Variability and change in the west Antarctic Peninsula marine system: Research priorities and opportunities

Abstract

The west Antarctic Peninsula (WAP) region has undergone significant changes in temperature and seasonal ice dynamics since the mid-twentieth century, with strong impacts on the regional ecosystem, ocean chemistry and hydrographic properties. Changes to these long-term trends of warming and sea ice decline have been observed in the 21 st century, but their consequences for ocean physics, chemistry and the ecology of the high-productivity shelf ecosystem are yet to be fully established. The WAP shelf is important for regional krill stocks and higher trophic levels, whilst the degree of variability and change in the physical environment and documented biological and biogeochemical responses make this a model system for how climate and sea ice changes might restructure high-latitude ecosystems. Although this region is arguably the best-measured and bestunderstood shelf region around Antarctica, significant gaps remain in spatial and temporal data capable of resolving the atmosphere-ice-ocean-ecosystem feedbacks that control the dynamics and evolution of this complex polar system. Here we summarise the current state of knowledge regarding the key mechanisms and interactions regulating the physical, biogeochemical and biological processes at work, the ways in which the shelf environment is changing, and the ecosystem response to the changes underway. We outline the overarching cross-disciplinary priorities for future research, as well as the most important discipline-specific objectives. Underpinning these priorities and objectives is the need to better-define the causes, magnitude and timescales of variability and change at all levels of the system. A combination of traditional and innovative approaches will be critical to addressing these priorities and developing a coordinated observing system for the WAP shelf, which is required to detect and elucidate change into the future.

Antarctic phytoplankton community composition and size structure: importance of ice type and temperature as regulatory factors

“…It may be that previous associations of cryptophytes with salinity were largely driven by collinearity between salinity and temperature. Alternatively, differences in species-specific responses to environmental variables could also be responsible for the variances observed (Henley et al 2019).…”

“…However, the physicochemical drivers behind community shifts towards flagellated phytoplankton remain unclear, likely due to the diversity among flagellated phytoplankton spanning different taxonomic groups and cell sizes, and each may interact differently with the physicochemical environment. Our current understanding of the drivers associated with the seasonal progression within the phytoplankton community (Henley et al 2019), particularly the pico-(≤ 3 µm) and nano-sized (> 3-20 µm) phytoplankton, limits our ability to accurately predict how polar marine systems will respond to future climate change with implications for food-web dynamics and the marine carbon cycle (e.g. Pinhassi et al 2004;Conan et al 2007;Christaki et al 2008;Obernosterer et al 2008;Agustí and Duarte 2013;Evans et al 2017).…”

Abiotic Changes Driving Microphytoplankton Functional Diversity in Admiralty Bay, King George Island (Antarctica)

“…It should be noted that although the phytoplankton community and events of Antarctic blooms are commonly dominated by diatoms, other taxa are also important components of the trophic web (Henley et al, 2019). Increases in cryptophytes and other flagellates have previously been reported (e.g., Phaeocystis antarctica and Gymnodiniales), as well as the substitution of diatoms for these flagellates in WAP, due to the influence of sea ice melt (Moline et al, 2004;Mendes et al, 2013;Lange et al, 2014;Mendes et al, 2017), as observed in the WAP sectors of the present study (Figure 3): sector 1 (Wasiłowska et al, 2015), sector 4 (Mendes et al, 2012(Mendes et al, , 2013, oceanic regions of sectors 5 (Mar de Weddell) and 6 (Passagem de Drake) (Mendes et al, 2012), as well as sectors 7 (Mendes et al, 2018), 9 (Gerlache Strait) (Mendes et al, 2017;Russo et al, 2018) and 11 (Arrigo et al, 2017).…”

The interaction between island geomorphology and environmental parameters drives Adélie penguin breeding phenology on neighboring islands near Palmer Station, Antarctica

“…The WAP has been warming since at least the 1950s with increasing winter air temperature and precipitation (Kirchgäßner, ). During our study period, there was no trend in precipitation, and after decades of sea ice decline from 1970 to 2009 (most notably the ice season became shorter), sea ice began to rebuild along the WAP after reaching a local minimum in 2008–2009 (i.e., the annual ice season became longer post‐2008–2009) (Henley et al, ; Schofield et al, ). In general, to detect an ecologically relevant trend in phenological datasets it may be necessary to consider and evaluate environmental conditions over the same temporal scales.…”

“…We tested for a trend in the estimated Adélie penguin mean CID over time. It has been recently recognized that sea ice trends began leveling off or reversing along the WAP since about 2008–2009 when a local minimum in annual ice season duration was observed, after which there was an increase in the length of the annual ice season (Henley et al, ; Schofield et al, ), at least until ~2016. Therefore, using linear regression, we tested for trends in observed CIDs and predicted CIDs over time by assessing the time series before and after this local minimum.…”