Described fully in (https://doi.org/10.21203/rs.3.rs-636839/v1 holder). Data The main CEL method, and a subsidiary Coastal Exposure Index or CEI (both described below), are based on daily sea-ice concentration products for the period 1979 through 2020. These products are derived from the multi-satellite passive-microwave brightness temperature time series using the NASA Team algorithm, mapped at 25 km x 25 km resolution and obtained from the NASA National Snow and Ice Data Center (NSIDC) Distributed Active Archive Center (DAAC). Both algorithms are designed to be adaptable for different resolution data. Complete coverage of the entire Antarctic coastal and sea-ice zones is obtained on a daily basis, except for 1979-July 1987 (once every two days). Missing single days during this period are interpolated from the adjoining day's sea-ice concentration values. Averages and climatologies are based on the period 1979-2020, unless otherwise stated. The continental land mask used (gsfc_25s.msk) is also obtained from NSIDC, and includes ice shelves (the seaward extremities of which are taken here to be coastline). Coastline grid points are defined from the continental land mask as any ocean grid point that has land/ice sheet adjacent to it. Analysis methods For this study, we developed two new but different algorithms for quantifying and monitoring Antarctic coastal exposure: the Coastal Exposure Index (CEI) and Coastal Exposure Length (CEL) method. The CEI technique is based on the detection of sea ice presence/absence radially out (northwards) from the coastline along each meridian (at one degree longitudinal spacing), following masking of the ice sheet. The CEI is simply defined as the number of longitudes with no sea ice (threshold set to less than 15% following convention) to the north of the continent, and hence runs from zero to 360. This methodology is trivial and code for this is not included. CEL is defined as the length (in kms) of the Antarctic coastal perimeter with no adjacent sea ice anywhere offshore (i.e. total exposure of the coast to the open Southern Ocean with no intervening sea ice), but excluding coastal polynyas. By this method, we use the land mask to determine if each coastal grid point has an immediately-adjacent ocean grid point that is ice-free (i.e. has a sea-ice concentration of less than 15%). If this criterion is met, then a nearest (adjoining) neighbour-testing technique is used to determine whether that ocean grid point is exposed in some way to the wider open ocean or is bound by neighbouring sea ice offshore. If any of the neighbouring grid points are classified as “exposed”, or if the total area of neighbouring ice-free grid points exceeds an arbitrary cut-off of 500,000 km2, then that coastal grid point is classified as “exposed”. Otherwise, the grid point and all sea-ice-free neighbouring grid points are deemed to be bounded by sea ice and are classified as a coastal polynya. The length of individual exposed coastal grid points is estimated by taking the square root of the respective pixel area. The length of coastal exposure, either regionally or net circum-Antarctic, is then simply the sum of the length of exposed coastal grid points. The IDL code used for calculating CEL is included here.

The Davis Aerodrome Project (DAP) collected a range of environmental survey data over several field seasons to support a comprehensive environmental assessment of the proposed aerodrome. This data includes flora, fauna, soils, lake ecosystem, nearshore, marine, air quality and meteorological information which has been collected by a number of different methods, and extends across the current Davis Station, proposed aerodrome and supporting infrastructure footprint (Ridge Site), previous sites considered for the aerodrome (Heidemann Valley, Adams Flat), as well as locations across the Vestfold Hills away from any of the proposed developments.(this text is standard for all DAP datasets being added to the AADC). This dataset contains short-term nearshore marine current profile data collected to inform environmental assessment processes related to the Australian Antarctic Division’s DAP and Davis Masterplan projects. Eight current meter deployments were undertaken across six sites in the nearshore marine environment in the vicinity of Davis Research station. Deployment periods ranged from three days (3 x 24hr tide cycle) to two weeks. Sites were selected based on the location of previous sampling activity (CM1-5) and sites of interest to Davis Aerodrome and Davis Masterplan projects with regard to proposed future developments in the area. A second deployment was undertaken at two key sites to increase the sampling interval at each. Data was collected using a Nortec Aquadopp Profiler 1 MHz. The same instrument was used to collect current profiles at all sites. The instrument was deployed through a 40cm hole drilled through the seaice. It was suspended horizontally in the water column (mid-way between the seafloor and the under surface of the ice) by a bridal attachment and rope secured at the surface (see figure below). A 15cm fin was attached to the base of the instrument for all deployments. In shallow locations the instrument was positioned so that it could not hit the seafloor throughout the lowest tidal cycle during the deployment. The profile interval was set to record every 900 seconds (15min) for a period of 120 seconds (2min). All instrument settings and recording details are contained in the hdr files saved in each data folder. Start and end dates and times are set out in the “current meter deployment details” spreadsheet. Temporal coverage Site No. Deployment Date Retrieval Date CM1 22/10/2021 2/22/2021 CM2 16/09/2021 19/09/2021 CM2 9/10/2021 22/10/2021 CM3 3/11/2021 12/11/2021 CM5 24/11/2021 4/11/2021 ML 8/12/2021 14/12/2021 OptionA 29/09/2021 2/10/2021 OptionA 14/12/2021 20/12/2021 Spatial coverage CM2_01_20210919 68.57399536 77.96031373 OptionA_01_20211002 68.57597253 77.96121253 CM2_02_20211022 68.57399536 77.96031373 CM1_01_20211102 68.57749077 77.95758156 CM3_01_20211112 68.57276237 77.94873464 CM5_01_20211204 68.58321738 77.9180513 ML_01_20211214 -68.58381482 77.94507546 OptionA_02_20211220 68.57585945 77.96151685

Untreated, macerated wastewater effluent has been discharged to the sea at Davis Station since 2005, when the old wastewater treatment infrastructure was removed. This environmental assessment was instigated to guide the choice of the most suitable wastewater treatment facility at Davis. The assessment will support decisions that enable Australia to meet the standards set for the discharge of wastewaters in Antarctica in national legislation (Waste Management Regulations of the Antarctic Treaty Environmental Protection Act - ATEP) and to meet international commitments (the Madrid Protocol) and to meet Australia's aspirations to be a leader in Antarctic environmental protection. The overall objective was to provide environmental information in support of an operational infrastructure project to upgrade wastewater treatment at Davis. This information is required to ensure that the upgrade satisfies national legislation (ATEP/Waste Management Regulations), international commitments (the Madrid Protocol) and maintain the AAD's status as an international leader in environmental management. The specific objectives were to: 1. Wastewater properties: Determine the properties of discharged wastewater (contaminant levels, toxicity, microbiological hazards) as the basis for recommendations on the required level of treatment and provide further consideration of what might constitute adequate dilution and dispersal for discharge to the nearshore marine environment 2. Dispersal and dilution characteristics of marine environment: Assess the dispersing characteristics of the immediate nearshore marine environment in the vicinity of Davis Station to determine whether conditions at the existing site of effluent discharge are adequate to meet the ATEP requirement of initial dilution and rapid dispersal. 3. Environmental impacts: Describe the nature and extent of impacts to the marine environment associated with present wastewater discharge practices at Davis and determine whether wastewater discharge practices have adversely affected the local environment. 4. Evaluate treatment options: Evaluate the different levels of treatment required to mitigate and/or prevent various environmental impacts and reduce environmental risks.