Elizabeth H. Shadwick

Commonwealth Scientific and Industrial Research Organisation

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Helmuth Thomas

Helmholtz-Zentrum Hereon

Raymond G. Najjar

Pennsylvania State University

Marjorie A. M. Friedrichs

William & Mary

Susanne E. Craig

Goddard Space Flight Center

Bronte Tilbrook

Commonwealth Scientific and Industrial Research Organisation

B. J. W. Greenan

Bedford Institute of Oceanography

Tim Papakyriakou

University of Manitoba

Thomas W. Trull

University of Tasmania

Andrew Lenton

CSIRO Oceans and Atmosphere

Adrienne J. Sutton

NOAA Pacific Marine Environmental Laboratory

Cooperative Institutions

University of Tasmania

Antarctic Climate and Ecosystems Cooperative Research Centre

Australian Antarctic Division

CSIRO Oceans and Atmosphere

Commonwealth Scientific and Industrial Research Organisation

National Oceanic and Atmospheric Administration

Fisheries and Oceans Canada

Centre National de la Recherche Scientifique

Oceanography Society

Dalhousie University

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Mechanistic Constraints on the Drivers of Southern Ocean Meridional Iron Distributions Between Tasmania and Antarctica

Global Biogeochemical Cycles (2024)

Christopher D. Traill Paula C. Pardo Tyler Rohr Pier van der Merwe Ashley T. Townsend

Abstract While modeling efforts have furthered our understanding of marine iron biogeochemistry and its influence on carbon sequestration, observations of dissolved iron (dFe) and its relationship to physical, chemical and biological processes in the ocean are needed to both validate and inform model parameterization. Where iron comes from, how it is transported and recycled, and where iron removal takes place are critical mechanisms that need to be understood to assess the relationship between iron availability and primary production. To this end, hydrographic and trace metal observations across the GO‐SHIP section SR3, south of Tasmania, Australia, have been analyzed in tandem with the novel application of an optimum multiparameter analysis. From the trace‐metal distribution south of Australia, key differences in the drivers of dFe between oceanographic zones of the Southern Ocean were identified. In the subtropical zone, sources of dFe were attributed to waters advected off the continental shelf, and to recirculated modified mode and intermediate water‐masses of the Tasman Outflow. In the subantarctic zone, the seasonal replenishment of dFe in Antarctic surface and mode waters appears to be sustained by iron recycling in the underlying mode and intermediate waters. In the southern zone, the dFe distribution is likely driven by dissolution and scavenging by high concentrations of particles along the Antarctic continental shelf and slope entrained in high salinity shelf water. This approach to trace metal analysis may prove useful in future transects for identifying key mechanisms driving marine dissolved trace metal distributions.

10.1029/2023gb007856

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Annual cycles of pCO_2sw in the southeastern Beaufort Sea: New understandings of air‐sea CO₂ exchange in arctic polynya regions

Journal of Geophysical Research Atmospheres (2012)

Brent Else Tim Papakyriakou R. J. Galley Alfonso Mucci Michel Gosselin

From 23 October 2007 to 1 August 2008, we made continuous measurements of sea surface partial pressure of CO 2 ( p CO 2 sw ) in three regions of the southeastern Beaufort Sea (Canada): the Amundsen Gulf, the Banks Island Shelf, and the Mackenzie Shelf. All three regions are seasonally ice covered, with mobile winter ice and an early spring opening that defines them as polynya regions. Amundsen Gulf was characterized by undersaturated p CO 2 sw (with respect to the atmosphere) in the late fall, followed by an under‐ice increase to near saturation in winter, a return to undersaturation during the spring, and an increase to near saturation in summer. The Banks Island Shelf acted similarly, while the Mackenzie Shelf experienced high supersaturation in the fall, followed by a spring undersaturation and a complex, spatially heterogeneous summer season. None of these patterns are similar to the annual cycle described or proposed for other Arctic polynya regions. We hypothesize that the discrepancy reflects the influence of several previously unconsidered processes including fall phytoplankton blooms, upwelling, winter air‐sea gas exchange, the continental shelf pump, spring nutrient limitation, summer surface warming, horizontal advection, and riverine input. In order to properly predict current and future rates of air‐sea CO 2 exchange in such regions, these processes must be considered on a location‐by‐location basis.

Beaufort sea

Beaufort scale

10.1029/2011jc007346

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Citations (70)

Changes in Southern Ocean Biogeochemistry and the Potential Impact on pH-Sensitive Planktonic Organisms

Oceanography (2021)

Elizabeth H. Shadwick Andrés S. Rigual‐Hernández Ruth Eriksen Peter Jansen Diana M. Davies

The goal of SOTS is to assess air-sea exchange, biological production, and carbon uptake and export in the Subantarctic Zone.Because these exchanges occur over many spatial and temporal scales, for example, from daily insolation cycles to seasonal cycles in biological production and decadal oscillations over whole ocean basins, high-frequency observations collected over many years are required.The current context of relentless anthropogenic forcing of rapid climate change increases the urgency of this work.

Biogeochemistry

Forcing (mathematics)

10.5670/oceanog.2021.supplement.02-06

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Southern Ocean Time Series (SOTS) Quality Assessment and Control Report. Version 1.0. Temperature Records 2006-2019.

Peter Jansen Ben Weeding Elizabeth H. Shadwick Thomas W. Trull

10.26198/gfgr-fq47

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Sea Ice Suppression of CO ₂ Outgassing in the West Antarctic Peninsula: Implications For The Evolving Southern Ocean Carbon Sink

Geophysical Research Letters (2021)

Elizabeth H. Shadwick Olivia A. De Meo Serena Schroeter Mar C. Arroyo Douglas G. Martinson

Abstract The Southern Ocean plays an important role in the uptake of atmospheric CO 2 . In seasonally ice‐covered regions, estimates of air‐sea exchange remain uncertain in part because of a lack of observations outside the summer season. Here we present new estimates of air‐sea CO 2 flux in the West Antarctic Peninsula (WAP) from an autonomous mooring on the continental shelf. In summer, the WAP is a sink for atmospheric CO 2 followed by a slow return to atmospheric equilibrium in autumn and winter. Outgassing is almost entirely suppressed by ice cover from June through October, resulting in a modest net annual CO 2 sink. Model projections indicate sea ice formation will occur later in the season in the coming decades potentially weakening the net oceanic CO 2 sink. Interannual variability in the WAP is significant, highlighting the importance of sustained observations of air‐sea exchange in this rapidly changing region of the Southern Ocean.

Sink (geography)

Outgassing

Peninsula

Carbon sink

10.1029/2020gl091835

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Citations (17)

Biogenic carbon flows through the planktonic food web of the Amundsen Gulf (Arctic Ocean): A synthesis of field measurements and inverse modeling analyses

Progress In Oceanography (2011)

Alexandre Forest Jean‐Éric Tremblay Yves Gratton Johannie Martin Jonathan Gagnon

Microbial food web

Calanus

10.1016/j.pocean.2011.05.002

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Citations (142)

Enhanced ocean carbon storage from anaerobic alkalinity generation in coastal sediments

Biogeosciences (2009)

H. Thomas Laure‐Sophie Schiettecatte K. Suykens Y. J. M. Koné Elizabeth H. Shadwick

Abstract. The coastal ocean is a crucial link between land, the open ocean and the atmosphere. The shallowness of the water column permits close interactions between the sedimentary, aquatic and atmospheric compartments, which otherwise are decoupled at long time scales (≅ 1000 yr) in the open oceans. Despite the prominent role of the coastal oceans in absorbing atmospheric CO2 and transferring it into the deep oceans via the continental shelf pump, the underlying mechanisms remain only partly understood. Evaluating observations from the North Sea, a NW European shelf sea, we provide evidence that anaerobic degradation of organic matter, fuelled from land and ocean, generates total alkalinity (AT) and increases the CO2 buffer capacity of seawater. At both the basin wide and annual scales anaerobic AT generation in the North Sea's tidal mud flat area irreversibly facilitates 7–10%, or taking into consideration benthic denitrification in the North Sea, 20–25% of the North Sea's overall CO2 uptake. At the global scale, anaerobic AT generation could be accountable for as much as 60% of the uptake of CO2 in shelf and marginal seas, making this process, the anaerobic pump, a key player in the biological carbon pump. Under future high CO2 conditions oceanic CO2 storage via the anaerobic pump may even gain further relevance because of stimulated ocean productivity.

Alkalinity

10.5194/bg-6-267-2009

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Citations (194)

A Continental Shelf Pump for CO₂ on the Adélie Land Coast, East Antarctica

Journal of Geophysical Research Oceans (2020)

Mar C. Arroyo Elizabeth H. Shadwick Bronte Tilbrook Stephen R. Rintoul Kazuya Kusahara

Abstract We quantify the transport of inorganic carbon from the continental shelf to the deep ocean in Dense Shelf Water (DSW) from the Mertz and Ninnis Polynyas along the Adélie Land coast in East Antarctica. For this purpose, observations of total dissolved inorganic carbon (TCO 2 ) from two summer hydrographic surveys in 2015 and 2017 were paired with DSW volume transport estimates derived from a coupled ocean‐sea ice‐ice shelf model to examine the fate of inorganic carbon in DSW from Adélie Land. Transports indicate a net outflow of 227 ± 115 Tg C yr −1 with DSW in the postglacial calving configuration of the Mertz Polynya. The greatest outflow of inorganic carbon from the shelf region was delivered through the northern boundary across the Adélie and Mertz Sills, with an additional transport westward from the Mertz Polynya. Inorganic carbon in DSW is derived primarily from inflowing TCO 2 ‐rich modified Circumpolar Deep Water; local processes (biological productivity, air‐sea exchange of CO 2 , and the addition of brine during sea ice formation) make much smaller contributions. This study proposes that DSW export serves as a continental shelf pump for CO 2 and is a pathway to sequester inorganic carbon from the shallow Antarctic continental shelf to the abyssal ocean, removing CO 2 from atmospheric exchange on the time scale of centuries.

Outflow

Circumpolar deep water

10.1029/2020jc016302

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Direct observations of diel biological CO2 fixation on the Scotian Shelf, northwestern Atlantic Ocean

Helmuth Thomas Susanne E. Craig B. J. W. Greenan Wayne V. Burt Gerhard J. Herndl

Diel vertical migration

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Southern Ocean [in “State of the Climate in 2020”]

Bulletin of the American Meteorological Society (2021)

Tamsitt Seth M. Bushinsky Z Li Marcel du Plessis Annie Foppert

The Southern Ocean (SO) plays a unique role in the climate system and is responsible for 40% of oceanic anthropogenic carbon dioxide (CO2) uptake and 75% of the ocean's uptake of heat from the atmosphere (Frolicher et al. 2015). The relatively recent increases in deployments of biogeochemical floats (Claustre et al. 2020), Saildrone Uncrewed Surface Vehicles (USVs; Sutton et al. 2021), and Deep Argo (Roemmich et al. 2019) have provided novel insights into seasonal and interannual variability in SO properties and fluxes. Here, we present 2020 anomalies of SO air–sea heat and CO2 fluxes and show recent changes in mixed layer (ML) and Antarctic Bottom Water (AABW) properties.

Argo

Biogeochemical Cycle

Mixed layer

Antarctic Bottom Water

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