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Babaluk, J. A. et al. Evidence for non-anadromous behaviour of arctic charr ( Salvelinus alpinus) from Lake Hazen, Ellesmere Island, northwest Territories, Canada, based on scanning proton microprobe analysis of otolith strontium distribution. Arctic 50, 224–233 (1997). Sanchez-Cabeza, J. A. & Ruiz-Fernandez, A. C. Pb-210 sediment radiochronology: an integrated formulation and classification of dating models. Geochim. Cosmochim. Acta 82, 183–200 (2012).

A mass budget model that determines glacier surface melt using the temperature-index method was used to estimate glacial runoff volume into Lake Hazen. The model was forced with downscaled and bias-corrected temperature and precipitation fields from the National Centers for Environmental Prediction/National Center for Atmospheric Research Reanalysis. The model and its validations are detailed in the Supplementary Methods of Gardner et al. 20, with the exception that for this study it was configured to provide output at a daily resolution. Results presented here are the average of three model realizations that produce results that closely match the average of the 1000 model realizations reported in Gardner et al. 20. The model was additionally validated against the only known in situ surface mass balance measurements collected for any glacier (Gilman Glacier) within the Lake Hazen watershed. Model results agree exceptionally well with the 4 years of in situ observations collected between 1958 and 1962 40 (Supplementary Fig. 6). Lake Hazen water levels and outlet discharge Paleoecological Environmental Assessment and Research Lab, Department of Biology, Queen’s University, Kingston, ON, K7L 3N6, Canada Koerner, R. M. in Satellite Image Atlas of Glaciers of the World (eds Williams, R. S. & Ferrigno, J. G.) J111–J146 (U.S. Geological Survey, 2002). Heathcote, A. J., Anderson, N. J., Prairie, Y. T., Engstrom, D. R. & del Giorgio, P. A. Large increases in carbon burial in northern lakes during the Anthropocene. Nat. Commun. 6, 10016 (2015). Perren, B. B. et al. Twentieth-century warming revives the world’s northernmost lake. Geology 40, 1003–1006 (2012).Freeze-dried sediments, washed with dilute HCl to remove carbonate, were analyzed for δ 13C, δ 15N, %N and %C with a Delta Plus (Thermo) continuous flow isotope ratio mass spectrometer coupled to a Carlo Erba 1500 Elemental Analyzer in the Environmental Geochemistry and Environmental Isotope laboratories, University of Waterloo. The δ 15N and δ 13C ratios (‰) were determined using the equation δ R‰ = (( R sample = R standard) − 1) × 1000, where R sample was the ratio of 15N/ 14N or 13C/ 12C in the sample, and R standard for 13C or 15N was referenced to that in Vienna Pee Dee Belemnite and atmospheric air, respectively. Precision of analysis was 0.2 and 0.3‰ for δ 13C and δ 15N, and 0.3% and 0.03% for %C and %N. Elsewhere there was gold for the England men’s 4x100m team of Jona Efoloko, Zharnel Hughes, Nethaneel Mitchell-Blake and Ojie Edoburun, whose time of 38.35sec saw off Trinidad & Tobago and Nigeria, despite a minor baton hiccup due to the noise from the 30,000 crowd. A few minutes later, England’s Asha Philip, Imani-Lara Lansiquot, Bianca Williams and Daryll Neita won silver in a tougher contest, running 42.41 behind Nigeria, with Jamaica taking third. The result was special for Williams, who was joined on her lap of honour by her two-year-old son Zuri. “That is the first time he has been out on a big stage but there will be many more,” she said. Taylor, K. E., Stouffer, R. J. & Meehl, G. A. An overview of CMIP5 and the experiment design. Bull. Am. Meteorol. Soc. 93, 485–498 (2012).

Bolger, T. & Connolly, P. L. The selection of suitable indexes for the measurement and analysis of fish condition. J. Fish. Biol. 34, 171–182 (1989). Ohuruogu, the younger sister of the Olympic and world champion Christine, was delighted to win the first major medal of her career after a few years in the wilderness. “It took me quite a few years to get over the pressure of my sister and I don’t know if it’s too late but now I am coming into my own,” said the 29-year-old, who set a personal best of 50.72 to take the silver medal.Muir, D. C. G. et al. Spatial trends and historical deposition of mercury in Eastern and Northern Canada inferred from lake sediment cores. Environ. Sci. Technol. 43, 4802–4809 (2009). There was more medal success for Scotland in the women’s 5,000m as Eilish McColgan produced a performance of grit and substance to come second behind the world silver medallist Beatrice Chebet of Kenya. Organochlorine pesticides and related compounds (OCPs) were determined by ALS Environmental, Burlington, ON ( www.alsglobal.com) in select sediment sample intervals using USEPA Method 1699. In brief, wet sediments were mixed with anhydrous Na 2SO 4 to give a free-flowing mixture. Percent moisture was determined separately on samples analyzed for multi-elements to allow for results to be expressed on a dry weight basis. Laboratory blanks consisting of all lab reagents were run with each batch of 12 samples. The 13C 12-PCB-133 was added prior to extraction as an internal standard. The Na 2SO 4 solid mixture was Soxhlet extracted overnight with dichloromethane. The extract was spiked with a suite of 13C-labeled OCPs prior to instrumental analysis for target quantification. The raw extracts were cleaned by gel permeation chromatography to remove pigment co-extractives and then subjected to a silica gel column cleanup. The OCPs were analyzed by gas chromatography-high-resolution mass spectrometry (mass resolution >8000) and quantified relative to 13C-OCPs via isotope dilution. All data were recovery corrected for extraction losses relative to 13C 12-PCB-133 responses. Sediment SRM NIST 1941b was analyzed with each batch of 12 samples. Results for certified OCP analytes were within ±20% of certified values. The OPCs reported here include alpha-, beta- and gamma-HCH, heptachlor, aldrin heptachlor epoxide B, oxychlordane trans- and cis-chlordane, trans-nonachlor, dieldrin, endrin cis-nonachlor, alpha- and beta-endosulfan, endosulfan sulfate, 2,4′- and 4,4′-DDE, 2,4′- and 4,4′-DDD, 24′- and 4,4′-DDT, methoxychlor, mirex, and Parlar-26, -50 and -62. Siliceous microfossil identification and abundance counts This 1500m, though, was far weaker than Muir is used to facing. The first two laps were run in a dawdling 2min 15sec, allowing her to ease towards the front before striking for glory with 500m remaining.

The California redwoods are truly more majestic than I could ever convey, and something that every resident and visitor should see at least once. If you ever find yourself in my beautiful Golden State, do not leave without seeking them out. Smol, J. P. & Douglas, M. S. V. Crossing the final ecological threshold in high Arctic ponds. Proc. Natl. Acad. Sci. USA 104, 12395–12397 (2007).

Perry, E., Norton, S. A., Kamman, N. C., Lorey, P. M. & Driscoll, C. T. Deconstruction of historic mercury accumulation in lake sediments, Northeastern United States. Ecotoxicology 14, 85–99 (2005). Antoniades, D. et al. Abrupt environmental change in Canada’s northernmost lake inferred from fossil diatom and pigment stratigraphy. Geophys. Res. Lett. 34, L18708 (2007). Lake Hazen Arctic Char condition was calculated from morphometric measures made on Arctic Char collected in 1981, 1990, 1992, 1995, 1996, 1998 and 2001 47, as well as on Arctic Char subsequently collected in 2003 ( N = 17), 2006 ( N = 22), 2007 ( N = 18), 2008 ( N = 15), 2010 ( N = 25) and 2014 ( N = 19) 48, 49, 50. Fulton’s condition factor (CF = 100 × weight [g]/fork length 3 [cm 3]) 51 was calculated for all Arctic Char >200 g. Data availability