Glacial meltwater dynamics in coastal waters west of the Antarctic peninsula

Abstract

The annual advance and retreat of sea ice has been considered a major physical determinant of spatial and temporal changes in the structure of the Antarctic coastal marine ecosystem. However, the role of glacial meltwater on the hydrography of the Antarctic Peninsula ecosystem has been largely ignored, and the resulting biological effects have only been considered within a few kilometers from shore. Through several lines of evidence collected in conjunction with the Palmer Station Long-Term Ecological Research Project, we show that the freshening and warming of the coastal surface water over the summer months is influenced not solely by sea ice melt, as suggested by the literature, but largely by the influx of glacial meltwater. Moreover, the seasonal variability in the amount and extent of the glacial meltwater plume plays a critical role in the functioning of the biota by influencing the physical dynamics of the water (e.g., water column stratification, nearshore turbidity). From nearly a decade of observations (1991-1999), the presence of surface meltwater is correlated not only to phytoplankton blooms nearshore, but spatially over 100 km offshore. The amount of meltwater will also have important secondary effects on the ecosystem by influencing the timing of sea ice formation. Because air temperatures are statistically increasing along the Antarctic Peninsula region, the presence of glacial meltwater is likely to become more prevalent in these surface waters and continue to play an ever-increasing role in driving this fragile ecosystem.

Differences in heavy metal concentrations and in the response of the antioxidant system to hypoxia and air exposure in the Antarctic limpet Nacella concinna

“…However, other factors such as increased input of lithogenic particles from underneath melting glaciers and from eroding land surfaces during the austral summer (Ahn et al, 1997;Klöser et al, 1994;Yoo et al, 1999) are bound to primarily affect the sub-littoral limpet fauna in the coastal environment of this volcanic archipelago (Ahn et al, 2002). Plumes of volcanic rock sediments carry high concentrations of heavy metals including Fe, Al, Cu and Zn into the nearshore waters of the South Shetland Archipelago Dick et al, 2007), and similar phenomena are described from areas along the maritime AP (Dierssen et al, 2002). Once taken up by sedimentary grazers or benthic filter feeders, these metals can exacerbate oxidative stress in animal tissues.…”

Changing distributions of sea ice melt and meteoric water west of the Antarctic Peninsula

“…One manifestation of this is the role of freshwater in stabilising the water column: a thin layer of ice melt will act to enhance stratification, and thus create an environment more favourable for phytoplankton blooms, whereas processes that reduce stratification (e.g. strong ice production in winter) can have the opposite effect (Dierssen et al, 2002;Mitchell and Holm-Hansen, 1991). In northern Marguerite Bay (adjacent to Adelaide Island; Figure 1a), decreases in sea ice cover since 1998 have resulted 6 in deeper winter mixed layers, and consequently reduced stratification and phytoplankton concentration in spring .…”

“…Scouring of the underlying rock and sediment, in addition to accumulation from atmospheric deposition, can result in glacial ice being significantly enriched in such micronutrients (Boyd and Ellwood, 2010). It has been suggested that an increase in freshwater input to the ocean from glaciers could result in a greater injection of such micronutrients (Hawkings et al, 2014), a shift in phytoplankton assemblage composition, and an increase in biomass in the waters influenced (Dierssen et al, 2002).…”

Is the umbo matrix of bivalve shells (Laternula elliptica) a climate archive?

“…The present study was designed to investigate, whether accelerated glacier melting observed over the past 10 years in Potter cove (see Abele et al, 2007;Schloss et al, 2007;Dierssen et al, 2002) might have caused an increase in Fe and of other elements, contained in ablated sediments and dust minerals, in the ultimate growth bands formed in bivalve umbos from the impacted region. Contrary to our hypothesis, element concentrations were highest in the early growth bands formed in the young bivalves and levelled off during the first 6-8 years of bivalve age.…”

“…Samples were taken in Potter Cove on King George Island, Antarctica, fronting the Collins glacier. High loads of particulate and dissolved iron are transported into Potter Cove during the austral summer season with glacier melt water run-off (Schloss et al, 2007;Abele et al, 2007), creating an interest in the idea that bivalve shells might be useful archives of long-term changes of environmental iron load under conditions of climate-induced glaciers melting in the Antarctic Peninsula region (Dierssen et al, 2002). (Philipp et al, 2005) and is a major circum-Antarctic biomass component, colonizing muddy sediments in coastal environments.…”