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Matthew Alkire

Senior Oceanographer

Email

malkire@apl.washington.edu

Phone

206-897-1623

Department Affiliation

Polar Science Center

Education

B.S. Marine Sciences, Richard Stockton College of New Jersey, 2003

M.S. Chemical Oceanography, Florida Institute of Technology, 2005

Ph.D. Oceanography, Oregon State University, 2010

Publications

2000-present and while at APL-UW

On the seasonal cycles observed at the continental slope of the eastern Eurasian Basin of the Arctic Ocean

Baumann, T.M., and 7 others including M.B. Alkire, "On the seasonal cycles observed at the continental slope of the eastern Eurasian Basin of the Arctic Ocean," J. Phys. Oceanogr., 48, 1451-1470, doi:10.1175/JPO-D-17-0163.1, 2018.

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1 Jul 2018

The Eurasian Basin (EB) of the Arctic Ocean is subject to substantial seasonality. We here use data collected between 2013 and 2015 from six moorings across the continental slope in the eastern EB and identify three domains, each with its own unique seasonal cycle: 1) The upper ocean (<100 m), with seasonal temperature and salinity differences of Δθ = 0.16°C and ΔS = 0.17, is chiefly driven by the seasonal sea ice cycle. 2) The upper-slope domain is characterized by the influence of a hydrographic front that spans the water column around the ~750-m isobath. The domain features a strong temperature and moderate salinity seasonality (Δθ = 1.4°C; ΔS = 0.06), which is traceable down to ~600-m depth. Probable cause of this signal is a combination of along-slope advection of signals by the Arctic Circumpolar Boundary Current, local wind-driven upwelling, and a cross-slope shift of the front. 3) The lower-slope domain, located offshore of the front, with seasonality in temperature and salinity mainly confined to the halocline (Δθ = 0.83°C; ΔS = 0.11; ~100–200 m). This seasonal cycle can be explained by a vertical isopycnal displacement (ΔZ ~ 36 m), arguably as a baroclinic response to sea level changes. Available long-term oceanographic records indicate a recent amplification of the seasonal cycle within the halocline layer, possibly associated with the erosion of the halocline. This reduces the halocline’s ability to isolate the ocean surface layer and sea ice from the underlying Atlantic Water heat with direct implications for the evolution of Arctic sea ice cover and climate.

Combining physical and geochemical methods to investigate lower halocline water formation and modification along the Siberian continental slope

Alkire, M.B., I. Polyakov, R. Rember, A. Pnyushkov, V. Ivanov, and I. Ashik, "Combining physical and geochemical methods to investigate lower halocline water formation and modification along the Siberian continental slope," Ocean Sci., 13, 983-995, doi:10.5194/os-13-983-2017, 2017.

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24 Nov 2017

A series of cross-slope transects were occupied in 2013 and 2015 that extended eastward from St. Anna Trough to the Lomonosov Ridge. High-resolution physical and chemical observations collected along these transects revealed fronts in the potential temperature and the stable oxygen isotopic ratio that were observed north of Severnaya Zemlya (SZ). Using linear regressions, we describe mixing regimes on either side of the front that characterize a transition from a seasonal halocline to a permanent halocline. This transition describes the formation of lower halocline water (LHW) and the cold halocline layer via a mechanism that has been previously postulated by Rudels et al. (1996). Initial freshening of Atlantic Water (AW) by sea-ice meltwater occurs west of SZ, whereas higher influences of meteoric water and brine result in a transition to a separate mixing regime that alters LHW through mixing with overlying waters and shifts the characteristic temperature–salinity bend from higher (34.4  ≤  S  ≤  34.5) toward lower (34.2  ≤  S  ≤  34.3) salinities. These mixing regimes appear to have been robust since at least 2000.

On the geochemical heterogeneity of rivers draining into the straits and channels of the Canadian Arctic Archipelago

Alkire, M.B., A.D Jacobson, G.O. Lehn, R.W. Macdonald, and M.W. Rossi, "On the geochemical heterogeneity of rivers draining into the straits and channels of the Canadian Arctic Archipelago," J. Geophys. Res., 122, 2527-2547, doi:10.1002/2016JG003723, 2017.

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12 Oct 2017

Ten rivers across northern Canada and the Canadian Arctic Archipelago (CAA) were sampled during spring 2014 and summer 2015 to investigate their geochemical heterogeneity for comparison against larger North American (i.e., Mackenzie and Yukon Rivers) and Siberian rivers. In general, rivers draining the western and/or northern regions of the study area have higher solute concentrations and lower 87Sr/86Sr ratios compared to rivers draining the eastern and/or southern regions. The inorganic geochemical signatures largely reflect the bedrock geology, which is predominately carbonate in the western and/or northern regions and silicate in the eastern and/or southern regions. Riverine δ18O values primarily correlate with latitude, with only a few exceptions. Measurements of total alkalinity (TA) were combined with a regional analysis of bedrock geology and extrapolated to produce a range for the mean characteristic TA of rivers draining into the straits and channels of the CAA (628–819 μeq kg-1). Combining this estimate with contributions from the Mackenzie River yields a revised North American river runoff TA of 935–1182 μeq kg-1, which is much lower than that of the Mackenzie River (1540 μeq kg-1). This lower concentration suggests that TA may not be used to distinguish between North American and Siberian river contributions in regions such as Davis Strait.

More Publications

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center
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