Supplementary material to "Utilizing the Drake Passage Time-series to understand variability and change in subpolar Southern Ocean pCO2"

Abstract. The Southern Ocean is highly under-sampled for the purpose of assessing total carbon uptake and its variability. Since this region dominates the mean global ocean sink for anthropogenic carbon, understanding temporal change is critical. Underway measurements of pCO2 collected as part of the Drake Passage Time-series (DPT) program that began in 2002 inform our understanding of seasonally changing air-sea gradients in pCO2, and by inference the carbon flux in this region. Here, we utilize all available pCO2 observations collected in the subpolar Southern Ocean to evaluate how the seasonal cycle, interannual variability, and long-term trends in surface ocean pCO2 in the Drake Passage region compare to that of the broader subpolar Southern Ocean. Our results indicate that the Drake Passage is representative of the broader region in both seasonality and long term pCO2 trends shown through the agreement of timing and amplitude of seasonal cycles as well as trend magnitudes. The high temporal density of sampling by the DPT is critical to constraining estimates of the seasonal cycle of surface pCO2 in this region, as winter data remain sparse in areas outside of the Drake Passage. From 2002–2015, data show that carbon uptake has strengthened with surface ocean pCO2 trends less than the global atmospheric trend in the Drake Passage and the broader subpolar Southern Ocean. Analysis of spatial correlation shows Drake Passage pCO2 to be representative of pCO2 and its variability up to several hundred kilometers upstream of the region. We also compare DPT data from 2016 and early 2017 to contemporaneous pCO2 estimates from autonomous biogeochemical floats deployed as part of the Southern Ocean Carbon and Climate Observations and Modeling project (SOCCOM) so as to highlight the opportunity for evaluating data collected on autonomous observational platforms. Though SOCCOM floats sparsely sample the Drake Passage region for 2016–2017, their pCO2 estimates typically fall within the range of underway observations. Going forward, continuation of the Drake Passage Time-series will reduce uncertainties in Southern Ocean carbon uptake seasonality, variability, and trends, and provide an invaluable independent dataset for post-deployment quality control of sensors on autonomous floats. Together, these datasets will vastly increase our ability to monitor change in the ocean carbon sink.

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Utilizing the Drake Passage Time-series to understand variability and change in subpolar Southern Ocean pCO2

Biogeosciences ◽

10.5194/bg-15-3841-2018 ◽

2018 ◽

Vol 15 (12) ◽

pp. 3841-3855 ◽

Cited By ~ 12

Author(s):

Amanda R. Fay ◽

Nicole S. Lovenduski ◽

Galen A. McKinley ◽

David R. Munro ◽

Colm Sweeney ◽

...

Keyword(s):

Time Series ◽

Southern Ocean ◽

Seasonal Cycle ◽

Drake Passage ◽

Passage Time ◽

Global Ocean ◽

Carbon Uptake ◽

Surface Ocean ◽

Ocean Carbon

Abstract. The Southern Ocean is highly under-sampled for the purpose of assessing total carbon uptake and its variability. Since this region dominates the mean global ocean sink for anthropogenic carbon, understanding temporal change is critical. Underway measurements of pCO2 collected as part of the Drake Passage Time-series (DPT) program that began in 2002 inform our understanding of seasonally changing air–sea gradients in pCO2, and by inference the carbon flux in this region. Here, we utilize available pCO2 observations to evaluate how the seasonal cycle, interannual variability, and long-term trends in surface ocean pCO2 in the Drake Passage region compare to that of the broader subpolar Southern Ocean. Our results indicate that the Drake Passage is representative of the broader region in both seasonality and long-term pCO2 trends, as evident through the agreement of timing and amplitude of seasonal cycles as well as trend magnitudes both seasonally and annually. The high temporal density of sampling by the DPT is critical to constraining estimates of the seasonal cycle of surface pCO2 in this region, as winter data remain sparse in areas outside of the Drake Passage. An increase in winter data would aid in reduction of uncertainty levels. On average over the period 2002–2016, data show that carbon uptake has strengthened with annual surface ocean pCO2 trends in the Drake Passage and the broader subpolar Southern Ocean less than the global atmospheric trend. Analysis of spatial correlation shows Drake Passage pCO2 to be representative of pCO2 and its variability up to several hundred kilometers away from the region. We also compare DPT data from 2016 and 2017 to contemporaneous pCO2 estimates from autonomous biogeochemical floats deployed as part of the Southern Ocean Carbon and Climate Observations and Modeling project (SOCCOM) so as to highlight the opportunity for evaluating data collected on autonomous observational platforms. Though SOCCOM floats sparsely sample the Drake Passage region for 2016–2017 compared to the Drake Passage Time-series, their pCO2 estimates fall within the range of underway observations given the uncertainty on the estimates. Going forward, continuation of the Drake Passage Time-series will reduce uncertainties in Southern Ocean carbon uptake seasonality, variability, and trends, and provide an invaluable independent dataset for post-deployment assessment of sensors on autonomous floats. Together, these datasets will vastly increase our ability to monitor change in the ocean carbon sink.

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Constructing a Time Series for Southern Ocean Currents Using GRACE

10.5194/gstm2020-67 ◽

2020 ◽

Author(s):

Jordan Meyer ◽

Don Chambers

Keyword(s):

Time Series ◽

Southern Ocean ◽

Real Life ◽

Drake Passage ◽

Life Time ◽

Ocean Basin ◽

Pressure Gradients ◽

Bottom Pressure ◽

University Of Texas ◽

The Antarctic

The currents of the Southern Ocean connect to every ocean basin and distribute water between them, making these currents an important quantity to monitor and understand as they change over time. In situ instrumentation is difficult to deploy within this region, however these currents create bottom pressure signals at major bathymetric obstacles which are observable by the GRACE and GRACE Follow-On satellites.&#160; &#160;&#160;&#160; In this study, we examine the relationships between the Antarctic Circumpolar Current and the Antarctic Bottom Water within the Southern Ocean and the bottom pressure gradients at the Kerguelen Plateau seamount and the Drake Passage sill using the high resolution Southern Ocean State Estimate. Then we use these relationships along with bottom pressure gradients from the RL05 and RL06 mascon solutions from the Center for Space Research at the University of Texas at Austin to develop a real-life time series of the two currents.

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Estimates of net community production in the Southern Ocean determined from time series observations (2002–2011) of nutrients, dissolved inorganic carbon, and surface ocean pCO2 in Drake Passage

Deep Sea Research Part II Topical Studies in Oceanography ◽

10.1016/j.dsr2.2014.12.014 ◽

2015 ◽

Vol 114 ◽

pp. 49-63 ◽

Cited By ~ 27

Author(s):

David R. Munro ◽

Nicole S. Lovenduski ◽

Britton B. Stephens ◽

Timothy Newberger ◽

Kevin R. Arrigo ◽

...

Keyword(s):

Time Series ◽

Southern Ocean ◽

Inorganic Carbon ◽

Dissolved Inorganic Carbon ◽

Drake Passage ◽

Net Community Production ◽

Surface Ocean ◽

Community Production

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Antarctic Peninsula sea levels: a real-time system for monitoring Drake Passage transport

Antarctic Science ◽

10.1017/s0954102006000472 ◽

2006 ◽

Vol 18 (3) ◽

pp. 429-436 ◽

Cited By ~ 10

Author(s):

P.L. Woodworth ◽

C.W. Hughes ◽

D.L. Blackman ◽

V.N. Stepanov ◽

S.J. Holgate ◽

...

Keyword(s):

Southern Ocean ◽

Real Time ◽

Antarctic Peninsula ◽

Tide Gauge ◽

Drake Passage ◽

Southern Annular Mode ◽

Time System ◽

International Polar Year ◽

Real Time System ◽

Sea Levels

Sub-surface pressure (SSP) data from tide gauges at three bases on the Pacific coast of the Antarctic Peninsula, together with SSP information from a bottom pressure recorder deployed on the south side of the Drake Passage, have been used to study the relationships between SSP, Drake Passage transport, and the strength of Southern Ocean zonal winds as represented by the Southern Annular Mode. High correlations were obtained between all parameters, confirming results obtained previously with independent data sets, and demonstrating the value of information from the permanent Rothera base, the southern-most site considered. These are important findings with regard to the design, installation and maintenance of observation networks in Antarctica. In particular, they provide the necessary justification for Antarctic Peninsula tide gauge infrastructure investment in the lead up to International Polar Year. Data delivery from Rothera and Vernadsky is currently being improved and should soon enable the first near real-time system for monitoring Drake Passage transport variability on intraseasonal timescales, an essential component of a Southern Ocean Observing System.

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Manganese co-limitation of phytoplankton growth and major nutrient drawdown in the Southern Ocean

Nature Communications ◽

10.1038/s41467-021-21122-6 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Thomas J. Browning ◽

Eric P. Achterberg ◽

Anja Engel ◽

Edward Mawji

Keyword(s):

Southern Ocean ◽

Drake Passage ◽

Phytoplankton Growth ◽

South American ◽

Cold Temperatures ◽

Continental Shelves ◽

Ocean Productivity ◽

Major Nutrient ◽

Essential Function ◽

Glacial Periods

AbstractResidual macronutrients in the surface Southern Ocean result from restricted biological utilization, caused by low wintertime irradiance, cold temperatures, and insufficient micronutrients. Variability in utilization alters oceanic CO2 sequestration at glacial-interglacial timescales. The role for insufficient iron has been examined in detail, but manganese also has an essential function in photosynthesis and dissolved concentrations in the Southern Ocean can be strongly depleted. However, clear evidence for or against manganese limitation in this system is lacking. Here we present results from ten experiments distributed across Drake Passage. We found manganese (co-)limited phytoplankton growth and macronutrient consumption in central Drake Passage, whilst iron limitation was widespread nearer the South American and Antarctic continental shelves. Spatial patterns were reconciled with the different rates and timescales for removal of each element from seawater. Our results suggest an important role for manganese in modelling Southern Ocean productivity and understanding major nutrient drawdown in glacial periods.

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An Eddy-Permitting Southern Ocean State Estimate

Journal of Physical Oceanography ◽

10.1175/2009jpo4236.1 ◽

2010 ◽

Vol 40 (5) ◽

pp. 880-899 ◽

Cited By ~ 218

Author(s):

Matthew R. Mazloff ◽

Patrick Heimbach ◽

Carl Wunsch

Keyword(s):

Southern Ocean ◽

General Circulation Model ◽

General Circulation ◽

Microwave Radiometer ◽

World Ocean ◽

Circulation Model ◽

Great Majority ◽

Drake Passage ◽

Volume Transport ◽

Intermediate Cell

Abstract An eddy-permitting general circulation model of the Southern Ocean is fit by constrained least squares to a large observational dataset during 2005–06. Data used include Argo float profiles, CTD synoptic sections, Southern Elephant Seals as Oceanographic Samplers (SEaOS) instrument-mounted seal profiles, XBTs, altimetric observations [Envisat, Geosat, Jason-1, and Ocean Topography Experiment (TOPEX)/Poseidon], and infrared and microwave radiometer observed sea surface temperature. An adjoint model is used to determine descent directions in minimizing a misfit function, each of whose elements has been weighted by an estimate of the observational plus model error. The model is brought into near agreement with the data by adjusting its control vector, here consisting of initial and meteorological boundary conditions. Although total consistency has not yet been achieved, the existing solution is in good agreement with the great majority of the 2005 and 2006 Southern Ocean observations and better represents these data than does the World Ocean Atlas 2001 (WOA01) climatological product. The estimate captures the oceanic temporal variability and in this respect represents a major improvement upon earlier static inverse estimates. During the estimation period, the Drake Passage volume transport is 153 ± 5 Sv (1 Sv ≡ 106 m3 s−1). The Ross and Weddell polar gyre transports are 20 ± 5 Sv and 40 ± 8 Sv, respectively. Across 32°S there is a surface meridional overturning cell of 12 ± 12 Sv, an intermediate cell of 17 ± 12 Sv, and an abyssal cell of 13 ± 6 Sv. The northward heat and freshwater anomaly transports across 30°S are −0.3 PW and 0.7 Sv, with estimated uncertainties of 0.5 PW and 0.2 Sv. The net rate of wind work is 2.1 ± 1.1 TW. Southern Ocean theories involving short temporal- and spatial-scale dynamics may now be tested with a dynamically and thermodynamically realistic general circulation model solution that is known to be compatible with the modern observational datasets.

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