Chlorophyll‐a in Antarctic Landfast Sea Ice: A First Synthesis of Historical Ice Core Data

Abstract

Historical sea ice core chlorophyll‐a (Chla) data are used to describe the seasonal, regional, and vertical distribution of ice algal biomass in Antarctic landfast sea ice. The analyses are based on the Antarctic Fast Ice Algae Chlorophyll‐a data set, a compilation of currently available sea ice Chla data from landfast sea ice cores collected at circum‐Antarctic nearshore locations between 1970 and 2015. Ice cores were typically sampled from thermodynamically grown first‐year ice and have thin snow depths (mean = 0.052 ± 0.097 m). The data set comprises 888 ice cores, including 404 full vertical profile cores. Integrated ice algal Chla biomass (range: <0.1–219.9 mg/m2, median = 4.4 mg/m2, interquartile range = 9.9 mg/m2) peaks in late spring and shows elevated levels in autumn. The seasonal Chla development is consistent with the current understanding of physical drivers of ice algal biomass, including the seasonal cycle of irradiance and surface temperatures driving landfast sea ice growth and melt. Landfast ice regions with reported platelet ice formation show maximum ice algal biomass. Ice algal communities in the lowermost third of the ice cores dominate integrated Chla concentrations during most of the year, but internal and surface communities are important, particularly in winter. Through comparison of biomass estimates based on different sea ice sampling strategies, that is, analysis of full cores versus bottom‐ice section sampling, we identify biases in common sampling approaches and provide recommendations for future survey programs: for example, the need to sample fast ice over its entire thickness and to measure auxiliary physicochemical parameters.

Patterns and drivers of carbohydrate budgets in ice algal assemblages from first year Arctic sea ice

“…Local drivers such as salinity, snow cover and ice thickness are key factors regulating ice algal patchiness at different scales (Gosselin et al ; Granskog et al ; Campbell et al ). Ice thickness has been found to be a good general predictor of ice Chl a and dissolved carbohydrate content at large geographical scales (Meiners et al ; Underwood et al ), and was a driver for increased relative contribution of pCHO HW and pCHO HB in this study (Fig. ).…”

“…The many roles of sea ice carbohydrates are pertinent at local and regional scales. The existence of relationships between sea ice physical properties, ice algae Chl a and dissolved carbohydrate concentrations (Meiners et al ; Underwood et al ), coupled with the characterisation of the complete sea ice carbohydrate budget reported here, provide a basis for modelling sea ice CHO TOTAL at regional scales. Understanding the production and composition of sea ice carbohydrates under future sea ice conditions, and their fate as they are released into the water column, is an important area of future work to understand changes in carbon cycling and microbial activity in the context of rapidly changing Arctic seas.…”

Estimation of Antarctic Land‐Fast Sea Ice Algal Biomass and Snow Thickness From Under‐Ice Radiance Spectra in Two Contrasting Areas

“…Specifically, our results are applicable for Antarctic fast ice which comprises mainly ice algal bottom communities. The NDI algorithms developed in Melbourne‐Thomas et al () and Lange et al () have already shown the applicability of the NDI technique for pack ice environments which can comprise not only the bottom communities but also ice algal interior and surface communities (e.g., Meiners et al, ). However, in general chl a concentrations in these studies were low compared to the current study.…”

Dependency of Antarctic zooplankton species on ice algae‐produced carbon suggests a sea ice‐driven pelagic ecosystem during winter

“…Conversely, Antarctic bottom ice algal Chlorophyll a concentrations are higher by about one order of magnitude. Typically, ice algal Chlorophyll a concentrations are in the order of 2–4 mg/m 3 (Meiners et al, ). During our study, they reached mean values of 22 and 12 mg/m 3 at ice camp 1 and ice camp 2, respectively (Meyer et al, ).…”