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Abrupt Common Era hydroclimate shifts drive west Greenland ice cap change


Ice core archives are well suited for reconstructing rapid past climate changes at high latitudes. Despite this, few records currently exist from coastal Greenlandic ice caps due to their remote nature, limiting our long-term understanding of past maritime and coastal climate variability across this rapidly changing Arctic region. Here, we reconstruct regionally representative glacier surface mass balance and climate variability over the last two thousand years (~169–2015 ce) using an ice core collected from the Nuussuaq Peninsula, west Greenland. We find indications of abrupt regional hydroclimate shifts, including an up to 20% decrease in average snow accumulation during the transition from the Medieval Warm Period (950–1250 ce) to Little Ice Age (1450–1850 ce), followed by a subsequent >40% accumulation increase from the early 18th to late 20th centuries ce. These coastal changes are substantially larger than those previously reported from interior Greenland records. Moreover, we show that the strong relationship observed today between Arctic temperature rise and coastal ice cap decay contrasts with that of the last millennium, during which periods of warming led to snowfall-driven glacial growth. Taken together with modern observations, the ice core evidence could indicate a recent reversal in the response of west Greenland ice caps to climate change.

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Fig. 1: Nuussuaq ice cap location and moisture source influences.
Fig. 2: Nuussuaq ice cap glaciological setting and estimated ice core age constraints.
Fig. 3: Optimum reconstruction of past Nuussuaq ice cap accumulation changes.
Fig. 4: Enhanced sensitivity in Nuussuaq ice cap accumulation to last-millennium climate variability.

Data availability

Ice core annual accumulation time series (Figs. 3 and 4) are publicly available via the National Oceanic and Atmospheric Administration (NOAA) Paleoclimatology Data Archive ( Depth-resolved geochemical and ice-conductivity measurements, used for time-dating of the NU ice core (for example, S, Pb, Tl, Mg and Na), are available via the National Science Foundation Arctic Data Center ( NASA Operation IceBridge data (Fig. 2a and Supplementary Section 2) can be accessed using the National Snow and Ice Data Center’s (NSIDC) IceBridge Data Portal ( Temperature reanalysis data (Fig. 4) from HadCRUT4 are available from WaterSip data are available from H.S. on request.

Code availability

Ice strain inversion source code is available at Code for post-processing and analysis of WaterSip data, and all associated statistical analyses described herein, is available from M.B.O. on request.


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Funding for retrieval and analysis of the NU ice core was provided by the US National Science Foundation (NSF) Arctic System Science Program award OPP-1205196 to S.B.D. and ARC-1205062 to B.E.S. Geospatial support for this work was provided by the Polar Geospatial Center under NSF-OPP awards 1043681 and 1559691. M.B.O. acknowledges support from the US Department of Defense National Defense Science and Engineering Graduate fellowship and an Ocean Outlook Fellowship to the Bjerknes Centre for Climate Research. L.D.T. acknowledges support from the NSF (grant no. 2021699). H.S. acknowledges support from UNINETT Sigma2 (the National Infrastructure for High Performance Computing and Data Storage in Norway; grant no. NS9054K) and the Norwegian Research Council (grant no. 262710). We thank IDDO and IDPO and M. Waszkiewicz for assistance with ice coring equipment and drilling, Polar Field Services for field support and Air Greenland for air support. We thank the students and staff of the DRI ice core group for laboratory assistance; T.J. Fudge for assistance with electrical conductivity measurements and the NSF Ice Core Facility, A. York, M. Bingham and M. Hatch for Nuussuaq ice core sampling, processing and analysis support.

Author information




M.B.O. designed the study with input from B.E.S., L.D.T. and S.B.D.; B.E.S. and S.B.D. determined the Nuussuaq ice cap site location and M.B.O., L.D.T. and S.B.D. collected and processed the NU ice core. M.B.O., J.R.M., N.C. and M.A. analysed the NU ice core chemistry. NU ice core dating was led by M.B.O., B.E.S. designed the ice strain inversion with input from M.B.O., and H.S. conducted the NU ice cap moisture source analysis. Data analysis and interpretation were led by M.B.O., who wrote the manuscript with input from B.E.S., L.D.T. and S.B.D. All authors read and commented on the manuscript.

Corresponding author

Correspondence to Matthew B. Osman.

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Competing interests

The authors declare no competing interests.

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Peer review information Nature Geoscience thanks Joshua Cuzzone, Horst Machguth and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Primary Handling Editor(s): James Super.

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Extended data

Extended Data Fig. 1 Comparison of coastal West Greenland terrestrial temperature proxies.

a, Sediment core-derived time series (all shown with positive orientation relative to increasing temperature) are numbered from 1-11, representing most-northerly to most-southerly situated, with corresponding coastal locations shown in (b). All sediment records are limited to sites containing at least 10 data points during the Common Era. (1.) First Principal Component (“PC1”) of physical properties measured from the Sikuiui Lake sediment core16. (2.) Reconstructed July lake temperatures from chironomid-abundance assemblages from North Lake, CWG (ref. 61). (3.) Lake N-3 δ2H of C28 n-alkanoic acids, produced by terrestrial plants19. (4.) Organic matter (OM) fluxes for SS1381 (ref. 62). (5.) PC3 of parameters reflecting lake-bottom redox variability (Mn, Mn/Fe, Ca/Ti and grey scale; ref. 17). (6.) Alkenone unsaturation (\(U_{37}^K\)) from Braya Sø63. (7.) First canonical correspondence (CC1) of SS16 diatom assemblages64. (8.) Residue-on-ignition (ROI) from the NAUJG1-1 lake sediment core65. (9.) Pollen flux to Lake Igaliku, CWG18. (10.) Scoop Lake temperatures via the δ18O content of chironomids20. (11.) Biogenic silica abundances in Lake N14 (ref. 66). Red and blue ranges represent the mean (μ) and standard deviation (σ) range of MWP (red) and LIA (blue) values. Purple probability density functions at top show outlet glacier distal-moraine age-estimates (where “distal” refers to the most advanced Common Era glacier terminus positions identified at each site) from Nuussuaq Peninsula, Disko Island, and Baffin Island13,14,15.

Extended Data Fig. 2 Synchronization of the Nuussuaq ice core to previously published, well-dated interior Greenland Ice Sheet ice core geochemical records.

Shown for comparison alongside the NU record is the NGRIP2comp. (NGRIP2 prior to 1257 CE, composited to NEEM-2011-S1 record thereafter; ref. 52) and NEEM-2011-S1 records for (a) Pb and (b) non-sea-salt sulfur (nssS). Alternating-current Electrical Conductivity Measurements (ECM-AC), conducted at high-resolution (1 mm) along the NU core profile, are shown for the deepest (oldest) portion of the core alongside NGRIP2 ECM measurements52 and NEEM-2011-S1 nssS (ref. 54). Tie point ages identified along the core length are shown as vertical grey lines. Age scales for the NGRIP2 and NEEM-2011-S1 records follow ref. 52.

Extended Data Fig. 3 Minimized age-constraint offsets in the least complex Nuussuaq age-model.

a, Recovered age-depth scale for the least complex accumulation history model, alongside the corresponding age-depth picks. Error bars on the age-depth picks, and differences with the recovered age-depth model, is not visible at this scale. b, Age differences between the least complex recovered age-depth scale and the age-depth constraints (circles with bars), with the prescribed relative uncertainties shown as the vertical bars.

Extended Data Fig. 4 Consistent Nuussuaq ice cap accumulation histories under varying prescribed reference ice thicknesses and accumulation rates.

a, Predicted (that is, forward modeled) age-depth scales under three different reference ice thickness (H0 = Hopt = 141 mice and H0 = Hopt ± 10 mice) scenarios and a constant reference accumulation rate (\(\dot b_0\) = \(\dot b_{opt}\) = 0.325 mice yr−1). The depth-age-constraints (“Layer Picks”, Fig. 2b) are shown for comparison, showing all corresponding age-scales agree well at shallow depths, but diverge noticeably at depths greater than approximately 100 mice where large variations in depth-ages are increasingly dictated by small variations in ice strain. b, Recovered NU accumulation histories estimates for the three model-predicted age-depth scales shown in (a), illustrating the sensitivity of our NU accumulation history to H0. For H0 = 131 mice, accumulation rate must increase over much of the core’s time-history to compensate for the added strain implied by the thinner ice cap. The converse is true for H0 = 151 mice, where the annual layers must be relatively thin to compensate for lower strain. The deviations from the global optimum accumulation rate for H0 = 131 mice and H0 = 151 mice each imply enhanced model complexity although, importantly, the form of variability over the last millennium appears robust across all models.

Extended Data Fig. 5 Industrial-era time series analysis of coastal West Greenland hydroclimate variability.

a, Danish Meteorological Institute-derived precipitation anomalies at Pituffik and Nuuk compared to (b) WaterSip-inferred NU ice cap precipitation anomalies. Thin lines show precipitation from the ERA-20C reanalysis67, illustrating long term increasing CWG trends. d, Station-based mean-annual NAO index68. e, Baffin Bay wintertime (FMA) sea ice extent (“SIE”; 40-80˚N, 80-45˚W). f, Danish Meteorological Institute-derived summertime CWG temperatures from ref. 69 (note site locations in the inset). g, The NU annual-resolution accumulation history and (h) melt percent history. Panel (i) shows overlapping annual resolution Devon and Agassiz Ice Cap melt histories alongside NU melt, with site locations for time series shown here and in Fig. 4d at left for reference. All annual and 10-yr lowpass filtered data are shown using thin and thick lines, respectively. Shown at top for comparison is the estimated industrial-era onset and emergence timing of Arctic temperature70 and CWG melt (light grey; ref. 2). Note the strong covariation (r = 0.69; p < 0.001) between NU mass balance and coastal summertime temperatures prior to local melt-emergence.

Extended Data Fig. 6 Seasonal moisture source estimates for the Nuussuaq Ice Cap.

a, The WaterSip-diagnosed seasonal cycle of moisture-source 2 m surface air temperature (yellow) and Baffin Bay (defined 85-45˚W and 40-80˚N) sea ice extent from ERA-Interim during the same period (“SIE”; grey). Thick lines denote the mean and shaded bands the 1σ range. b, WaterSip-estimated NU precipitation seasonality (median ± 1 median-absolute-deviation) based on ERA-Interim precipitation60. Also shown are monthly precipitation rates from the Danish Meteorological Institute71 weather-stations in Nuuk (64˚N), Qaqortoq (60˚N) and Pituffik (76˚N; see also inset Greenland map to the right of (b)). Clyde River data are from ref. 72. c, Percent contribution of the NU annual moisture budget per degree latitude-longitude, inferred from WaterSip (Section 6.2) during January-February-March (JFM; CWG precipitation minimum). d, As in (c), but for July-August-September (JAS; CWG precipitation maximum). (e) and (f): Percent moisture contribution as a function of distance from the NU ice core site, shown for JFM and JAS, respectively (see also Fig. 1b-c). Bar plots in (e) and (f) and inset globe to the right of (f), are color-coded by distance from the NU ice core site.

Extended Data Fig. 7 Relationships between WaterSip-modeled Nuussuaq precipitation and moisture source temperature (a-b) and Baffin Bay sea-ice extent (SIE) (c-d) at mean-annual (a,c) and mean-monthly (b,d) resolutions.

Points in (a) are color-coded with respect to Baffin SIE (1980-2013 CE), and in (b) with respect to moisture source temperature (1980-2013 CE). All monthly anomalies have been seasonally detrended. Both linear correlations shown in (a) are significant at p < 0.0001 via the method of ref. 24. Note different x-scales in the top vs. bottom panels.

Extended Data Fig. 8 Mean-annual, summertime, and wintertime Nuussuaq precipitation sensitivity to temperature and sea-ice changes.

Shown in the left panels are WaterSip-diagnosed (a) annual, (b) JAS, and (c) JFM NU evaporation-rate differencing maps for years with anomalously high- vs. low snowfall accumulation over the NU ice cap. Anomalous snow accumulation years are defined as years when model-estimated snowfall deviates greater than 0.5σ and less than −0.5σ, where σ denotes transformation to z-score units relative to the observational period 1980-2013 CE. Red and blue lines shown in the left panel denote the corresponding mean sea ice edge position (defined as the 15% sea ice concentration isopleth) for all anomalously high and low NU snow-accumulation years, respectively. The right panels denote the corresponding SW Greenland temperature69 and Baffin Bay (defined 40-80˚N, 80-45˚W) sea ice extent (SIE) anomalies (shown in z-score units for visualization) for anomalously high (red) and low (blue) NU snow-accumulation years. Box plot center lines denote the mean, dark shading the ±1σ range, and light shading the 95% confidence interval. Collectively, the results suggest that although temperature is most important in dictating NU snow accumulation on a year-round basis, Baffin Bay SIE may also play a non-negligible secondary role by dictating wintertime NU snow-accumulation.

Extended Data Fig. 9 Sensitivity of modelled and observed Nuussuaq accumulation changes to temperature.

a, WaterSip precipitation sensitivity to moisture source temperature. b, NU accumulation vs. CWG Danish Meteorological Institute71 mean annual surface temperature. c, Observed NU accumulation sensitivity to three different pan-Arctic surface air temperature estimates: the NOAA 20th Century Reanalysis (NOAA20C; ref. 73), the NASA-GISS product74, and the HadCRUT4 product50. Analyzed values in (b) and (c) are 10-yr mean-binned resolution, ignoring the most-recent post-1980 GIC melt-emergence period. All dependent- and independent-variable uncertainties are ±1σ (n = 10 years) and the shaded bands the 95% confidence intervals of the weighted regression. d, Bootstrap-derived (random sampling with replacement; n = 1,000 iterations) sensitivity of NU accumulation per degree warming. Confidence ranges are, from lightest to darkest, 2.5-97.5th, 10-90th, 25-75th, and 50th percentiles.

Extended Data Fig. 10 Comparison of regional temperature and the North Atlantic Oscillation during the Common Era.

a, From top: comparison of NU ice core accumulation (this study) against Arctic-2k temperature25; ice core δ15N-δ40Ar gas-derived surface air temperature46; interior Greenland ice core borehole thermometer-derived surface air temperatures45; alkenone-based sea-surface temperature from MD99-2275 and A07-036 (inverted y-axis) showing divergent MWP warming/cooling, respectively47; a bi-proxy (Scotland speleothem and Moroccan tree ring) NAO reconstruction35; a multiproxy model-tested NAO reconstruction75; a tree-ring based NAO reconstruction42; and a station-based NAO index68. All NAO series are shown at 30-yr lowpass resolution for visual comparison. Vertical light red and blue shaded intervals are the MWP and LIA, respectively. Panels (b) and (c) show spatial correlation maps (1900-2015 CE) for the mean annual NAO index of ref. 68 vs. NOAA20C mean annual surface air temperatures (SAT)73 and HadISST v1.1 mean annual sea surface temperature (SST)76, respectively. Site locations from (a) are highlighted in (b); note the predominance of Baffin Bay-centric sites from the Arctic-2k compilation25.

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Supplementary Sections 1–5, Table 1 and references.

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Osman, M.B., Smith, B.E., Trusel, L.D. et al. Abrupt Common Era hydroclimate shifts drive west Greenland ice cap change. Nat. Geosci. (2021).

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