Exploring landscape sensitivity to the Pacific Trade Wind Inversion on the subsiding island of Hawaii

Abstract

The interaction of the subsiding limb of the Hadley circulation and the easterly North Pacific Trade Winds establishes a persistent thermal inversion at about 2000 m above sea level in the subtropical Pacific. The inversion restricts convective rainfall to the lower elevations of the windward flank of the island of Hawaii, creating an order-of-magnitude vertical rainfall gradient, as well as high interbasin variability in precipitation. In the high-rainfall zone, streams are incised tens to hundreds of meters below the surface of the volcanic shield. We use a digital elevation model and 1-D numerical modeling to assess whether deep incision on the flank of Mauna Kea is tied to the elevation of the trade wind inversion. The 83 channels examined can be well fit in aggregate by all models that account for differences in precipitation between basins; specifically, the maximum depth of incision in each drainage is a power function of precipitation-weighted drainage area with an exponent of~½. Individual longitudinal stream profiles are generally better fit by models that acknowledge both along-channel precipitation variability and the subsidence of the island through that gradient, but this relationship is not clearly demonstrable for many channels. We argue that island subsidence through the dry-to-wet precipitation gradient has resulted in less cumulative discharge in the lower reaches of the drainages over their lifetime, relative to a nonsubsiding case. This reduces differential erosion between the wet and dry reaches by 20-30% over 300 kyr, making the longitudinal profiles less sensitive to the very strong climate gradient.

Simulating the evolution of the topography–climate coupled system

“…13). This argument is also in accordance with an earlier study about the detachment-limited condition (Whipple and Tucker, 1999). Note that the inverse relationship between the imposed P and the resultant relief is found to be nonlinear (as P linearly grows from 50 to 100 and 150 mm d −1 , relief reduces nonlinearly, approximately from 2.7 to 1.5 and 1 km).…”

The Dynamics of Channel Slope, Width, and Sediment in Actively Eroding Bedrock River Systems

“…Yet when the model assumptions are tested with independent field evidence, disparate conclusions are reached. In some cases, researchers have interpreted that the model captures the dynamics of mountainous rivers reasonably well (Crosby & Whipple, ; Cyr et al, ; DiBiase et al, ; Duvall et al, ; Ouimet et al, ; Snyder et al, ), yet in other studies, researchers found that the model fails to predict morphological changes associated with a significant variation in forcing (Cowie et al, ; Lague, ; Lavé & Avouac, ; Ward & Galewsky, ; Whittaker et al, ; Yanites et al, ). Developing new quantitative approaches that can bridge the gaps in the observational tests of theory is needed to improve constraints on how topography evolves in a dynamic Earth system.…”

Influence of Spatial Rainfall Gradients on River Longitudinal Profiles and the Topographic Expression of Spatially and Temporally Variable Climates in Mountain Landscapes

“…Within large river basins, these differences may be substantial. Exposure to orographic precipitation patterns is expected to systematically affect river profile concavity; increases in precipitation with distance upstream lowers profile concavity, while the opposite trend increases profile concavity (Han et al, 2014(Han et al, , 2015Roe et al, 2002Roe et al, , 2003Ward & Galewsky, 2014). Changes in concavity driven by temporal changes in orographic precipitation patterns require longitudinally variable amounts of incision.…”