Production In Ice Research Articles

O atom production in water ice: Implications for O2 formation on icy satellites

We have found that O atoms are a primary product in the irradiation of water‐ice with 0.8 MeV protons. This observation has implications in understanding the chemical reactions that occur to produce molecular oxygen (O2) in such laboratory ices, as well as ices found on the surfaces of Ganymede and Europa, and the ice particles present in Saturn's rings. We estimate that in irradiated water‐ice, O2 can be formed at a lower limit of 0.07% by number relative to water and is in agreement with observations of the icy Jovian satellites.

Physical structure and vertical distribution of chlorophyll a in winter sea ice from the northwestern Weddell Sea, Antarctica

The investigation on sea-ice biology in combination with physics, chemistry and ecology was carried out in the northwestern Weddell Sea, Antarctica, during the cruise ANT/XX III-7 on board POLARSTERN in the austral winter (August–October) in 2006. The distribution of chlorophyll a was measured and related to sea ice texture. The mean concentrations of chlorophyll a in the sea ice varied considerably with ice texture. The concentration of chlorophyll a per core ranged from 2.10–84.40 µg/dm3 with a mean of 16.56 µg/dm3. And the value of R (chlorophyll a / gross chlorophyll) ranged from 0.79–0.83. These high winter chlorophyll values indicate that primary production is considerable and confirms that there is significant primary production in Antarctic sea ice during winter. Thus this constitutes a major proportion of southern ocean primary production and carbon flux before the sea ice retreats.

Spatial and temporal variability of ice algal production in a 3D ice–ocean model of the Hudson Bay, Hudson Strait and Foxe Basin system

Primary production, the basic component of the food web and a sink for dissolved inorganic carbon, is a major unknown in Arctic seas, particularly ice algal production, for which detailed and comprehensive studies are often limited in space and time. We present here a simple ice alga model and its coupling with a regional 3D ice–ocean model of the Hudson Bay system (HBS), including Hudson Strait and Foxe Basin, as a first attempt to estimate ice algal production and its potential contribution to the pelagic ecosystem on a regional scale. The ice algal growth rate is forced by sub-ice light and nutrient availability, whereas grazing and ice melt control biomass loss from the underside of the ice. The simulation shows the primary role of sea-ice dynamics on the distribution and production of ice algae with a high spatio-temporal variability in response to the great variability of ice conditions in different parts of the HBS. In addition to favourable light and nutrient conditions, there must be a sufficient time lag between the onset of sufficient light and ice melt to ensure significant ice algal production. This suggests that, in the context of enhanced warming in Arctic and sub-Arctic regions, earlier melt could be more damaging for ice algal production than later freezing. The model also includes a particulate organic matter (POM) variable, fed by ice melting losses to the water column, and shows a large redistribution of the POM produced by the ice ecosystem on a regional scale.

Microalgal composition and primary production in Arctic sea ice: a seasonal study from Kobbefjord (Kangerluarsunnguaq), West Greenland

We investigated the microalgal community in sea ice and in the water column of Kobbe- fjord, West Greenland, through an entire sea ice season. Temporal variation in physical (photosynthet- ically active radiation (PAR), temperature, brine volume) and chemical (salinity, nutrient concentra- tion) properties confirmed that sea ice is a very dynamic habitat. Nevertheless, a viable sea ice algal community was present throughout the year, with a species succession from flagellate dominance (di- noflagellates and cryptophytes) in December to February, followed by Chaetoceros simplex (a centric diatom) in March and pennate diatoms in May. Sea ice algal composition, biomass and productivity were influenced by PAR and brine volume, with colonization (enhanced by large brine volume) appar- ent during sea ice melt. Sea ice chlorophyll levels were generally low (<0.5 µg chl l -1 ), with 2 distinct blooms (maxima of 1.8 and 2.6 µg chl l -1 in March and May, respectively). Primary production mirrored biomass dynamic, which had 2 seasonal peaks of ca. 21 and 15 mg C m -2 d -1 . Integrated primary pro- duction over 7 mo was 0.8 g C m -2 in sea ice and 94.4 g C m -2 in the water column, with the vast major- ity of the pelagic production occurring just after sea ice melt (when primary production peaked at 4.2 g C m -2 d -1 ). There was no conclusive evidence of algal seeding. Sea ice algae contributed 30% of total (sympagic plus pelagic) primary production during the sea ice season, but less than 1% annually.

Estimation of hooded seal (Cystophora cristata) pup production in the Greenland Sea pack ice during the 2005 whelping season

In March 2005 aerial surveys were carried out to estimate pup production of Greenland Sea hooded seals, Cystophora cristata in three whelping patches using photographic strip transects. The majority of whelping occurred 17–23 March and surveys were carried out on 24 March. The temporal distribution of births and estimated proportion of solitary bluebacks present within the survey area were used to correct the abundance estimates. The total estimated pup production (15,250 pups, s.e. = 3,470; CV = 22.8%) was lower than an estimate from a comparable study in 1997. The current estimate is considered to be negatively biased, as it is uncorrected for pups born outside the whelping concentrations. Population modeling suggests a substantial decline with subsequent stabilization at a lower level for Greenland Sea hooded seals in recent decades. It is suggested that future research on the population explore possible factors (e.g. reduced fertility, predation, food shortage, disease, reductions in ice cover) that may have contributed to the apparent prevailing low abundance.

A novel method for obtaining very large ancient air samples from ablating glacial ice for analyses of methane radiocarbon

AbstractWe present techniques for obtaining large (∼100 L STP) samples of ancient air for analysis of 14C of methane (14CH4)and other trace constituents. Paleoatmospheric 14CH4 measurements should constrain the fossil fraction of past methane budgets, as well as provide a definitive test of methane clathrate involvement in large and rapid methane concentration ([CH4]) increases that accompanied rapid warming events during the last deglaciation. Air dating to the Younger Dryas–Preboreal and Oldest Dryas–Bølling abrupt climatic transitions was obtained by melt extraction from old glacial ice outcropping at an ablation margin in West Greenland. The outcropping ice and occluded air were dated using a combination of δ15N of N2, δ18O of O2, δ18Oice and [CH4] measurements. The [CH4] blank of the melt extractions was &lt;4 ppb. Measurements of δ18O and δ15N indicated no significant gas isotopic fractionation from handling. Measured Ar/N2, CFC-11 and CFC-12 in the samples indicated no significant contamination from ambient air. Ar/N2, Kr/Ar and Xe/Ar ratios in the samples were used to quantify effects of gas dissolution during the melt extractions and correct the sample [CH4]. Corrected [CH4] is elevated over expected values by up to 132 ppb for most samples, suggesting some in situ CH4 production in ice at this site.

Carbon cycling in a high-arctic marine ecosystem – Young Sound, NE Greenland

Young Sound is a deep-sill fjord in NE Greenland (74°N). Sea ice usually begins to form in late September and gains a thickness of ∼1.5 m topped with 0–40 cm of snow before breaking up in mid-July the following year. Primary production starts in spring when sea ice algae begin to flourish at the ice–water interface. Most biomass accumulation occurs in the lower parts of the sea ice, but sea ice algae are observed throughout the sea ice matrix. However, sea ice algal primary production in the fjord is low and often contributes only a few percent of the annual phytoplankton production. Following the break-up of ice, the immediate increase in light penetration to the water column causes a steep increase in pelagic primary production. Usually, the bloom lasts until August–September when nutrients begin to limit production in surface waters and sea ice starts to form. The grazer community, dominated by copepods, soon takes advantage of the increased phytoplankton production, and on an annual basis their carbon demand (7–11 g C m −2) is similar to phytoplankton production (6–10 g C m −2). Furthermore, the carbon demand of pelagic bacteria amounts to 7–12 g C m −2 yr −1. Thus, the carbon demand of the heterotrophic plankton is approximately twice the estimated pelagic primary production, illustrating the importance of advected carbon from the Greenland Sea and from land in fuelling the ecosystem. In the shallow parts of the fjord (<40 m) benthic primary producers dominate primary production. As a minimum estimate, a total of 41 g C m −2 yr −1 is fixed by primary production, of which phytoplankton contributes 15%, sea ice algae <1%, benthic macrophytes 62% and benthic microphytes 22%. A high and diverse benthic infauna dominated by polychaetes and bivalves exists in these shallow-water sediments (<40 m), which are colonized by benthic primary producers and in direct contact with the pelagic phytoplankton bloom. The annual benthic mineralization is 32 g C m −2 yr −1 of which megafauna accounts for 17%. In deeper waters benthic mineralization is 40% lower than in shallow waters and megafauna, primarily brittle stars, accounts for 27% of the benthic mineralization. The carbon that escapes degradation is permanently accumulated in the sediment, and for the locality investigated a rate of 7 g C m −2 yr −1 was determined. A group of walruses (up to 50 adult males) feed in the area in shallow waters (<40 m) during the short, productive, ice-free period, and they have been shown to be able to consume <3% of the standing stock of bivalves ( Hiatella arctica, Mya truncata and Serripes Groenlandicus), or half of the annual bivalve somatic production. Feeding at greater depths is negligible in comparison with their feeding in the bivalve-rich shallow waters.

Profiles of dimethylsulphoniopropionate (DMSP), algal pigments, nutrients, and salinity in the fast ice of Prydz Bay, Antarctica

Total dimethylsulphoniopropionate (DMSPt), chlorophylla(Chla), and algal marker pigments were measured in 12 fast ice cores collected from Prydz Bay, eastern Antarctica (68°–69°S, 77°–79°E) in October 1997 and November 1998. Patterns of DMSPt distribution through the ice were similar on spatial scales of meters to tens of kilometers within ice sheets grouped according to growth history. This reflects the association of DMSP in fast ice with autotrophic biomass distribution, which is intrinsically linked with ice growth and differed between the ice sheets. The 12 fast ice cores were divided into three groups on the basis of ice thickness and year. Concentrations of DMSPt ranged widely from 9 to 1478 nM with marked peaks occurring within each core. Mean DMSPt concentrations were higher (200 nM) in the medium first‐year ice (0.7–1.2 m) than in the thick (&gt;1.2 m) first‐year ice (90 nM), mainly because of a local surface algal assemblage that may be atypical. The fast ice algal assemblages in surface, interior, and bottom ice were dominated by diatoms (Fucoxanthin:Chlaconcentrations &gt;80%). Dinoflagellates and haptophytes were generally small and variable components of the assemblages (Peridinin:Chla2–11% and 19′‐hexanoyloxyfucoxanthin:Chla2–4%, respectively). Our data support the important contribution of diatoms to DMSP production in sea ice. Nutrient (nitrate, silicate, phosphate) concentrations were measured for one group of cores. Silicate and Chlaconcentrations were significantly correlated (r = 0.30, P &lt; 0.02, Pearson), implying that silicate availability may have regulated algal growth. The Si:P:N ratio in interior ice (27:1:10) was different to that in surface and bottom ice (46:1:23). We have summarized DMSP data reported from six Antarctic sea ice studies to investigate whether comparisons within the growing database need to consider differences in sea ice type, thickness, location, or season. Although concentrations from individual samples ranged over 4 orders of magnitude (&lt;1 to &gt;1000 nM,n= 410), the mean DMSP concentrations during spring/summer were within the range of 107–322 nM, with an overall mean of 178 nM. Mean DMSP concentrations in Antarctic sea ice appear to be comparable between studies and across the Antarctic sea ice zone. We estimate that the Antarctic sea ice zone may contain up to 9 Mmole sulphur as DMSP.

In situ primary production in young Antarctic sea ice

An in situ incubation technique used successfully to measure the photosynthetic carbon assimilation of internal algal assemblages within thick multiyear Arctic ice was developed and improved to measure the photosynthetic carbon assimilation within young sea ice only 50 cm thick (Eastern Weddell Sea, Antarctica). The light transmission was improved by the construction of a cylindrical frame instead of using a transparent acrylic-glass barrel. The new device enabled some of the first precise measurements of in situ photosynthetic carbon assimilation in newly formed Antarctic sea ice, which is an important component in the sea ice ecosystem of the Antarctic Ocean. The rates of carbon assimilation of the interior algal assemblage (top to 5 cm from bottom) was 0.25 mg C m−2 d−1 whereas the bottom algal community (lowest 5 cm) attained only 0.02 mg C m−2 d−1. Chl a specific production rates (PChl) for bottom algae (0.020 – 0.056 μg C μg chl a−1 h−1) revealed strong light limitation, whereas the interior algae (PChl = 0.7 – 1.2 μg C μg chl a−1 h−1) were probably more limited by low temperatures (< –5 °C) and high brine salinities.

Primary production in the upper sea ice

Observations and expenments were conducted on fast ice in McMurdo Sound, Antarctica, to investigate seasonal changes in primary production in the upper sea ice intenor. In November and early December 1995, a dense phytoflagellate assemblage developed in the brine channels and pockets at a snow-free site. Primary production was calculated from I4C measurements of primary productivity in brine samples combined with estimates of the proportion of the ice volume occupied by brine. On 4 December 1995, when the dinoflagellate PolareUa glacialis dominated, eshmated daily production peaked at 12.4 mg C m-' in the upper 50 cm of ice. On this date, brine temperature was --3°C and brine salinity was -60. By mid-December, daily production d e c h e d by 77 %, but chlorophyll-specific rates of photosynthesis remained high. The decline in production coincided with encystment of P. glacialis and nutnent deplehon, the former triggered by the latter. Pnmary production continued to decrease during December and January. On 9 January 1996, when ice temperatures were --1°C and brine salinlty was -20, there was a brief bloom of small pennate diatoms in the upper ice interior, but chlorophyll-specific rates of photosynthesis were low and estimated daily production was < l mg C m-' Based on I4C uptake and brine volume, algal production in the upper 50 cm of sea ice was 181 mg C m-* for the season (mid-November through mid-January). Increases in phytoflagellate biomass in the upper 90 cm of ice for this same period indicated that produchon was 2 5 6 mg C m-'. Bnef early season blooms of cryoand halo-tolerant phytoflagellates accounted for most of the primary production in the upper sea ice interior.

Primary and bacterial production in sea ice in the northern Baltic Sea

The temporal variation of ice primary and bacterial production along with ice algal, bacterial and heterotrophic flagellate biomass were studied at a coastal station in the northern Baltic Sea throughout the ice-covered period of 1996 (January to April). Ice core samples were taken every week and analyzed for abundance and production of different microorganisms. In addition, physical and chemical parameters were measured. The ice algae were Limited by light during the first 3 mo of the study. The algal production showed a peak in the middle of April, which coincided with a marked increase in light availability. Shortly after that, the system became phosphorus depleted and primary production decreased rapidly. Bacterial biomass and production rates were relatively low and stable before the ice algal bloom. After the ice algal bloom, bacterial production increased rapidly, while the biomass remained low. The growth rate of small heterotrophic flagellates (<l0 pm), calculated from increase in biomass, was more than 1 order of magnitude higher than the bacterial production rate following the ice algal bloom. Thus, small heterotrophic flagellates were using food sources other than bacteria for growth after the ice algal bloom. On an annual basis, the ice algal and bacterial production accounted for < l % and <0.1% respectively of the total production (ice + pelagic) due to a short ice-covered season. During the ice-covered season, however, the ice algae accounted tor 10% of the total algal production, whlle ice bacterial production was 0.2 % of the total bacterial produckon.

Determination of Arctic ice algal production with a new in situ incubation technique

A new in situ incubation technique was developed to measure primary production in sea ice. This method allows fine-scale measurements in 1 cm thick vertical sections throughout the ice column without severe disruption of ice morphology, geochemistry and light field. Easy handling in the field makes this device usable for all scientists working on sea ice biota. Primary production within first(FYSI) and multi-year sea-ice (MYSI) cores of the Barents and Greenland Seas was determined during the RV 'Polarstern' cruise ARK XIII/1(a+b). In order to measure algal production, 6 slices of 1 cm thickness were cut off at regular intervals along an ice core and incubated in sealed glass petri dishes. The incubation chambers and a chamber for dark fixation, together with the remaining sections of the ice core, were placed in an acrylic-glass barrel of 1 m length, and returned to their original positions inside the core hole for in situ rate determinations. Additional ice cores were drilled to determine ice temperature and nutrient and algal pigment concentrations. The incident photosynthetically active radiation (PAR) as well as under ice irradiance was measured. Steep gradients in primary production were found throughout the ice floes, with maximum values of 7.7 µg C l-1 h-1 in the bottom few centimetres corresponding to the highest concentrations of chlorophyll a (84 µg l-1). Nutrient concentrations in brine varied between ice stations and with ice depth: 0-88.4 µmol l-1 for NH4; 2.2-13.6 µmol l-1 for NO3; 0-0.5 µmol l-1 for NO2; 0-12.4 µmol l-1 for PO4; and 0.2-23.5 µmol l-1 for SiO4. Mean integrated production at the 4 stations (0.76-9.67 mg C m-2 d-1) varied with PAR and total dissolved nitrogen. Integrated production of the ice interior community (more than 5 cm from bottom of floe) was in the same range as or sometimes exceeded production in the bottom community (0-5 cm) of FYSI as well as MYSI. Growth rates of the ice algae ranged from 0.01 to 0.5 d-1. As previous primary production methods were restricted to the study of bottom communities only, we assert that algal primary production in Arctic as well as Antarctic sea ice has been severely underestimated.

Primary production of the northern Barents Sea

The majority of the arctic waters are only seasonally ice covered; the northern Barents Sea, where freezing starts at 80 to 81°N in September, is one such area. In March, the ice cover reaches its greatest extension (74-75°N). Melting is particularly rapid in June and July, and by August the Barents Sea may be ice free. The pelagic productive season is rather short, 3 to 3.5 months in the northern part of the Barents Sea (north of the Polar Front, 75°N), and is able to sustain an open water production during only half of this time when a substantial part of the area is free of ice. Ice algal production starts in March and terminates during the rapid melting season in June and July, thus equalling the pelagic production season in duration. This paper presents the first in situ measurements of both pelagic and ice-related production in the northern Barents Sea: pelagic production in summer after melting has started and more open water has become accessible, and ice production in spring before the ice cover melts. Judged by the developmental stage of the plankton populations, the northern Barents Sea consists of several sub-areas with different phytoplankton situations. Estimates of both daily and annual carbon production have been based on in situ measurements. Although there are few sampling stations (6 phytoplankton stations and 8 ice-algae stations), the measurements represent both pelagic bloom and non-bloom conditions and ice algal day and night production. The annual production in ice was estimated to 5.3 g Cm-2, compared to the pelagic production of 25 to 30 g Cm-2 south of Kvitoya and 12 to 15 g Cm-2 further north. According to these estimates ice production thus constitutes 16% to 22% of the total primary production of the northern Barents Sea, depending on the extent of ice-free areas.

Distribution, abundance and biology of ringed seals (&lt;i&gt;Phoca hispida&lt;/i&gt;): an overview

The ringed seal (Phoca hispida) has a circumpolar Arctic distribution. Because of its great importance to northern communities and its role as the primary food of polar bears (Ursus maritimus) the ringed seal has been studied extensively in Canada, Alaska, Russia, Svalbard and Greenland as well as in the Baltic Sea and Karelian lakes. No clear-cut boundaries are known to separate ringed seal stocks in marine waters. Adult seals are thought to be relatively sedentary, but sub-adults sometimes disperse over long distances. Stable ice with good snow cover is considered the most productive habitat although production in pack ice has been little studied. Populations appear to be structured so that immature animals and young adults are consigned to sub-optimal habitat during the spring pupping and breeding season. Annual production in ringed seal populations, defined as thepup percentage in the total population after the late winter pupping season, is probably in the order of 18-24%. Most estimates of maximum sustainable yield are in the order of 7%.The world population of ringed seals is at least a few million. Methods of abundance estimation have included aerial surveys, dog searches and remote sensing of lairs and breathing holes, acoustic monitoring, correlation analysis by reference to sizes of polar bear populations, and inference from estimated energy requirements of bear populations. Aerial strip survey has been the method of choice for estimating seal densities over large areas. Adjustment factors to account for seals not hauled out at the time of the survey, for seals that dove ahead of the aircraft, and for seals on the ice within the surveyed strip but not detected by the observers, are required for estimates of absolute abundance.Male and female ringed seals are sexually mature by 5-7 years of age (earlier at Svalbard). Pupping usually occurs in March or early April and is followed by 5-7 weeks of lactation. Breeding takes place in mid to late May, and implantation is delayed for about 3 months. In at least some parts of their range, ringed seals feed mainly on schooling gadids from late autumn through early spring andon benthic crustaceans and polar cod (Boreogadus saida) from late spring through summer. Little feeding is done during the moult, which takes place in late spring and early summer. Pelagic crustaceans offshore and mysids inshore become important prey in late summer and early autumn in some areas. Ringed seals have several natural predators, the most important of which is the polar bear in most arctic regions. Arctic foxes (Alopex lagopus) kill a large percentage of pups in someareas.From a conservation perspective, the ringed seal appears to be secure. Levels of exploitation of arctic populations have usually been considered sustainable, except in the Okhotsk Sea. Large fluctuations in production of ringed seals in the Beaufort Sea and Amundsen Gulf are thought to be driven by natural variability in environmental conditions. While concern has been expressed about thepotential impacts of industrial activity and pollution on ringed seals, such impacts have been documented only in limited areas. Because of their ubiquitous occurrence and availability for sampling, ringed seals are good subjects for monitoring contaminant trends in Arctic marine food chains.

Primary production of the northern Barents Sea

The majority of the arctic waters are only seasonally ice covered; the northern Barents Sea, where freezing starts at 80 to 81°N in September, is one such area. In March, the ice cover reaches its greatest extension (74-75°N). Melting is particularly rapid in June and July, and by August the Barents Sea may be ice free. The pelagic productive season is rather short, 3 to 3.5 months in the northern part of the Barents Sea (north of the Polar Front, 75°N), and is able to sustain an open water production during only half of this time when a substantial part of the area is free of ice. Ice algal production starts in March and terminates during the rapid melting season in June and July, thus equalling the pelagic production season in duration. This paper presents the first in situ measurements of both pelagic and ice-related production in the northern Barents Sea: pelagic production in summer after melting has started and more open water has become accessible, and ice production in spring before the ice cover melts. Judged by the developmental stage of the plankton populations, the northern Barents Sea consists of several sub-areas with different phytoplankton situations. Estimates of both daily and annual carbon production have been based on in situ measurements. Although there are few sampling stations (6 phytoplankton stations and 8 ice-algae stations), the measurements represent both pelagic bloom and non-bloom conditions and ice algal day and night production. The annual production in ice was estimated to 5.3 g Cm-2, compared to the pelagic production of 25 to 30 g Cm-2 south of Kvitøya and 12 to 15 g Cm-2 further north. According to these estimates ice production thus constitutes 16% to 22% of the total primary production of the northern Barents Sea, depending on the extent of ice-free areas.

Measurements of in situ 14C concentrations in Greenland Ice Sheet Project 2 ice covering a 17‐kyr time span: Implications to ice flow dynamics

We present results of measurements of 14C in CO and CO2 phases for selected Greenland Ice Sheet Project 2 firn and ice samples up to a depth of 1838 m (16.6 kyr B.P.). The results show that 14C in ice consists of both in situ‐produced cosmogenic 14C, which can be either in the form of CO or CO2, and trapped atmospheric 14CO2. In agreement with our previous work on studies of 14C concentrations in Antarctic firn and ice samples and some GISP2 samples, we found that the cosmogenic in situ‐produced 14C (from spallation of oxygen nuclei) is greater than the trapped atmospheric 14C component. Also, we can show the total 14C amounts in ice are consistent with an efficient retention of the in situ variety of 14C in older ice where we expect lower average temperatures at the time of formation. The firn samples appear to have lost much of the 14C, probably during storage. The ice accumulation rates are estimated after due corrections for the CO2 content of trapped air and “secondary” 14C production in ice during storage at altitude. These values are in good accord with the recent model estimates of Cutler et al. [1995], except for two samples, at depths 1518.5 m (9740 years B.P.) and 1698.5 m (12,360 years B.P.). In the first case, the in situ 14C concentration is significantly higher than that predicted by either of the models, by a factor of about 2. In the second case, the estimate of Cutler et al. [1995] is a ∼ 50% lower accumulation rate, but the 14C result is consistent with adjacent samples. A possible reason for the first discrepancy may be the decreased atmospheric pressure at that time at the site, as suggested by D. Raynaud et al. (unpublished manuscript, 1995).

Primary Production in Antarctic Sea Ice

A numerical model shows that in Antarctic sea ice, increased flooding in regions with thick snow cover enhances primary production in the infiltration (surface) layer. Productivity in the freeboard (sea level) layer is also determined by sea ice porosity, which varies with temperature. Spatial and temporal variation in snow thickness and the proportion of first-year ice thus determine regional differences in sea ice primary production. Model results show that of the 40 teragrams of carbon produced annually in the Antarctic ice pack, 75 percent was associated with first-year ice and nearly 50 percent was produced in the Weddell Sea.

DOC and its relationship to algae in bottom ice communities

The seasonal development of algal biomass and dissolved organic carbon (DOC) in bottom ice was determined for two widely separated areas of annual sea ice, Saroma-ko in northern Japan and Resolute Passage in the Canadian High Arctic, to determine the importance of DOC to estimates of primary production in sea ice communities. As algal biomass, measured either as chlorophyll a (Chl a) or particulate organic carbon (POC), increased, DOC concentrations increased to extremely high values (up to 40 mg Cl−1 DOC). The highest algal biomass and DOC concentrations were observed at Resolute under thin (4–8 cm) snow cover. Highly significant double-log linear relationships (r2 = 62–80%, p < 0.01) existed between DOC and both Chl a and POC, suggesting much of the DOC originated from the ice algae. A highly significant global relationship between DOC and POC (r2 = 74%, p<0.01) was also found when previously published data for Frobisher Bay were included, indicating substantial consistency in the relationship between DOC and algal biomass among widely separated locations and differing climatic/hydrodynamic regimes. The significance of the apparently rich production of substrates for microheterotrophic processes in the ice is unclear until the nature and origin of the DOC are better resolved. It is clear, however, that estimates of organic production in ice based only on accumulation of particulate organic material will be seriously biased if dissolved material is ignored.

Open water production in Arctic sea ice: Satellite measurements and model parameterizations

Sequential synthetic aperture radar (SAR) images from the ERS 1 spacecraft were routinely used as input to the Geophysical Processor System at the Alaska SAR Facility from 1992 through 1994 to produce sea ice displacement vectors on a 5‐km grid. We have combined some 5000 of these products, consisting of nearly 700,000 displacement vectors, into a set of 914 strips or mosaics of ice motion that span (mostly) 3‐day intervals. For each strip we compute the opening and closing of leads based on the change in area of the 5‐km grid cells. We also compute the area‐averaged deformation or strain invariants of the motion. The small‐scale (several kilometer) lead activity can be parameterized fairly well in terms of the large‐scale (several hundred kilometer) strain invariants. Sea ice models implicitly contain such a parameterization through their constitutive equations. The well‐known model of Hibler (1979) that uses a viscous‐plastic rheology and an elliptical yield curve is in good agreement with our data. The variance in the data about this theoretical relationship is less than that suggested by a random model of sea ice motion. The data also indicate that shearing deformation contributes to the opening and closing of leads. Models with two categories or levels of ice thickness generally do not take shearing deformation into account in the evolution of the ice concentration, nor do they redistribute ice as a result of ridging. We show how to add these features to two‐level models. However, we argue that three‐level models consisting of open water, thin ice, and thick ice are much better suited to the proper treatment of open water production, and we present such a model.

Gross and net primary production in the Scotia-Weddell Sea sector of the Southern Ocean during spring 1988

Daily rates of gross and net primary production were calculated in the Scotia-Weddell Sea sector of the Southern Ocean during spring 1988 (EPOS, Leg 2) on the basis of kinetic experiments, which combine radiotracer technology and classic biochemical procedures, and by taking into account the light regime, the physical structure of the water column, the vertical distribution of chlorophyll a, and the protozoan grazing pressure. From these calculations, three distinct sub-areas were identified: the Closed Pack Ice Zone (CPIZ), characterized by the lowest average gross primary production (0.36 gC · m−2 · day−1); the Marginal Ice Zone (MIZ) with a maximum mean value of 1.76 gC · m−2 · day−1; and the Open Ocean Zone off the ice edge (OOZ) with an intermediate mean value of 0.87 gC · m−2 · day−1. Net primary production fluctuated nearly in the same proportions, averaging 0.55, 0.2 and 1.13 gC · m−2 · day−1 in the OOZ, CPIZ and MIZ respectively, representing 53% of the total photo-assimilated carbon under heavy ice cover (CPIZ) and 64% in the two other areas. Available light, strongly dependent on the ice cover, was shown to control the level of primary production in the sea ice associated sub-areas, whilst protozoa grazing on phytoplankton determined the moderate primary production level characteristic of the “well illuminated” OOZ area.