mmaheigan :: Ocean Carbon & Biogeochemistry

Studying marine ecosystems and biogeochemical cycles in the face of environmental change

Author Archive for mmaheigan

OCB workshop report: Towards a better understanding of fish contribution to carbon flux

Posted by mmaheigan

· Friday, April 19th, 2019

This workshop, held March 4-5, 2019 at Rutgers University, was attended by 14 researchers from 11 different institutions. The workshop focused on synthesizing the existing research on fish carbon flux, discussing challenges in measuring fish carbon flux, and determining approaches for estimating fish contribution to carbon flux on variable scales. Presentations and discussions were specifically targeted toward best approaches for determining: fish biomass on regional and global scales, relative amounts of carbon forms produced from fish (i.e., release of sinking fecal pellets, excretion of particulate inorganic carbon and dissolved organic carbon, respiration of carbon dioxide), and carbon flux estimates from fish biomass (i.e., bioenergetics, size-based allometric relationships, stable isotopes). Planned products resulting from this workshop and ongoing working group efforts include two peer-reviewed manuscripts focused on the synthesis of fish carbon flux research and a quantitative analysis of fish carbon flux. Learn more about the working group and view presentations from this workshop on the project’s web page. A full workshop report will be available in the next few months.

Northeast Pacific time-series reveals episodic events as major player in carbon export

Posted by mmaheigan

· Tuesday, April 16th, 2019

Temporal fluctuations in the oceanic carbon budget play an important role in the cycling of organic matter from production in surface waters to consumption and sequestration in the deep ocean. A 29-year time-series (1989-2017) of particulate organic carbon (POC) fluxes and seafloor measurements of oxygen consumption in the abyssal northeast Pacific (Sta. M, 4,000 m depth) recently revealed an increasing proportional contribution from episodic events over the past seven years. From 2011 to 2017, 43% of POC flux arrived during high-magnitude (≥ mean + 2 σ) episodic events. Time lags between changes in satellite-estimated export flux (EF), POC flux to the seafloor, and seafloor oxygen consumption varied from 0 to 70 days among six flux events, which could be attributed to variable remineralization rates and/or particle sinking speeds. The Martin equation, a commonly used model to estimate carbon flux, predicted background fluxes well but missed episodic fluxes, subsequently underestimating the measured fluxes by almost 50% (Figure 1). This study reveals the potential importance of episodic POC pulses into the deep sea in the oceanic carbon budget, which has implications for observing infrastructure, model development, and field campaigns focused on quantifying carbon export.

Figure Caption: (A) Station M POC flux measured from sediment traps compared to Martin model estimates, from 1989 to 2017. (B) Model performance for years with >50% sampling coverage: (POC flux_Martin − POC flux_trap)/POC flux_trap 100.

Authors:
Kenneth Smith (MBARI)
Henry Ruhl (MBARI, NOC)
Christine Huffard (MBARI)
Monique Messié (MBARI, Aix Marseille Université)
Mati Kahru (Scripps)

Ocean color offers early warning signal of climate change’s impact on marine phytoplankton

Posted by mmaheigan

· Monday, April 15th, 2019

Marine phytoplankton form the foundation of the marine food web and play a crucial role in the earth’s carbon cycle. Typically, satellite-derived Chlorophyll a (Chl a) is used to evaluate trends in phytoplankton. However, it may be many decades (or longer) before we see a statistically significant signature of climate change in Chl a due to its inherently large natural variability. In a recent study in Nature Communications, authors explored how other metrics, in particular the color of the ocean, may show earlier and stronger signals of climate change at the base of the marine food web.

Figure 1. Computer model results indicating the year in which the signature of climate change impact is larger than the natural variability for (a) Chl a, and (b) remotely sensed reflectance in the blue-green waveband. White areas indicate where there is not a statistically significant change by 2100, or for regions that are currently ice-covered.

In this study, the authors use a unique marine physical-biogeochemical and ecosystem model that also captures how light penetrates the ocean and is reflected upward. The model shows that over the course of the 21^st century, remote sensing reflectance (R_RS, the ratio of upwelling radiance to the downwelling irradiance at the ocean’s surface) in the blue-green portions of the light spectrum is likely to have an earlier, more spatially extensive climate change-driven signal than Chl a (Figure 1). This is because R_RS integrates not only changes to Chl a, but also alterations in other optically important water constituents. In particular, R_RS also captures changes in phytoplankton community structure, which strongly affects ocean optics and is likely to be altered over the 21^st century. Monitoring the response of marine phytoplankton to climate change is important for predicting changes at higher trophic levels, including commercial fisheries. Our study emphasizes the importance of 1) maintaining ocean color sensor compatibility and long-term stability, particularly in the blue-green wavebands; 2) maintaining long-term in situ time-series of plankton communities – e.g., the Continuous Plankton Recorder survey and repeat stations (e.g., HOT, BATS); and 3) reducing uncertainties in satellite-derived phytoplankton community structure estimates.

Authors:
Stephanie Dutkiewicz, Oliver Jahn (Massachusetts Institute of Technology)
Anna E. Hickman (University of Southampton)
Stephanie Henson (National Oceanography Centre Southampton)
Claudie Beaulieu (University of California, Santa Cruz)
Erwan Monier (University of California, Davis)

Antarctic Ocean CO2 helped end the ice age

Posted by mmaheigan

· Tuesday, April 2nd, 2019

Many scientists have long hypothesized that the ocean around Antarctica was responsible for changing CO₂ levels during ice ages, but lacked definitive evidence. A new study in Nature provides the most direct evidence of this process to date and provides crucial evidence of the mechanisms—including changing sea ice cover and bipolar seesaw (warming in the Southern Hemisphere during cooling in the Northern Hemisphere) events—that controlled CO₂ and climate during the ice ages.

Using samples of fossil deep-sea corals collected from 1000 m in the Drake Passage (Figure 1a), the authors were able to reconstruct the CO₂ content of the deep ocean. They found that the deep ocean CO₂ record was the “mirror image” of CO₂ in the atmosphere (Figure 1b), with the ocean storing CO₂ during an ice age and releasing it back to the atmosphere during deglaciation. CO₂ rise during the last ice age occurred in a series of steps and jumps associated with intervals of rapid climate change.

As well as helping scientists better understand the ice ages, the new findings also provide context to current CO₂ rise and climate change. Although the CO₂ rise that helped end the last ice age was dramatic in geological terms, CO₂ rise due to human activity over the last 100 years is even larger and about 100 times faster. CO₂ rise at the end of the ice age helped drive major melting of ice sheets resulting in sea level rise of >100 meters. These results bolster the idea that if we want to prevent dangerous levels of global warming and sea level rise in the future, we need to reduce CO₂ emissions as quickly as possible

Authors:
J. W. B. Rae (University of St Andrews, UK)
A. Burke (University of St Andrews, UK)
L. F. Robinson (University of Bristol, UK)
J. F. Adkins (California Institute of Technology)
T. Chen (University of Bristol, UK, Nanjing University, China)
C. Cole (University of St Andrews, UK)
R. Greenop (University of St Andrews, UK)
T. Li (University of Bristol, UK, Nanjing University, China)
E. F. M. Littley (University of St Andrews, UK)
D. C. Nita (University of St Andrews, UK, Babes-Bolyai University, Romania)
J. A. Stewart (University of St Andrews, UK, University of Bristol, UK)
B. J. Taylor (University of St Andrews, UK)

A half century perspective: Seasonal productivity and particulates in the Ross Sea

Posted by mmaheigan

· Tuesday, April 2nd, 2019

Studies of cruise observations in the Ross Sea are typically biased to a single or a few year(s), and long-term trends have predominantly come from satellites. Consequently, the in situ climatological patterns of nutrients and particulate matter have remained vague and unclear. What are the typical patterns of nutrients and particulate matter concentrations in the Ross Sea in spring and summer? How do these concentrations affect annual productivity estimates?

Patterns of nutrient and particulate matter in the Ross Sea can play a wide-ranging role in a productive region like the Ross Sea. Smith and Kaufman (2018) recently synthesized austral spring and summer (November to February) observations from 42 Ross Sea research cruises (1967-2016) to analyze broad biogeochemical patterns. The resulting climatologies revealed interesting seasonal patterns of nutrient uptake and particulate organic carbon (POC) to chlorophyll (chl) ratios (POC:chl). Temporal patterns in the nitrate and phosphate climatologies confirm the role of early spring haptophyte (Phaeocystis antarctica) growth, followed by limited nitrogen and phosphorus removal in summer. However, a notable increase in POC occurred later in summer that was largely independent of chlorophyll changes, resulting in a dramatic increase in POC:chl. A gradual decline in silicic acid concentrations throughout the summer, along with an increased occurrence of biogenic silica during this time suggest that diatoms may be responsible for this later POC spike. Revised estimates of primary productivity based on these observed climatological POC:chl ratios suggests that summer blooms may be a significant contributor to seasonal productivity, and that estimates of productivity based on satellite pigments underestimate annual production by at least 70% (Figure 1).

Figure 1. Bio-optical estimates of mean productivity using a constant POC:chl ratio (black dots and lines) and modified estimates of productivity using the monthly climatological POC:chl ratios (red dots and lines), in a) the Ross Sea polynya region and b) the western Ross Sea region.

By clarifying typical seasonal patterns of nutrient uptake and POC:chl, these climatologies underscore the biogeochemical importance of both spring haptophyte growth and previously underestimated summer diatom growth in the Ross Sea. Further investigation of the causes and consequences of elevated summer ratios is needed, as assessments of regional food webs and biogeochemical cycles depend on more accurate understanding of primary productivity patterns. Likewise, these results highlight the need for continued efforts to constrain satellite productivity estimates in the Ross Sea using in situ constituent ratios.

For other relevant work on seasonal biogeochemical patterns in the Ross Sea, please see https://doi.org/10.1016/j.dsr2.2003.07.010. And for intra-seasonal estimates of particulate organic carbon to chlorophyll using gliders, please see: https://doi.org/10.1016/j.dsr.2014.06.011.

Authors:
Walker O. Smith Jr. (VIMS, College of William and Mary)
Daniel E. Kaufman (VIMS, College of William and Mary; now at Chesapeake Research Consortium)

OCB2019 Registration is OPEN!

Posted by mmaheigan

· Monday, April 1st, 2019

Register here

Please register early, as space is limited and registration will close when we reach 180 participants.

Registration fees are used to cover your lodging, meals and other on site workshop costs. Please see the workshop Logistics page for more details on costs and travel.

The 2019 OCB Summer Workshop will be held June 24-27, 2019 in Woods Hole, MA.

2019 OCB Workshop Plenary Sessions

Anthropogenic changes in ocean oxygen: Coastal and open ocean perspectives (Monday)
Chairs: Julie Granger, Adam Martiny, Alyson Santoro, and Ben Twining
Session Description: Warming waters, shifting circulation and ventilation, and coastal eutrophication are driving changes in dissolved oxygen levels in the coastal and open oceans. These changes have impacts on carbon and nutrient biogeochemistry, as well as the health of pelagic and benthic communities. At the same time, naturally occurring seasonal and interannual variability in dissolved oxygen complicates discerning the magnitude and even the sign of long term trends. This session will explore changes in oxygen concentrations observed across a range of environments (coastal to open ocean), while considering a range of physical, biological, and anthropogenic drivers of these changes, as well as their impacts.
Speakers: Andreas Oschlies (GEOMAR), Matthew Long (NCAR), Samantha Siedlecki (Univ. Conn), Malcolm Scully (WHOI), Jerry Tjiputra (UniResearch, Norway) and Mariona Claret (U. Washington), Jeremy Testa (UMCES), Denise Breitburg (Smithsonian Institute)

Approaches and challenges to understanding biogeochemical cycling across the land-ocean aquatic continuum (Tuesday)
Chairs: Marjy Friedrichs, Eileen Hofmann, Raleigh Hood, and Maria Tzortziou
Session Description: Despite their small area, the network of rivers, estuaries, and continental shelf waters that comprise the land-ocean continuum are central to global biogeochemical cycling, which has significant implications for ecosystem services such as carbon sequestration. Changes in land use and the effects of climate change are altering biogeochemical cycling across this interlinked continuum, often with detrimental effects, manifested as hypoxia and coastal acidification, for example. The ability to predict outcomes resulting from these changes and to develop scenarios for projections of possible future states is limited by understanding of linkages across this continuum. This session is intended to provide assessments of the current state of understanding of biogeochemical cycling across the land-ocean continuum, evaluations of current and needed approaches for observing and modeling system components, assessment of fluxes to the coastal ocean, and discussions of the challenges of development of future state scenarios.
Speakers: Xiao Liu (Princeton University and NOAA GFDL), Tom Bianchi (Univ. Florida), Iris Anderson (VIMS), and more speakers to be announced soon!

Calcification and the carbon cycle (Wednesday)
Chairs: Andrea Fassbender and Jessica Cross
Session Description: 2018 was a year of notable discovery regarding ocean carbonate chemistry, prompting community reflection on important aspects of the marine carbon cycle that are not yet fully understood. One of the major findings relates to changing seasonal cycle amplitudes for carbonate system parameters (e.g., pCO₂, [H⁺], and saturation state) caused by rising ocean temperatures and anthropogenic carbon concentrations. This phenomenon has been anticipated and hypothesized in the literature for over a decade; however, observational evidence at a global scale was just documented for pCO₂ in 2018. Complementary modeling work in the last year has also highlighted some of the implications for marine organisms that may be sensitive to pH and calcium carbonate saturation states in both coastal and open ocean regions. In recognition of these findings, this session will consider linkages between ocean chemistry and marine calcification from observational and modeling perspectives. This topic is particularly relevant due to an ongoing discussions in the community regarding which component of the carbonate chemistry (e.g., dissolved inorganic carbon and [H⁺] vs. saturation state) drives calcification.
Speakers: Andrea Fassbender (MBARI), Lennart Bach (GEOMAR/IMAS Hobart), Bernard Boudreau (Dalhousie), Weifu Guo (WHOI), Kristen Krumhardt (NCAR), George Waldbusser (OSU)

Carbon cycle feedbacks from the seafloor (Wednesday)
Chair: Clare Reimers
Session Description: The seafloor from shallow coastal regimes to the hadal ocean is an interface where carbon is cycled between dissolved and particulate forms, and organic and inorganic pools. This cycling can be the basis of major ecosystems and critical to the biogeochemical cycling of other elements. This session will focus on recent advances in approaches for characterizing the dynamics of benthic carbon cycling and fluxes and on the consequences of these processes. Topics will include seasonal assessments of benthic carbon metabolism within nearshore and shelf regions, the effects of anthropogenic CO₂ invasion into the ocean on calcification and carbonate dissolution in sediments, the effects of warming on gas hydrate destabilization, and carbon mineralization in ocean trenches.
Speakers: Clare Reimers (OSU), Kristen Fogaren (Oregon State Univ.), Amelie Berger (Univ. Virginia), Ronnie Glud (Univ. Southern Denmark), Kathryn Sparrow (FSU), Olivier Sulpis (McGill Univ.)

The effect of size on ocean processes (allometry) and implications for export (Thursday)
Chair: Amy Maas
Session Description: Currently many major models use a suite of allometric relationships to describe and simplify complex interactions in natural systems and predict biogeochemical cycling. This session will describe current effective marine applications of allometry at a range of scales (organismal to ecosystem), but will also present research on the physiology and ecology of oceanic groups that highlight when allometry fails to constrain important variation. We will discuss a suite of alternative/supplementary “master traits” that appear to be informative, as well as the feasibility of including these in modeling efforts.
Speakers: Amy Mass (BIOS), Nick Nidzieko (UCSB), Anand Gnanadesikan (The Johns Hopkins Univ.), Karen Stamieszkin (VIMS), Ken Andersen (Technical University of Denmark)

Moore Foundation – Symbiosis in Aquatic Systems Initiative

Posted by mmaheigan

· Monday, April 1st, 2019

The Symbiosis in Aquatic Systems Initiative of the Gordon and Betty Moore Foundation is soliciting pre-applications for investigator awards. Investigators will be selected based on their potential to conduct research that illuminates how aquatic symbioses involving microbes function, and how these interactions shape ecology and evolution in marine and freshwater habitats. The deadline for submitting a pre-application is June 3, 2019 at 23:59 PDT. To learn more about this funding opportunity, including FAQs and eligibility information and to apply, please follow this link: https://symbiosis.smapply.io.

Nitrous Oxide and Methane in the Ocean – new workshop video!

Posted by mmaheigan

· Thursday, March 28th, 2019

New short video about trace gases and the 2018 Methane & Nitrous Oxide workshop!

In October 2018, an Ocean Carbon & Biogeochemistry (OCB)-sponsored workshop addressed questions to help determine the future directions of methane and nitrous oxide measurements in the global oceans. The workshop was designed to sit at the interface between laboratory analysis of trace gases, our comprehension of the relevant microbial processes, and our observational and predictive capacity to resolve spatial-temporal variability associated with methane and nitrous oxide in the oceans. The objective was to define the key questions that need to be addressed in the near future and provide practical guidance about how they can be addressed.

Please visit the website at https://web.whoi.edu/methane-workshop/ for more about oceanic methane and nitrous oxide, and about the 2018 workshop.

GLODAP2_2019 Release

Posted by mmaheigan

· Wednesday, March 27th, 2019

Global Ocean Data Analysis Project (GLODAP) version 2 includes data from approximately one million individual seawater samples collected from almost 800 cruises carried during the years 1972-2013. Extensive quality control and subsequent calibration were carried out for salinity, oxygen, nutrient, carbon dioxide, total alkalinity, pH and chlorofluorocarbon data. Following calibration, the data were used to produce global climatology maps for many of the parameters. In addition to the data products and the mapped distributions, all of the original data files without alteration other than formatting and unification of units are made freely available along with whatever metadata was collected. An on-line cruise summary table provides data access and additional information including references to publications that have used data from specific cruises.

Learn more at https://www.glodap.info/ and http://www.ioccp.org/index.php/more/506-global-ocean-data-analysis-project-glodapv2-2019-released
Data are available at NCEI; https://www.nodc.noaa.gov/ocads/oceans/GLODAPv2_2019/

LDEO (Takahashi) Database Version 2018

Posted by mmaheigan

· Wednesday, March 27th, 2019

The LDEO (Takahashi) Database Version 2018 (LDEO_Database_V2018) was published at OCADS/NCEI/NOAA: https://www.nodc.noaa.gov/ocads/oceans/LDEO_Underway_Database/

Approximately 13.5 million measurements of surface water pCO₂ made over the global oceans during 1957-2018 have been processed to make a uniform data file in this Version 2018. Measurements made in open oceans as well as in coastal waters are included. The data assembled include only those measured using equilibrator-CO₂ analyzer systems, and have been quality-controlled based upon the stability of the system performance, the reliability of calibrations for CO₂ analysis and the internal consistency of data.

Thank you,
Alex Kozyr – NOAA Affiliate
NOAA National Centers for Environmental Information
Phone:+1-865-216-4499
Email: alex.kozyr@noaa.gov
NOAA Ocean Carbon Data System (OCADS) Project

Funding for the Ocean Carbon & Biogeochemistry Project Office is provided by the National Science Foundation (NSF) and the National Aeronautics and Space Administration (NASA). The OCB Project Office is housed at the Woods Hole Oceanographic Institution.

Author Archive for mmaheigan

2019 OCB Workshop Plenary Sessions

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