Energy surpluses and deficits propel all meteorological phenomena. Fluids, in the form of the ocean and the atmosphere, have the mobility to re-distribute energy globally. This redistribution occurs as ocean currents, winds and storm systems. Because of its prevalence, high specific heat and ability to exist in and transition between any of three physical states on (or near) earth’s surface, water is the most important component of global heat transfer. Changes to the current energy balance will be reflected in ocean and atmospheric redistribution patterns- affecting the transport of water as vapor, condensate and solid, which is traceable using stable isotopes of hydrogen and oxygen.

We intend to disentangle the relative importance of known climate factors, including sea ice, on the isotopic signature of storm events on the North Slope of Alaska in an effort to more fully understand the effect of sea ice presence or absence on the arctic climate system. This work has two motivations: first, understanding the future significance of the observed sea ice decline and second, to gain a deeper understanding of the controls on isotopes within the current climate regime, potentially link these to decadal scale pressure oscillations, and finally apply these findings to paleoclimate studies through analysis of ice cores.

Regarding the first motivation- recent decades have changed the Arctic hydrological cycle. There has been a measureable decline in Arctic sea ice concentration and extent ({{29 Kurita,Naoyuki 2011}}, {{30 Stroeve,Julienne 2007}}). This is significant, as sea ice formation and melting are drivers for two important energy circulators: the ocean and the atmosphere. Sea ice formation powers the North Atlantic Deepwater formation (NADW), the greatest source of surface water into the deep. Atmospherically, the presence of sea ice and the extent to which it melts affects the local albedo and thus the radiation balance. The radiation balance affects local atmospheric temperature, ocean-atmosphere heat exchange and temperature gradients from the equator to the North Pole{{21 Dagmar,Budikova 2009}}. Presence of a strong (or weak) temperature gradient from the mid-latitudes to the arctic affects wind and storm patterns, changing the distance over which moist air can travel ({{21 Dagmar,Budikova 2009}})  and hence the location where it is precipitated.

To understand the effect of these changes to the hydrological cycle, we need a detailed understanding of the trajectory and conditions at phase changes experienced by moist airmasses on the journey from the vapor source to the precipitation site. Fortunately, both hydrogen and oxygen have multiple stable isotopes: ¹H, ²H ,¹⁶O,  ¹⁷O and ¹⁸O. Because of differences in mass, and therefore diffusion speeds, phase change energies and bonding energies, molecules containing a water molecule containing a heavy isotope of either oxygen or hydrogen (²H, ¹⁷O or ¹⁸O) will respond differently to a phase change than water molecules comprised of only the light isotopes. This means that the isotopic signature of precipitation contains important information about the conditions at the vapor source, within the cloud and during precipitation.

There are nine possible combinations of the stable isotopes of oxygen and hydrogen. However, only three appear in practically measureable quantities: H₂¹⁶O, HD¹⁶O and H₂¹⁸O. The isotopic signatures are expressed as a ratio to Vienna mean standard ocean water (VSMOW) in units of “per mille”, signified as δD or δ¹⁸O. The expressions for the deuterium and oxygen-18 signatures are shown below.

Regarding the second motivation- because isotopes reflect the prevailing atmospheric and oceanic conditions, stable isotopes of hydrogen and oxygen in water have utility as meteorological tracers and paleoclimate indicators. In the latter area of study they’ve been used as a rough paleothermometer (Daansgard et al 1969, 1982). This is reasonable, as the former area of study has shown a linear relationship between temperature and isotope signature ({{28 Dansgaard,W. 1964}}, Daansgard et al 1973, Lorius and Merlivat, 1977) under equilibrium conditions. However, the isotopic signature is also dependent on other factors. As stated, conditions at the vapor source affect the initial vapor, conditions within the storm cloud affect the extent to which heavy isotopes are condensed and lost as precipitation, and conditions at the precipitation site will influence the degree to which the precipitation exchanges with the surrounding water vapor. The aforementioned conditions include relative humidity, temperature, sub- or super-saturation, upward velocity, and wind speed. If we can clearly understand what the isotopic signature of precipitation is indicating about specific storm systems, and storm system types could be linked to trends in decadal scale oscillations, it would be an asset to modern meteorology, paleoclimatology and climate projections.

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Two tapes from Van Party Tapes in Marquette, MI. One is Sycamore Smith/ Troy Graham, the other is Keweenawsomefest 2012 split between Gratiot Lake Road and Troy Graham. Excited to drive so I can listen to them!