The waters along the West Antarctic Peninsula (WAP) have experienced warming and increased freshwater inputs from melting sea ice and glaciers in recent decades. Challenges exist in understanding the consequences of these changes on the inorganic carbon system in this ecologically important and highly productive ecosystem. Distributions of dissolved inorganic carbon (CT), total alkalinity (AT) and nutrients revealed key physical, biological and biogeochemical controls of the calcium carbonate saturation state (Ωaragonite) in different water masses across the WAP shelf during the summer. Biological production in spring and summer dominated changes in surface water Ωaragonite (ΔΩaragonite up to +1.39; ~90%) relative to underlying Winter Water. Sea-ice and glacial meltwater constituted a minor source of AT that increased surface water Ωaragonite (ΔΩaragonite up to +0.07; ~13%). Remineralization of organic matter and an influx of carbon-rich brines led to cross-shelf decreases in Ωaragonite in Winter Water and Circumpolar Deep Water. A strong biological carbon pump over the shelf created Ωaragonite oversaturation in surface waters and suppression of Ωaragonite in subsurface waters. Undersaturation of aragonite occurred at < ~1000 m. Ongoing changes along the WAP will impact the biologically driven and meltwater-driven processes that influence the vulnerability of shelf waters to calcium carbonate undersaturation in the future.

The temporal and spatial variability of oceanographic properties in Potter Cove was analysed for the 2010–17 summer periods. This was linked with meteorological parameters and sea ice. The water column structure presented significant differences in turbidity between two areas (away from and closer to the Fourcade Glacier). The recent retreat has been transforming it into a land terminating glacier. Therefore, correlations obtained between oceanographic properties near the glacier and meteorological parameters reveal that atmospheric conditions are the main forcing of the Potter system, in agreement with previous studies. Also, high turbidity values within deeper waters in 2013 and 2014 were probably related to resuspended glacial sediment input into the cove. Interannual variability observed in the local parameters was connected to ENSO and SAM, reflecting a larger connection with ENSO, mainly in longer timescales. Colder waters during the 2010 and 2016 El Niño phases could be related to lower air temperature. In summer 2010 during a negative SAM phase, colder, more saline and low turbid waters were observed. Alternatively, in 2012 during La Niña and positive SAM, warmer, fresher and more turbid conditions were found with high vertical stratification. Finally, during 2015 (positive SAM), warmer and low salinity waters were observed.

Using the positive degree days approach and ERA-Interim reanalysis downscaled data, the researchers ran a melt model spatially gridded at 200 m with annual temporal resolution over 32 years and estimated surface melt (SM) and surface runoff (SR) on the Antarctic Peninsula. The model was calibrated and validated independently by field measurements. The maximum surface melt values occurred in 1985 (129 Gt), and the maximum runoff (40 Gt) occurred in 1993; both parameters showed minimum values in 2014 (26 Gt and 0.37 Gt, respectively). No significant trends are present. Two widespread positive anomalies occurred in 1993 and 2006. The results reveal that the floating ice areas produce an average of 68% of runoff and 61% of surface melt, emphasizing their importance to coastal hydrography. During the seven years preceding the Larsen B collapse, surface melt retention was higher than 95% on floating ice areas, and negative runoff anomalies persisted. Excluding the islands, the vicinity of this former ice shelf exhibits the highest specific surface melt and runoff across the studied area.

The surface waters of the Southern Ocean play a key role in the global climate and carbon cycles by promoting growth of some of the world’s largest phytoplankton blooms. Several studies have emphasized the importance of glacial and sediment inputs of Fe that fuel the primary production of the Fe-limited Southern Ocean. Although the fertile surface waters along the shelf of the western Antarctic Peninsula (WAP) are influenced by large inputs of freshwater, this freshwater may take multiple pathways (e.g. calving, streams, groundwater discharge) with different degrees of water-rock interactions leading to variable Fe flux to coastal waters. During the summers of 2012–13 and 2013–14, seawater samples were collected along the WAP, near Anvers Island, to observe water column dynamics in nearshore and offshore waters. Tracers (223,224Ra, 222Rn, 18O, 2H) were used to evaluate the source and transport of water and nutrients in coastal fjords and across the shelf. Coastal waters are compared across two field seasons, with increased freshwater observed during 2014. Horizontal mixing rates of water masses along the WAP ranged from 110–3600 m2 s-1. These mixing rates suggest a rapid transport mechanism for moving meltwater offshore.

Icebergs calved from tidewater glaciers represent about one third to one half of the freshwater flux from the Greenland ice sheet to the surrounding ocean. Using multiple satellite datasets, we quantify the first fjord-wide distributions of iceberg sizes and characteristics for three fjords with distinct hydrography and geometry: Sermilik Fjord, Rink Isbræ Fjord and Kangerlussuup Sermia Fjord. We estimate average total iceberg volumes in summer in the three fjords to be 6.4 ± 1.5, 1.7 ± 0.40 and 0.16 ± 0.09 km3, respectively. Iceberg properties are influenced by glacier calving style and grounding line depth, with variations in size distribution represented by exponents of power law distributions that are −1.95 ± 0.06, −1.87 ± 0.05 and −1.62 ± 0.04, respectively. The underwater surface area of icebergs exceeds the subsurface area of glacial termini by at least one order of magnitude in all three fjords, underscoring the need to include iceberg melt in fjord freshwater budgets. Indeed, in Sermilik Fjord, we calculate summertime freshwater flux from iceberg melt of 620 m3 s−1 (±140 m3 s−1), similar in magnitude to subglacial discharge. The method developed here can be extended across Greenland to assess relationships between glacier calving, iceberg discharge and freshwater production.

The McMurdo Dry Valleys of Antarctica are the largest ice-free region on the continent. These valleys contain numerous water bodies that receive seasonal melt from glaciers. For forty years, research emphasis has been placed on the larger water bodies, the permanent ice-covered lakes. We present results from the first study describing the geochemistry of ponds in the higher elevations of Taylor Valley. Unlike the lakes at lower elevations, the landscape on which these ponds lie is among the oldest in Taylor Valley. These upland ponds wax and wane in size depending on the local climatic conditions, and their ionic concentrations and isotopic composition vary annually depending on the amount of meltwater generated and their hydrologic connectivity. This study evaluates the impact of changes in summer climate on the chemistry of these ponds. Although pond chemistry reflects the initial meltwater chemistry, dissolution and chemical weathering within the stream channels, and possibly permafrost fluid input, the primary control is the dilution effect of glacier melt during warmer summers. These processes lead to differences in solute concentrations and ionic ratios between ponds, despite their nearby proximity. The change in size of these ponds over time has important consequences on their geochemical behaviour and potential to provide water and solutes to the subsurface.

Glacial and post-glacial shelf sedimentation near the Larsen C and former Larsen B ice shelves is compared to records from ice shelves farther north, which underwent mid-Holocene retreat. A core from Larsen C comprises a lower unit of deformation till, overlain by thick mud interpreted as water lain from suspension under the ice shelf. Iceberg-rafted debris occurs only in the top 50 cm, suggesting that prior to that layer's deposition, the ice shelf had not receded past the site since the last deglaciation. Subsequently the site appears to have been seasonally ice free, and the ice shelf has retreated further and is now 15 km landward of the site. A core from Larsen B also consists of a lower unit, interpreted as sub-glacial lodgement till. The overlying mud is thinner, more poorly sorted, with evidence of powerful winnowing of sediments suggesting strong currents. The absence of iceberg-rafted debris implies that this site was covered by an ice shelf continuously from the last deglaciation until its collapse in 2002. Strong currents could have facilitated basal erosion, contributing to its collapse. The Larsen C shelf is also thinning and historical records show retreat in the last hundred years. With continued rising temperatures, Larsen C may eventually retreat to a point at which it collapses.

Oxygen isotope ratios in the shell of a Recent Antarctic marine bivalve Laternula elliptica are shown and their potential for environmental reconstruction is discussed. The shell δ18O profiles of this species represent the seasonal change in melted ice water inflow. Oscillations in the shell δ18O values reflect seasonal change in seawater δ18O values, caused by an addition of meltwater in summer. Since annual temperature variation is minimal and the inflow of the regional ice-melt is the dominant control on the shell δ18O values, the oxygen isotope record of L. elliptica is a quantitative indicator of the palaeo-ice-melting events in the Antarctic continental margin.

Two geochemical surveys of the major constituents of the Alph River, situated in Walcott Bay, Victoria Land, were undertaken in the austral summer of 1987–88. At the same time, tributaries and the runoff from various glaciers were investigated. The Alph River has an average total dissolved solids (TDS) concentration of 63.5 mgl−1, approximately half that of average world river water. The chemical composition is dominated by Na+ and HCO−3. Glacial melt waters have very low TDS but chemical weathering over the course of a few kilometres causes solute concentrations in the tributaries to exceed those of the Alph River. The composition of the streams is variable, but often Ca2+ is the principal cation. Enrichment factor and mass balance calculations indicate that the salts in the Alph River and its tributaries have a substantial non-marine component. Chemical weathering of calcite, mirabilite, gypsum and halite contribute solutes to the aquatic system. A “Gibbs Plot” [TDS versus Na:(Na+Ca) weight ratio] indicates that water samples from direct glacial runoff fall outside the world water envelope. They have low solute levels but enhanced Ca2+ concentrations, resulting from the aeolian deposition and subsequent dissolution of calcitic material.

Melt waters cover c. 20% of the McMurdo Ice Shelf during the austral summer. The streams, ponds, and lakes up to 104 m2 in area occur in two types of terrain systems with differing morphological, chemical, and biological characteristics: pinnacled ice (PI) areas with sparse sediment cover, low relief, and little biomass; and ice-cored moraine (ICM) areas with 10–20 cm sediment cover, hummocky topography with up to 20 m relief, occasional mirabilite deposits, and dense benthic cyanobacterial mats. Pond water composition in the two areas is markedly different. PI area melt waters have low salinities, <2270 mg 1−1 total dissolved salts (TDS), and near neutral pH, mean = 7.8. The chemical composition of PI waters closely follows that of diluted sea water, suggesting that the release of ions from the sea ice matrix of the ice shelf is the major solute source. In contrast, ICM area melt waters have a wide range of salinities, up to 60 400 mg 1−1 TDS and alkaline pH, mean = 9.3. The chemical composition in c. 40% of the ICM ponds investigated did not resemble that of sea water, but had higher relative abundances of SO2−4, Na+, K+ and Ca2+. Leaching of local salt deposits, particularly mirabilite, weathering of surficial sediments, and morphological features promoting closed-basin brine evolution are possible contributing factors to the enrichments.

The distribution of dimethylsulphide (DMS), together with the precursor dimethylsulphonio-propionate (DMSP) and the oxidation product dimethylsulphoxide (DMSO), was measured in melt waters on the McMurdo Ice Shelf in the immediate vicinity of Bratina Island. Conductivity in these sulphate dominated ponds was extremely variable, ranging from 0.106–52.3 mS cm−1. Similarly, chlorophyll a concentrations in the pond waters (1–150 μg 1−1) and mats (1.4–33 μg cm−2) differed considerably. The biomass was dominated by benthic felts of phototrophic cyanobacteria, which might act as a source of biogenic sulphur compounds in the ponds. The mean (and ranges) of concentrations of dissolved sulphur compounds (nmol 1−1) were: CS2 0.16 (<0.04–1.29); DMSPd 0.6 (<0.07–8.4); DMS 3.5 (<0.07–183); DMSO 27.9 (15.5–184.5). Very high concentrations of DMSO were ubiquitous in the ponds in the ice-cored moraine region of the ice shelf, with dissolved concentrations having been 1–2 orders of magnitude greater than those of DMS or DMSPd. It is difficult to ascribe the formation of DMSO solely to the conventionally accepted pathways of DMS oxidation by either bacterial activity or photochemical reactions. A direct biosynthetic production from phytoplankton or bacteria might be involved which means that DMSO in aquatic environments could act as a significant source of DMS rather than as a sink as generally supposed.

Two short gravity cores were retrieved to obtain palaeoclimatic information from Maxwell and Admiralty bays, King George Island, South Shetland Islands. AMS 14C age dates, sediment properties (grain size, TOC and CaCO3) and stable oxygen and carbon isotope compositions of benthiδ foraminifera (Globocassidulina biora) show downcore variations that characterize depositional conditions during the late Holocene. In particular, δ18O values of benthic foraminifera are lowest at approximately 2500 yr bp in both cores. Allowδ18O time-equivalent excursion in both cores is interpreted to reflect a distinct subglacial meltwater discharge intensified by warm climatic conditions. An increased proportion of fine-grained detritus and higher TOC in the cores at this level suggests that enhanced meltwater supply may have resulted in increased primary productivity. This meltwater discharge event provides evidence of climatic instability during the late Holocene at King George Island.