Topographic Setting Drives the Imprint of the Madden–Julian Oscillation ( MJO ) on Tree Growth in the Northern Sierra Nevada

Abstract

Understanding how large‐scale tropical climate patterns, such as the Madden–Julian Oscillation (MJO), influence tree growth is crucial for improving regional climate projections and water resource management. We investigate whether tree growth from conifer forests in the northern Sierra Nevada, United States can serve as a proxy for MJO variability. Increment cores were collected from Pinus jeffreyi (site = JSJ; n = 21) and Abies magnifica (site = JSR; n = 44) trees growing on opposite slopes, resulting in chronologies that spanned 1690–2022 and 1673–2022, respectively. We used these records to assess climate drivers of tree growth from local (e.g., temperature, precipitation, drought) to broad scales (e.g., ocean–atmosphere conditions over the Indo‐Pacific, MJO indices). Both records exhibit significant correlations ( p u ) and meriodional ( v ) winds, sea‐level pressure (SLP) and sea surface temperature (SST), particularly across the tropical Pacific, while the JSR (from a north‐east facing slope) shows more localised responses. Notably, JSJ demonstrated significant correlations with multiple MJO indices ( p PACS: 0000, 1111 MSC2000 Classification: 0000, 1111.

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