Local‐ and Large‐Scale Drivers of Variability in the Coastal Freshwater Budget of the Western Antarctic Peninsula

Meredith, Michael P.; Stammerjohn, Sharon; Ducklow, Hugh W.; Leng, Melanie J.; Arrowsmith, Carol; Brearley, J. Alexander; Venables, Hugh J.; Barham, Mark; Wessem, Jan Melchior van; Schofield, Oscar; Waite, Nicole

doi:10.1029/2021jc017172

Cited by 14 publications

(16 citation statements)

References 76 publications

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“…An analytical reproducibility of ± 0.02‰ was obtained with duplicate analysis. Using δ 18 O and surface salinity data, we quantitatively separated sea ice melt from meteoric water (glacial melt, precipitation, and runoff from snow melt) by solving a three‐endmember mass balance equation ( see methods and endmember values in Meredith et al 2021). Using this mass balance equation, negative values for sea ice melt are possible and are indicative of net sea ice formation (i.e., more sea ice grew in situ than melted in situ due to lateral advection).…”

Section: Methodsmentioning

confidence: 99%

“…Using this mass balance equation, negative values for sea ice melt are possible and are indicative of net sea ice formation (i.e., more sea ice grew in situ than melted in situ due to lateral advection). Glacial meltwater discharge is a dominant meteoric source in the coastal and nearshore regions of the WAP (Meredith et al 2013(Meredith et al , 2017(Meredith et al , 2021, but here we will continue to refer to this derived metric as "meteoric water" to explicitly reflect the fact that it comprises both precipitation and glacial meltwater inputs.…”

Section: Ancillary Datamentioning

confidence: 99%

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Characterizing coastal phytoplankton seasonal succession patterns on the West Antarctic Peninsula

Nardelli

Gray

Stammerjohn

et al. 2023

Limnology & Oceanography

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In coastal West Antarctic Peninsula (WAP) waters, large phytoplankton blooms in late austral spring fuel a highly productive marine ecosystem. However, WAP atmospheric and oceanic temperatures are rising, winter sea ice extent and duration are decreasing, and summer phytoplankton biomass in the northern WAP has decreased and shifted toward smaller cells. To better understand these relationships, an Imaging FlowCytobot was used to characterize seasonal (spring to autumn) phytoplankton community composition and cell size during a low (2017–2018) and high (2018–2019) chlorophyll a year in relation to physical drivers (e.g., sea ice and meteoric water) at Palmer Station, Antarctica. A shorter sea ice season with early rapid retreat resulted in low phytoplankton biomass with a low proportion of diatoms (2017–2018), while a longer sea ice season with late protracted retreat resulted in the opposite (2018–2019). Despite these differences, phytoplankton seasonal succession was similar in both years: (1) a large‐celled centric diatom bloom during spring sea ice retreat; (2) a peak summer phase comprised of mixotrophic cryptophytes with increases in light and postbloom organic matter; and (3) a late summer phase comprised of small (< 20 μm) diatoms and mixed flagellates with increases in wind‐driven nutrient resuspension. In addition, cell diameter decreased from November to April with increases in meteoric water in both years. The tight coupling between sea ice, meltwater, and phytoplankton species composition suggests that continued warming in the WAP will affect phytoplankton seasonal dynamics, and subsequently seasonal food web dynamics.

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Section: Methodsmentioning

confidence: 99%

Section: Ancillary Datamentioning

confidence: 99%

Characterizing coastal phytoplankton seasonal succession patterns on the West Antarctic Peninsula

Nardelli

Gray

Stammerjohn

et al. 2023

Limnology & Oceanography

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“…In the NAP region, specifically, several studies have reported an increasing contribution of small cryptophytes to the phytoplankton community composition (e.g., Mendes et al, 2013; Mendes, Tavano, Dotto, et al, 2018; Mendes, Tavano, Kerr, et al, 2018), with our decadal in situ dataset suggesting a niche segregation between cryptophytes and diatoms based on physical and chemical properties of the water‐column (Figure S2). The variation in upper ocean physical structures caused by the influence of glacial meltwater input (lower‐salinity waters), which leads to shallower‐stabilized upper layers (Meredith et al, 2021), apparently does not favor the development of diatom bloom (Costa et al, 2021), leaving the well‐lit surface waters free for cryptophytes to grow (Figure S2).…”

Section: Resultsmentioning

confidence: 99%

Cryptophytes: An emerging algal group in the rapidly changing Antarctic Peninsula marine environments

Mendes

Costa

Ferreira

et al. 2023

Global Change Biology

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The western Antarctic Peninsula (WAP) is a climatically sensitive region where foundational changes at the basis of the food web have been recorded; cryptophytes are gradually outgrowing diatoms together with a decreased size spectrum of the phytoplankton community. Based on a 11‐year (2008–2018) in‐situ dataset, we demonstrate a strong coupling between biomass accumulation of cryptophytes, summer upper ocean stability, and the mixed layer depth. Our results shed light on the environmental conditions favoring the cryptophyte success in coastal regions of the WAP, especially during situations of shallower mixed layers associated with lower diatom biomass, which evidences a clear competition or niche segregation between diatoms and cryptophytes. We also unravel the cryptophyte photo‐physiological niche by exploring its capacity to thrive under high light stress normally found in confined stratified upper layers. Such conditions are becoming more frequent in the Antarctic coastal waters and will likely have significant future implications at various levels of the marine food web. The competitive advantage of cryptophytes in environments with significant light level fluctuations was supported by laboratory experiments that revealed a high flexibility of cryptophytes to grow in different light conditions driven by a fast photo‐regulating response. All tested physiological parameters support the hypothesis that cryptophytes are highly flexible regarding their growing light conditions and extremely efficient in rapidly photo‐regulating changes to environmental light levels. This plasticity would give them a competitive advantage in exploiting an ecological niche where light levels fluctuate quickly. These findings provide new insights on niche separation between diatoms and cryptophytes, which is vital for a thorough understanding of the WAP marine ecosystem.

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“…Using this approach, Meredith et al [67] produced new insight into the relative importance of different freshwater inputs to the West Antarctic Peninsula region, an area of very strong climatic sensitivity, and how this importance varies across a range of spatial and temporal scales. Collaborating with the French WAPITI team, Akhoudas et al [68] used δ 18 O to reconcile different quantifications of AABW production and export produced previously using contrasting techniques.…”

Section: (Ii) Tracing Freshwater Inputs With Oxygen Isotopesmentioning

confidence: 99%

Finale: impact of the ORCHESTRA/ENCORE programmes on Southern Ocean heat and carbon understanding

Meijers

Meredith

Shuckburgh

et al. 2023

Phil. Trans. R. Soc. A.

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The 5-year Ocean Regulation of Climate by Heat and Carbon Sequestration and Transports (ORCHESTRA) programme and its 1-year extension ENCORE (ENCORE is the National Capability ORCHESTRA Extension) was an approximately 11-million-pound programme involving seven UK research centres that finished in March 2022. The project sought to radically improve our ability to measure, understand and predict the exchange, storage and export of heat and carbon by the Southern Ocean. It achieved this through a series of milestone observational campaigns in combination with model development and analysis. Twelve cruises in the Weddell Sea and South Atlantic were undertaken, along with mooring, glider and profiler deployments and aircraft missions, all contributing to measurements of internal ocean and air–sea heat and carbon fluxes. Numerous forward and adjoint numerical experiments were developed and supported by the analysis of coupled climate models. The programme has resulted in over 100 peer-reviewed publications to date as well as significant impacts on climate assessments and policy and science coordination groups. Here, we summarize the research highlights of the programme and assess the progress achieved by ORCHESTRA/ENCORE and the questions it raises for the future. This article is part of a discussion meeting issue ‘Heat and carbon uptake in the Southern Ocean: the state of the art and future priorities’.

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Local‐ and Large‐Scale Drivers of Variability in the Coastal Freshwater Budget of the Western Antarctic Peninsula

Cited by 14 publications

References 76 publications

Characterizing coastal phytoplankton seasonal succession patterns on the West Antarctic Peninsula

Characterizing coastal phytoplankton seasonal succession patterns on the West Antarctic Peninsula

Cryptophytes: An emerging algal group in the rapidly changing Antarctic Peninsula marine environments

Finale: impact of the ORCHESTRA/ENCORE programmes on Southern Ocean heat and carbon understanding

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