Late winter biogeochemical conditions under sea ice in the Canadian High Arctic

Figures & data

Fig. 1  Bathymetric maps showing the Arctic Ocean. The Catlin Arctic Survey ice base (CIB) is marked with a red dot (78°N, 104°W) on map (a). The Catlin Arctic Survey expedition transect sampling locations are marked with red dots on map (b) between 85°N to 90°N. (c) An enlarged map of Deer Bay overlaid with a satellite image from 8 February 2010, also showing the location of the CIB marked by a red dot.

Table 1 Ice core collection data, size of each section (top, middle and bottom), total core length and snow cover.

	Ice core
	1	2	3	4
Collection date	08/04/10	08/04/10	13/04/10	13/04/10
Top (cm)	0–54	0–56	0–62	0–52
Mid (cm)	54–118	56–112	62–121	52–104
Bottom (cm)	118–172	112–170	121–177	104–163
Total length (cm)	172	170	177	163
Snow cover (cm)	4.5	2	5	3

Fig. 2  Wind speed (m s⁻¹) and air temperature (°C) measured at the Catlin Ice Base (CIB) during March and April 2010.

Fig. 3  Under the sea-ice water column profiles through the field campaign from 17 March to 26 April 2010 (different colours represent the different sample dates) for (a) 0 to 50 m temperature, (b) 0 to 50 m salinity, (c) 0 to 220 m temperature and (d) 0 to 220 m salinity. (e) Potential temperature versus salinity plots, overlaid with isopycnals, for all data from the full depth profiles, also highlighting every 50 m depth. (f) Nitrate versus phosphate concentrations (mean±1 SD) for each depth over the field campaign, also showing the PO₄ versus NO₃ regression lines expected for Atlantic Water (AW) and Pacific Water (PW; from Jones et al. 1998).

Fig. 4  (a) Uncalibrated acoustical backscatter intensity data from the 300-kHz acoustic doppler current profiler deployed for three days beneath the ice; (b) current speeds from the same instrument, showing significant variability and vertical shear, overlying lines indicate tidal elevation from the Webtide model (solid blue line) and current speeds averaged over the top 45 m and over 15 min (solid red line); and (c) current direction from the same instrument (degrees).

Fig. 5  (a–d) Average (mean) surface conditions (1 to 10 m of seawater) through the sampling period for (a) nitrate (µM), ammonium (µM) and chlorophyll (mg m⁻³), (b) phosphate (µM) and silicate (µM), (c) total inorganic carbon (C_T, µmol kg⁻¹) and total alkalinity (A_T, µmol kg⁻¹) and (d) seawater pCO₂ (pCO₂sw), atmospheric pCO₂ (pCO₂atm) measured at the ice base by the eddy covariance system and pCO₂ from the Alert weather station (pCO₂atm Alert, [Dlugokencky et al. 2015]). (e–l) Average depth profiles for (e) nitrate, (f) phosphate, (g) silicate, (h) ammonium, (i) total inorganic carbon concentration (C_T), (j) total alkalinity (A_T), (k) pH_T and (l) aragonite saturation state (aragonite Ω). The error bars represent ±1 standard deviation.

Table 2 Biogeochemical measurements averaged across all ice cores for each section (top, middle and bottom). Values are mean±standard deviation.

	Top section	Middle section	Bottom section
Sal.	8.8±1.1	5.68±0.7	5.19±0.8
Nitrite (µM)	0.06±0.01	0.05±0.02	0.03±0.01
Nitrate (µM)	1.15±0.34	0.40±0.15	0.32±0.14
Phosphate (µM)	0.11±0.03	0.11±0.04	0.19±0.13
Silicate (µM)	1.35±0.20	1.05±0.35	1.26±0.21
Ammonium (µM)	0.61±0.08	0.56±0.16	0.52±0.32
Chl (mg m^−3)	0.21±0.13	0.32±0.28	2.21±0.911
AT (µmol kg^−1)	569±62	402.3±54.75	369.3±56.29
CT (µmol kg^−1)	508±40	374.7±44.05	325.2±51.05

Table 3 Data from CO₂ eddy covariance system. Median values±standard error. Positive values for fluxes of sensible heat/CO₂ indicate transport of heat/CO₂ away from surface into the atmosphere

Date	Air temp. (°C)	V.P.^a (kPa)	W.S.^b (m.s^−1)	CO2 ^c (ppm)	S.H.F.^d (W.m^−2)	CO2 flux (µmol.m^−2.s^−1)
25/04/10	−11.6±0.16	1.09±0.011	5.80±0.08	394.0±0.27	−16.4±1.47	0.0021±0.0467
27/04/10	−8.3±0.17	1.28±0.010	3.88±0.16	392.5±0.21	0.7±0.64	0.0006±0.0307
28/04/10	−16.2±0.33	1.03±0.011	4.36±0.22	392.2±0.21	1.1±0.77	−0.0144±0.0198

^aVapour pressure. ^bWind speed. ^cAtmospheric CO₂ concentration. ^dSensible heat flux.

Fig. 6  Water column profiles at each latitude (shown as different colours) from the Catlin Explorer Transect for (a) salinity and (b) temperature; (c) potential temperature vs salinity plot for the upper 50 m, overlaid with isopycnals. Each figure also shows the upper 50 m Catlin Ice Base data as a comparison (light blue, 78°N). (d) Nitrate versus phosphate concentrations (mean±1 SD) for surface (0 – 10 m) over the transect, also showing the PO₄ vs NO₃ regression lines expected for Atlantic Water (AW) and Pacific Water (PW; from Jones et al. 1998).

Fig. 7  Average (mean±1 SD) surface (0 to 10 m) seawater conditions under the sea ice along the Catlin Explorer Transect from 85°N to the North Pole for (a) salinity and temperature (°C); (b) chlorophyll (mg m⁻³), ammonium (µM) and nitrate (µM); (c) total inorganic carbon (C_T, µmol kg⁻¹) and total alkalinity (A_T, µmol kg⁻¹); (d) phosphate and silicate (µM); (e) pH (total scale) and aragonite saturation state (aragonite Ω) and (f) pCO₂ of seawater, also showing the average atmospheric pCO₂ measured at Alert Station over the duration of the transect (pCO₂atm Alert [Dlugokencky et al. 2015]).

Table 4 Catlin Explorer Transect sample information: date, location (latitude and longitude), snow thickness and ice thickness.

Station	Date	Latitude	Longitude	Snow (cm)	Ice thickness (cm)
1	14/03/10	85°32′54″N	77°44′17″W	19.8	221.0
2	18/03/10	85°38′46″N	77°55′19″W	9.4	259.0
3	21/03/10	85°34′52″N	78°21′14″W	8.2	156.0
4	24/03/10	86°35′77″N	85°00′48″W	2.7	233.0
5	27/03/10	85°49′17″N	79°08′20″W	12.5	300.0
6	30/03/10	86°06′11″N	82°27′01″W	9.0	125.0
7	04/04/10	86°20′47″N	83°42′47″W	14.0	220.5
8	07/04/10	86°35′27″N	85°16′32″W	14.3	272.3
9	10/04/10	86°43′37″N	85°09′29″W	16.3	229.3
10	13/04/10	87°02′07″N	79°34′38″W	56.0	315.7
11	16/04/10	87°25′12″N	71°51′46″W	16.0	373.5
12	20/04/10	87°40′59″N	74°15′15″W	16.0	194.0
13	25/04/10	89°01′36″N	63°14′11″W	24.4	212.4
14	28/04/10	88°22′41″N	59°37′21″W	21.0	198.0
15	01/05/10	88°38′10″N	62°19′33″W	24.7	193.3
16	04/05/10	89°01′52″N	68°10′58″W	29.0	275.7
17	07/05/10	89°22′39″N	72°48′42″W	23.7	225.3
18	12/05/10	90°N		24.0	214.0

Dlugokencky E.J., Lang P.M., Masarie K.A., Crotwell A.M., Crotwell M.J. Atmospheric carbon dioxide dry air mole fractions from the NOAA ESRL Carbon Cycle Cooperative Global Air Sampling Network, 1968–2014. Version 2015-08-03. Boulder, CO: Earth System Research Laboratory, National Oceanic and Atmospheric Administration. 2015. Accessed on the internet at ftp://aftp.cmdl.noaa.gov/data/trace_gases/co2/flask/surface/ [Copyeditor: this does not require an internet access date].

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