e fenologia do fitoplâncton e suas relações com diferentes forçantes ambientais. No
contexto deste estudo, as variáveis ambientais avaliadas incluíram variáveis locais indicadoras
do ambiente físico, químico e ótico, variáveis hidrológicas indicadoras de processos costeiros
(descarga dos rios e intensidade do afloramento costeiro) e indicadores climáticos de larga
escala.This thesis was supported by Science without Borders Programme from the Brazilian National Council for Scientific and Technological Development (237998/2012‐2