 volume from CryoSat-2 measurements for the months November (minimum volume) to April (maximum volume). Number in the markers indicate the ranking of each month for the seven years of the data record, with 1 representing the smallest volume and 7 the largest. (b) The shaded area denotes the region where ice volume was determined.
Snow on Sea Ice
Snow plays several critical roles in the mass balance of Arctic sea ice. During the winter growth season, snow insulates the ocean from the atmosphere, dampening heat fluxes and reducing sea ice growth. In spring, snow reflects more than 80% of the incoming solar radiation, delaying ice melt. Snow can also contribute to ice growth after flooding and refreezing, leading to formation of snow ice (Granskog et al., 2017). As the melt season progresses, freshwater from snowmelt enables the formation of ponds on the sea ice.
Prior to the 1990s, observations of snow on Arctic sea ice were limited to in situ measurements. Warren et al. (1999) compiled many of these observations into a climatology. Since the 1990s, new approaches to measure snow accumulation have rapidly emerged, including improved instruments for in situ and autonomous observations and remote sensing techniques for retrieving snow depth. Field observations from recent years continue to underscore significant regional and inter-annual variability in Arctic snow on sea ice conditions. Figure 6 shows the historical snow depth climatology (background) plus a compilation of recent airborne snow depth measurements collected between March and May in 2009-2012 and 2014-2015 (lines), and in situ measurements made in 2015 and 2017 (individual points). Mean snow depths range from ~0.05 m to 0.55 m as shown. Compared to the climatology, these data indicate that there has been an overall decrease in snow depths in the western Arctic at the end of winter, potentially associated with later sea ice formation in the autumn and the shift from MY to FY ice. (Webster et al., 2014). Airborne observations confirm that snow on first year ice is thinner than that on multi-year ice (Kurtz and Farrell, 2011; Blanchard-Wrigglesworth et al., 2015).
Fig. 6. Snow depth on Arctic sea ice at the end of winter, prior to melt onset. Recent in situ measurements (stars) at a variety of field sites, as well as airborne observations (dots along multiple flight survey lines) are overlaid on the climatological mean snow depth for the months of March and April (adapted from Warren et al., 1999).
Blanchard-Wrigglesworth, E., S. L. Farrell, T. Newman, and C. M. Bitz, 2015: Snow cover on Arctic sea ice in observations and an Earth System Model. Geophys. Res. Lett., doi: 10.1002/2015GL066049.
Fetterer, F., K. Knowles, W. Meier, and M. Savoie, 2002, updated daily: Sea Ice Index. Boulder, Colorado USA: National Snow and Ice Data Center. http://dx.doi.org/10.7265/N5QJ7F7W.
Granskog, M. A., A. Rösel, P. A. Dodd, D. Divine, S. Gerland, T. Martma, and M. J. Leng, 2017: Snow contribution to first-year and second-year Arctic sea ice mass balance north of Svalbard. J. Geophys. Res.-Oceans, 22, doi: 10.1002/2016JC012398.
Kurtz, N. T., and S. L. Farrell, 2011: Large-scale surveys of snow depth on Arctic sea ice from Operation IceBridge. Geophys. Res. Lett., 38, L20505, doi: 10.1029/2011GL049216.
Kwok, R., and D. A. Rothrock, 2009: Decline in Arctic sea ice thickness from submarine and ICESat records: 1958-2008. Geophys. Res. Lett., 36, doi: 10.1029/2009GL039035.
Laxon, S. W., K. A. Giles, A. L. Ridout, D. J. Wingham, R. Willatt, R. Cullen, R. Kwok, A. Schweiger, J. Zhang, C. Haas, S. Hendricks, R. Krishfield, N. Kurtz, S. Farrell, and M. Davidson, 2013: CryoSat-2 estimates of Arctic sea ice thickness and volume. Geophys. Res. Lett., 40, 732-737, doi: 10.1002/grl.50193.
Lindsay, R., and A. Schweiger, 2015: Arctic sea ice thickness loss determined using subsurface, aircraft, and satellite observations. The Cryosphere, 9, 269-283.
Maslanik, J., J. Stroeve, C. Fowler, and W. Emery, 2011: Distribution and trends in Arctic sea ice age through spring 2011. Geophys. Res. Lett., 38, d