Daniela Turk

We present high-resolution autonomous measurements of carbon dioxide partial pressure <i>p</i>(CO<sub>2</sub>) taken in situ at the Porcupine Abyssal Plain sustained Observatory (PAP-SO) in the northeast Atlantic (49° N, 16.5° W; water depth of 4850 m) for the period 2010–2012. Measurements of <i>p</i>(CO<sub>2</sub>) made at 30 m depth on a sensor frame are compared with other autonomous biogeochemical measurements at that depth (including chlorophyll <i>a</i> fluorescence and nitrate concentration data) to analyse weekly to seasonal controls on <i>p</i>(CO<sub>2</sub>) flux in the inter-gyre region of the North Atlantic. Comparisons are also made with in situ regional time series data from a ship of opportunity and mixed layer depth (MLD) measurements from profiling Argo floats. There is a persistent under-saturation of CO<sub>2</sub> in surface waters throughout the year which ...

Recent studies indicate that the western equatorial Pacific Warm Pool may play an important role in interannual and decadal climate variation, global new production, and global atmosphere CO2 concentration. In this study, I compared the rates of new production and air-sea exchange of CO 2 in the western equatorial Pacific Warm Pool during normal conditions (December 1995/January 1996 and January 1997), during a moderate El Niño event (November/December 1994), and during the strongest El Niño event (December 1997/January 1998) in recent history. As an aid for interpreting and understanding of these processes I used both direct measurements and a box model. Direct measurements of the rate of nitrate uptake (new production) along the equator (from 145°E to 165°W) show that interannual variations in new production in the western and central equatorial Pacific correlate well with the change of the nutricline depth during the eastward expansion of the Warm Pool depending strongly upon the severity of the El Niño event. The analysis of nitrate, carbon, and heat balances in the western equatorial Pacific indicates that-in non-El Niño conditions-vertical turbulent diffusion is primarily responsible for both the loss of heat and the supply of nitrate and inorganic carbon to the euphotic zone. Based on this conclusion on the importance of vertical processes, I developed a box model that allows estimation of the rates of new production and air-sea CO2 exchange in the Warm Pool from the net surface heat flux, elemental ratios, and the C:N ratio of the organic matter sinking from the euphotic zone. The model predictions agree qualitatively with the direct measurements. The model may provide a means for estimating the rates of new production and air-sea CO2 exchange over the large areas of equatorial Pacific using the remotely- sensed data. The results of this study may also be useful in further understanding of the role of the western equatorial Pacific in biogeochemical cycles and climate variations, and for assessment of this part of the ocean for future fisheries demands.

Diverse instruments, both custom built and commercially available, have been used to measure the properties of the aqueous CO2 system in seawater at differing levels of autonomy (automated benchtop, continuous underway, autonomous in situ). In this review, we compare the capabilities of commercially available instruments with the needs of oceanographers in order to highlight major shortfalls in the state-of-the art instrumentation broadly available to the ocean acidification (OA) scientific community. In addition, we describe community surveys that identify needs for continued development and refinement of sensor and instrument technologies, expansion of programs that provide Certified Reference Materials, development of best practices documentation for autonomous sensors, and continued and expanded sensor intercomparison experiments.

This poster presents an overview and the first accomplishments of the Canadian SOLAS Network. The scientific focus of the Canadian SOLAS research effort largely reflects its integration with the International SOLAS Project and its stated objective of addressing the key interactions among the marine biogeochemical system, the atmosphere and climate, and how this system affects and is affected by past and future climate and environmental changes. Two major expeditions in the Pacific and Atlantic will provide the data to address C-SOLAS objectives; In July, 2002 a mesoscale Fe-addition experiment was carried out in the subarctic Pacific to determine the influence of this limiting trace nutrient on biological production and resulting dynamic changes in the cycling of climatically relevant gases. In 2003, three cruises in the northwest Atlantic are planned to quantify the impact of the spring bloom on trace gasses production and exchange. The responses in the two ecosystems will be compa...

ABSTRACT The importance of interannual fluctuations of the coupled climate system over the tropical Pacific Ocean have been known for quite some time as a result of the El Nino-~ Southern Oscillation (ENSO) phenomenon. The significance of interannual variability in biological production and ecosystem structure in the tropical Pacific for the global carbon cycle has been suggested, but only recently available satellite and buoy obser- vations may provide means to synoptically monitor the magnitude of this variability over the large area of the tropical Pacific. Here, we use a unique combination of ship observations, TAO buoy array data, TOPEX/Poseidon altimeter, and SeaWiFS ocean color to study the variation in bi- ological production and f-ratio during 1997-1999 El Nino and La Nina events in the equatorial Pacific basin. The results are compared to direct measurements, and the consequences for interannual variability in the planetary carbon cycle and ecosystem structure are discussed.

ABSTRACT A massive bloom of phytoplankton in the normally oligotrophic Western Pacific was the first manifestation of the termination of the 1997-1998 El Nino, by most measures, the strongest on record. This bloom represented a 4-fold increase in the background chlorophyll distribution, as viewed by the Sea-Viewing, Wide Field of View Sensor (SeaWiFS). A combination of physical and bio-optical observations from satellites, moored buoys, and ships lead to the conclusion that this bloom was a direct result of the interaction of surface currents with a series of island atolls (Kiribati) that induced strong vertical mixing and subsequent downstream advection of waters rich in nutrients. The increase in phytoplankton concentration represents a lower limit to a dramatically increased level of exported carbon from the normally biologically poor western Pacific region, and is a novel observation of topographic influences which are not normally resolved by most models of equatorial ocean dynamics.

ABSTRACT The importance of interannual fluctuations of the coupled climate system over the Pacific Ocean have been known for quite some time as a result of El Niño phenomenon. The significance of interannual variability in biological production and ecosystem structure in tropical Pacific for global carbon cycle has been suggested, but only recently available satellite and buoy observations provide means to synoptically monitor the magnitude of the variability over the large area of the Pacific Ocean. Here, we provide independent remotely-sensed measures of total and new production, and examine the f-ratio over large space scales in the equatorial Pacific. The purpose is to examine the coherence between the two independent measures, and to evaluate the nature of the physical and ecological processes and structure that give rise to observed variability over interannual time scales.

Recent studies indicate that the western equatorial Pacific Warm Pool may play an important role in interannual and decadal climate variation, global new production, and global atmosphere CO2 concentration. In this study, I compared the rates of new production and air-sea exchange of CO 2 in the western equatorial Pacific Warm Pool during normal conditions (December 1995/January 1996 and January 1997), during a moderate El Niño event (November/December 1994), and during the strongest El Niño event (December 1997/January 1998) in recent history. As an aid for interpreting and understanding of these processes I used both direct measurements and a box model. Direct measurements of the rate of nitrate uptake (new production) along the equator (from 145°E to 165°W) show that interannual variations in new production in the western and central equatorial Pacific correlate well with the change of the nutricline depth during the eastward expansion of the Warm Pool depending strongly upon the...

ABSTRACT Episodic high wind events have a potential for significantly mixing surface water partial pressure of CO2 (pCO2). Their effect on estimates of air–sea CO2 flux, especially in the coastal ocean, has not been adequately assessed. Here we show the response of surface water pCO2 and CO2 fluxes during high bora wind in the Northern Adriatic for a range of conditions including: stratified and oversaturated with respect to atmospheric CO2, stratified and undersaturated, and non-stratified and undersaturated. Three representative bora cases of 1.5–2 day duration with wind speeds over 10 m s− 1 indicate that in all three studied cases, regardless of pre-bora conditions, pCO2 in the surface water increases by 30–50 μatm and CO2 flux magnitudes peak up to 4 folds (− 22.6 and − 24.1 mmol m− 2 day− 1 day in the winter cases and 29 mmol m− 2 day− 1 in the summer case) over the magnitude of the mean annual value. Oceanic data measured simultaneously to surface pCO2 measurements suggest that the most likely responsible mechanisms for the observed pCO2 increases were oceanic vertical mixing and/or oceanic horizontal advection. Our study contributes to a very limited set of observations currently available on the biogeochemical response to episodic high wind events in coastal areas and their role in CO2 exchange. In such coastal environments the presence of shallow depths and short horizontal spatial scales of variation facilitate the exchange of pCO2 both vertically within ocean layers and horizontally across ocean basins, which can then alter air-sea pCO2 difference across the ocean surface during high wind events and affect gas exchange.

Coastal marine regions such as the Gulf of Trieste GOT in the Northern Adriatic Sea serve as the link between carbon cycling on land and the ocean interior and potentially contribute large uncertainties in the estimate of anthropogenic CO2 uptake. This system may be either a sink or a source for atmospheric CO2. Understanding the sources and sinks as a result of biological and physical controls for air-sea carbon dioxide fluxes in coastal waters may substantially alter the current view of the global carbon budget for unique terrestrial and ocean regions such as the GOT. GOT is a semi-enclosed Mediterranean basin situated in the northern part of Adriatic Sea. It is one of the most productive regions in the Mediterranean and is affected by extreme fresh river input, phytoplankton blooms, and large changes of air-sea exchange during Bora high wind events. The unique combination of these environmental processes and relatively small size of the area makes the region an excellent study site for investigations of air-sea interaction, and changes in biology and carbon chemistry. However, there is a dearth of current data or information from the region. Here we present the first measurements of air and water CO2 flux in the GOT. The aqueous CO2 was measured at the Coastal Oceanographic buoy Piran, Slovenia using the SAMI CO2 sensor during spring and late summer and fall 2007. CO2 measurements were combined with hydrological and biological observations to evaluate the processes that control carbon cycling in the region.

Coastal marine regions such as the Gulf of Trieste (GOT) in the Northern Adriatic Sea serve as the link between carbon cycling on land and the ocean interior and potentially contribute large uncertainties in the estimate of anthropogenic CO2 uptake. This system may be either a sink or a source for atmospheric CO2. Understanding the sources and sinks as a

ABSTRACT There is at present significant discussion on whether coral reefs and seagrass beds would be affected by ocean pH changes in ocean surface water related to the continuing increase of carbon dioxide in the atmosphere. While coral reefs are negatively impacted by OA, seagrass may benefit by increasing levels of CO2 and may even mitigate some OA impacts on coral reefs. Here, we examine net ecosystem productivity (NEP) and net ecosystem calcification (NEC) and indicators of the physiology of coral colonies and seagrasses based on measurements made in October 2012 near Sugarloaf Key, in the lower Florida Keys. The main objectives of the study were to determine the primary environmental factors that control diurnal variations in net community production and calcification, including the timing when NEC=0 for coral reef communities. We compare different approaches to assess these processes including Submersible Habitat for Analyzing Reef Quality (SHARQ), vertical dissolved oxygen gradient measurements using a Coral Reef Oxygen Sensing System (CROSS) and SeaFET pH sensor. The effects of episodic thunderstorms on coral NEP is also explored.